florida lakewatch report for apopka in orange county using ... · 1. identify your lake’s lake...
TRANSCRIPT
![Page 1: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/1.jpg)
1
Florida LAKEWATCH Report for Apopka in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 2: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/2.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 57 - 114 81 (8)
Total Nitrogen (µg/L) 2654 - 4696 3524 (8)
Chlorophyll- uncorrected (µg/L) 44 - 104 60 (8)
Secchi (ft) 0.6 - 1.5 1.0 (8)
Secchi (m) 0.2 - 0.5 0.3 (8)
Color (Pt-Co Units) 18 - 29 23 (5)
Specific Conductance (µS/cm@25 C) 324 - 467 376 (5)
Lake Classification Clear Hardwater
![Page 3: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/3.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Apopka
GNIS Number 293912
Latitude 28.6655
Longitude -81.6302
Water Body Type Lake
Surface Area (ha and acre) 12518 ha or 30932.0 acre
Period of Record (year) 2006 to 2019
Lake Trophic Status (CHL) Hypereutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 81 (57 to 114)
TN Zone TN5
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 3524 (2654 to 4696)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 4: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/4.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 5: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/5.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 6: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/6.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 7: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/7.jpg)
1
Florida LAKEWATCH Report for Arnold in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 8: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/8.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 14 - 40 23 (19)
Total Nitrogen (µg/L) 454 - 947 642 (19)
Chlorophyll- uncorrected (µg/L) 9 - 40 21 (19)
Secchi (ft) 2.8 - 8.2 4.9 (19)
Secchi (m) 0.9 - 2.5 1.5 (19)
Color (Pt-Co Units) 11 - 15 13 (10)
Specific Conductance (µS/cm@25 C) 138 - 174 158 (8)
Lake Classification Clear Hardwater
![Page 9: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/9.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Arnold
GNIS Number 277957
Latitude 28.5303
Longitude -81.3413
Water Body Type Lake
Surface Area (ha and acre) 11 ha or 27.2 acre
Period of Record (year) 1990 to 2018
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 23 (14 to 40)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 642 (454 to 947)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 10: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/10.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 11: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/11.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 12: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/12.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 13: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/13.jpg)
1
Florida LAKEWATCH Report for Avalon in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 14: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/14.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 8 - 22 13 (18)
Total Nitrogen (µg/L) 728 - 1144 872 (18)
Chlorophyll- uncorrected (µg/L) 4 - 14 7 (18)
Secchi (ft) 3.5 - 8.9 5.8 (18)
Secchi (m) 1.1 - 2.7 1.8 (18)
Color (Pt-Co Units) 26 - 95 43 (14)
Specific Conductance (µS/cm@25 C) 76 - 107 91 (12)
Lake Classification Colored
![Page 15: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/15.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Avalon
GNIS Number 278004
Latitude 28.5139
Longitude -81.6404
Water Body Type Lake
Surface Area (ha and acre) 66 ha or 163.1 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 13 (8 to 22)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 872 (728 to 1144)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 16: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/16.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 17: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/17.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 18: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/18.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 19: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/19.jpg)
1
Florida LAKEWATCH Report for Baldwin in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 20: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/20.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 13 - 22 16 (12)
Total Nitrogen (µg/L) 372 - 647 508 (12)
Chlorophyll- uncorrected (µg/L) 4 - 18 9 (12)
Secchi (ft) 5.1 - 9.6 7.0 (12)
Secchi (m) 1.6 - 2.9 2.1 (12)
Color (Pt-Co Units) 11 - 18 14 (9)
Specific Conductance (µS/cm@25 C) 207 - 239 220 (4)
Lake Classification Clear Hardwater
![Page 21: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/21.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Baldwin
GNIS Number 1986929
Latitude 28.5744
Longitude -81.324
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 2000 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 16 (13 to 22)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 508 (372 to 647)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 22: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/22.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 23: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/23.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 24: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/24.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 25: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/25.jpg)
1
Florida LAKEWATCH Report for Bennett in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 26: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/26.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 12 - 23 18 (28)
Total Nitrogen (µg/L) 378 - 753 543 (28)
Chlorophyll- uncorrected (µg/L) 2 - 10 5 (28)
Secchi (ft) 4.0 - 13.3 7.2 (28)
Secchi (m) 1.2 - 4.0 2.2 (28)
Color (Pt-Co Units) 7 - 17 13 (19)
Specific Conductance (µS/cm@25 C) 131 - 227 168 (13)
Lake Classification Clear Hardwater
![Page 27: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/27.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Bennett
GNIS Number 278483
Latitude 28.5532
Longitude -81.5334
Water Body Type Lake
Surface Area (ha and acre) 10 ha or 24.7 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 18 (12 to 23)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 543 (378 to 753)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 28: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/28.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 29: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/29.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 30: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/30.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 31: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/31.jpg)
1
Florida LAKEWATCH Report for Bessie in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 32: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/32.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 5 - 10 8 (28)
Total Nitrogen (µg/L) 328 - 654 519 (28)
Chlorophyll- uncorrected (µg/L) 1 - 7 3 (28)
Secchi (ft) 7.2 - 18.1 12.5 (28)
Secchi (m) 2.2 - 5.5 3.8 (28)
Color (Pt-Co Units) 5 - 10 7 (19)
Specific Conductance (µS/cm@25 C) 339 - 404 379 (13)
Lake Classification Clear Hardwater
![Page 33: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/33.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Bessie
GNIS Number 278514
Latitude 28.4913
Longitude -81.5243
Water Body Type Lake
Surface Area (ha and acre) 63 ha or 155.7 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 8 (5 to 10)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 519 (328 to 654)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 34: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/34.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 35: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/35.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 36: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/36.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 37: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/37.jpg)
1
Florida LAKEWATCH Report for Big Sand in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 38: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/38.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 5 - 15 10 (12)
Total Nitrogen (µg/L) 441 - 599 528 (12)
Chlorophyll- uncorrected (µg/L) 1 - 7 3 (12)
Secchi (ft) 11.0 - 18.5 13.6 (12)
Secchi (m) 3.3 - 5.6 4.1 (12)
Color (Pt-Co Units) 10 - 18 14 (7)
Specific Conductance (µS/cm@25 C) 209 - 209 209 (1)
Lake Classification Clear Hardwater
![Page 39: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/39.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Big Sand
GNIS Number 278738
Latitude 28.4345
Longitude -81.4951
Water Body Type Lake
Surface Area (ha and acre) 449 ha or 1109.5 acre
Period of Record (year) 1996 to 2018
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (5 to 15)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 528 (441 to 599)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 40: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/40.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 41: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/41.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 42: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/42.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 43: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/43.jpg)
1
Florida LAKEWATCH Report for Boers in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 44: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/44.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 36 - 36 36 (1)
Total Nitrogen (µg/L) 845 - 845 845 (1)
Chlorophyll- uncorrected (µg/L) 5 - 5 5 (1)
Secchi (ft) 4.0 - 4.0 4.0 (1)
Secchi (m) 1.2 - 1.2 1.2 (1)
Color (Pt-Co Units) - (0)
Specific Conductance (µS/cm@25 C) - (0)
Lake Classification
![Page 45: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/45.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Boers
GNIS Number
Latitude 28.5298
Longitude -81.5149
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 2019 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 36 (36 to 36)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 845 (845 to 845)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 46: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/46.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 47: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/47.jpg)
1
Florida LAKEWATCH Report for Butler in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 48: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/48.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 6 - 18 12 (23)
Total Nitrogen (µg/L) 444 - 774 561 (23)
Chlorophyll- uncorrected (µg/L) 1 - 5 2 (23)
Secchi (ft) 7.5 - 19.5 11.6 (23)
Secchi (m) 2.3 - 5.9 3.5 (23)
Color (Pt-Co Units) 8 - 17 12 (17)
Specific Conductance (µS/cm@25 C) 213 - 306 247 (12)
Lake Classification Clear Hardwater
![Page 49: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/49.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Butler
GNIS Number 279743
Latitude 28.4936
Longitude -81.5485
Water Body Type Lake
Surface Area (ha and acre) 771 ha or 1905.1 acre
Period of Record (year) 1993 to 2018
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 12 (6 to 18)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 561 (444 to 774)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 50: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/50.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 51: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/51.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 52: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/52.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 53: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/53.jpg)
1
Florida LAKEWATCH Report for C in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 54: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/54.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 33 - 82 49 (13)
Total Nitrogen (µg/L) 593 - 998 770 (13)
Chlorophyll- uncorrected (µg/L) 3 - 90 40 (13)
Secchi (ft) 2.6 - 7.7 3.3 (13)
Secchi (m) 0.8 - 2.3 1.0 (13)
Color (Pt-Co Units) 20 - 28 24 (3)
Specific Conductance (µS/cm@25 C) 217 - 217 217 (1)
Lake Classification Clear Hardwater
![Page 55: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/55.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name C
GNIS Number
Latitude 28.5313
Longitude -81.3202
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1990 to 2018
Lake Trophic Status (CHL) Hypereutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 49 (33 to 82)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 770 (593 to 998)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 56: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/56.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 57: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/57.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 58: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/58.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 59: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/59.jpg)
1
Florida LAKEWATCH Report for Cane in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 60: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/60.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 13 - 15 14 (7)
Total Nitrogen (µg/L) 408 - 593 489 (7)
Chlorophyll- uncorrected (µg/L) 7 - 15 9 (7)
Secchi (ft) 6.3 - 7.9 7.1 (7)
Secchi (m) 1.9 - 2.4 2.2 (7)
Color (Pt-Co Units) 10 - 14 12 (6)
Specific Conductance (µS/cm@25 C) 147 - 187 169 (5)
Lake Classification Clear Hardwater
![Page 61: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/61.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Cane
GNIS Number 279818
Latitude 28.484
Longitude -81.4728
Water Body Type Lake
Surface Area (ha and acre) 31.8 ha or 78.6 acre
Period of Record (year) 2006 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 14 (13 to 15)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 489 (408 to 593)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 62: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/62.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 63: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/63.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 64: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/64.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 65: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/65.jpg)
1
Florida LAKEWATCH Report for Claire in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 66: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/66.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 9 - 11 10 (5)
Total Nitrogen (µg/L) 464 - 495 482 (5)
Chlorophyll- uncorrected (µg/L) 2 - 3 2 (5)
Secchi (ft) 6.4 - 9.2 7.4 (5)
Secchi (m) 1.9 - 2.8 2.3 (5)
Color (Pt-Co Units) 44 - 64 54 (5)
Specific Conductance (µS/cm@25 C) 140 - 174 161 (5)
Lake Classification Colored
![Page 67: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/67.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Claire
GNIS Number 280478
Latitude 28.6082
Longitude -81.2025
Water Body Type Lake
Surface Area (ha and acre) 8.1 ha or 20.0 acre
Period of Record (year) 2015 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (9 to 11)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 482 (464 to 495)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 68: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/68.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 69: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/69.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 70: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/70.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 71: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/71.jpg)
1
Florida LAKEWATCH Report for Conway North in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 72: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/72.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 12 10 (23)
Total Nitrogen (µg/L) 366 - 605 432 (23)
Chlorophyll- uncorrected (µg/L) 2 - 12 3 (23)
Secchi (ft) 7.3 - 16.9 13.2 (23)
Secchi (m) 2.2 - 5.1 4.0 (23)
Color (Pt-Co Units) 5 - 11 7 (16)
Specific Conductance (µS/cm@25 C) 211 - 250 236 (10)
Lake Classification Clear Hardwater
![Page 73: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/73.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Conway North
GNIS Number 280728
Latitude 28.4676
Longitude -81.3514
Water Body Type Lake
Surface Area (ha and acre) 274 ha or 677.1 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (7 to 12)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 432 (366 to 605)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 74: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/74.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 75: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/75.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 76: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/76.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 77: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/77.jpg)
1
Florida LAKEWATCH Report for Conway South in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 78: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/78.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 8 - 12 10 (24)
Total Nitrogen (µg/L) 292 - 450 380 (24)
Chlorophyll- uncorrected (µg/L) 2 - 7 3 (24)
Secchi (ft) 9.5 - 17.6 14.3 (24)
Secchi (m) 2.9 - 5.4 4.4 (24)
Color (Pt-Co Units) 5 - 12 7 (16)
Specific Conductance (µS/cm@25 C) 220 - 246 236 (10)
Lake Classification Clear Hardwater
![Page 79: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/79.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Conway South
GNIS Number 280728
Latitude 28.4569
Longitude -81.3428
Water Body Type Lake
Surface Area (ha and acre) 352 ha or 869.8 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (8 to 12)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 380 (292 to 450)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 80: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/80.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 81: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/81.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 82: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/82.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 83: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/83.jpg)
1
Florida LAKEWATCH Report for Cypress in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 84: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/84.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 13 - 29 16 (11)
Total Nitrogen (µg/L) 580 - 1190 694 (11)
Chlorophyll- uncorrected (µg/L) 4 - 43 8 (11)
Secchi (ft) 3.2 - 10.9 7.8 (11)
Secchi (m) 1.0 - 3.3 2.4 (11)
Color (Pt-Co Units) 13 - 36 21 (8)
Specific Conductance (µS/cm@25 C) 177 - 206 193 (7)
Lake Classification Clear Hardwater
![Page 85: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/85.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Cypress
GNIS Number 281221
Latitude 28.4781
Longitude -81.5643
Water Body Type Lake
Surface Area (ha and acre) 26 ha or 64.2 acre
Period of Record (year) 1996 to 2018
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 16 (13 to 29)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 694 (580 to 1190)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 86: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/86.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 87: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/87.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 88: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/88.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 89: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/89.jpg)
1
Florida LAKEWATCH Report for Down in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 90: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/90.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 10 8 (20)
Total Nitrogen (µg/L) 316 - 440 382 (20)
Chlorophyll- uncorrected (µg/L) 2 - 5 2 (20)
Secchi (ft) 8.9 - 16.4 12.7 (20)
Secchi (m) 2.7 - 5.0 3.9 (20)
Color (Pt-Co Units) 8 - 10 9 (11)
Specific Conductance (µS/cm@25 C) 234 - 290 263 (7)
Lake Classification Clear Hardwater
![Page 91: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/91.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Down
GNIS Number 281739
Latitude 28.5014
Longitude -81.5206
Water Body Type Lake
Surface Area (ha and acre) 483 ha or 1193.5 acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 8 (7 to 10)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 382 (316 to 440)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 92: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/92.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 93: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/93.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 94: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/94.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 95: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/95.jpg)
1
Florida LAKEWATCH Report for Downey in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 96: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/96.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 12 - 12 12 (1)
Total Nitrogen (µg/L) 583 - 583 583 (1)
Chlorophyll- uncorrected (µg/L) 3 - 3 3 (1)
Secchi (ft) - (0)
Secchi (m) - (0)
Color (Pt-Co Units) 39 - 39 39 (1)
Specific Conductance (µS/cm@25 C) 118 - 118 118 (1)
Lake Classification Clear Hardwater
![Page 97: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/97.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Downey
GNIS Number 299953
Latitude 28.5676
Longitude -81.2423
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 2018 to 2018
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 12 (12 to 12)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 583 (583 to 583)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 98: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/98.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 99: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/99.jpg)
1
Florida LAKEWATCH Report for Eola in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 100: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/100.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 33 - 86 49 (29)
Total Nitrogen (µg/L) 521 - 842 624 (29)
Chlorophyll- uncorrected (µg/L) 18 - 80 33 (29)
Secchi (ft) 2.9 - 5.6 3.9 (29)
Secchi (m) 0.9 - 1.7 1.2 (29)
Color (Pt-Co Units) 7 - 20 12 (16)
Specific Conductance (µS/cm@25 C) 134 - 239 174 (11)
Lake Classification Clear Hardwater
![Page 101: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/101.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Eola
GNIS Number 282234
Latitude 28.5365
Longitude -81.3739
Water Body Type Lake
Surface Area (ha and acre) 10 ha or 24.7 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 49 (33 to 86)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 624 (521 to 842)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 102: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/102.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 103: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/103.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 104: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/104.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 105: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/105.jpg)
1
Florida LAKEWATCH Report for Estelle in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 106: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/106.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 22 - 53 36 (19)
Total Nitrogen (µg/L) 479 - 1034 724 (19)
Chlorophyll- uncorrected (µg/L) 6 - 45 23 (19)
Secchi (ft) 2.3 - 7.0 3.9 (18)
Secchi (m) 0.7 - 2.1 1.2 (18)
Color (Pt-Co Units) 13 - 26 18 (8)
Specific Conductance (µS/cm@25 C) 127 - 173 148 (3)
Lake Classification Clear Hardwater
![Page 107: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/107.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Estelle
GNIS Number 282256
Latitude 28.5744
Longitude -81.3682
Water Body Type Lake
Surface Area (ha and acre) 9 ha or 22.2 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 36 (22 to 53)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 724 (479 to 1034)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 108: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/108.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 109: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/109.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 110: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/110.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 111: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/111.jpg)
1
Florida LAKEWATCH Report for Eulalia in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 112: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/112.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 13 - 17 15 (2)
Total Nitrogen (µg/L) 410 - 627 507 (2)
Chlorophyll- uncorrected (µg/L) 4 - 4 4 (2)
Secchi (ft) 8.9 - 13.4 10.9 (2)
Secchi (m) 2.7 - 4.1 3.3 (2)
Color (Pt-Co Units) - (0)
Specific Conductance (µS/cm@25 C) - (0)
Lake Classification
![Page 113: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/113.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Eulalia
GNIS Number
Latitude 28.6191
Longitude -81.3726
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 15 (13 to 17)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 507 (410 to 627)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 114: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/114.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 115: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/115.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 116: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/116.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 117: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/117.jpg)
1
Florida LAKEWATCH Report for Gatlin in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 118: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/118.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 8 - 29 16 (21)
Total Nitrogen (µg/L) 490 - 1350 824 (21)
Chlorophyll- uncorrected (µg/L) 4 - 64 13 (21)
Secchi (ft) 1.7 - 11.9 4.6 (21)
Secchi (m) 0.5 - 3.6 1.4 (21)
Color (Pt-Co Units) 7 - 17 11 (11)
Specific Conductance (µS/cm@25 C) 235 - 269 250 (8)
Lake Classification Clear Hardwater
![Page 119: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/119.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Gatlin
GNIS Number 282967
Latitude 28.493
Longitude -81.3679
Water Body Type Lake
Surface Area (ha and acre) 87 ha or 215.0 acre
Period of Record (year) 1995 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 16 (8 to 29)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 824 (490 to 1350)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 120: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/120.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 121: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/121.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 122: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/122.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 123: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/123.jpg)
1
Florida LAKEWATCH Report for Georgia in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 124: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/124.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 14 10 (30)
Total Nitrogen (µg/L) 407 - 865 633 (30)
Chlorophyll- uncorrected (µg/L) 2 - 6 4 (30)
Secchi (ft) 5.6 - 12.2 7.7 (30)
Secchi (m) 1.7 - 3.7 2.3 (30)
Color (Pt-Co Units) 6 - 27 17 (18)
Specific Conductance (µS/cm@25 C) 171 - 235 202 (12)
Lake Classification Clear Hardwater
![Page 125: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/125.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Georgia
GNIS Number 283037
Latitude 28.6034
Longitude -81.2463
Water Body Type Lake
Surface Area (ha and acre) 33 ha or 81.5 acre
Period of Record (year) 1989 to 2018
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (7 to 14)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 633 (407 to 865)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 126: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/126.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 127: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/127.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 128: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/128.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 129: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/129.jpg)
1
Florida LAKEWATCH Report for Hart in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 130: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/130.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 10 - 24 18 (15)
Total Nitrogen (µg/L) 885 - 1630 1207 (15)
Chlorophyll- uncorrected (µg/L) 3 - 6 4 (15)
Secchi (ft) 1.2 - 3.1 2.0 (15)
Secchi (m) 0.4 - 0.9 0.6 (15)
Color (Pt-Co Units) 85 - 294 180 (8)
Specific Conductance (µS/cm@25 C) 78 - 117 94 (8)
Lake Classification Colored
![Page 131: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/131.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Hart
GNIS Number 283786
Latitude 28.3704
Longitude -81.2173
Water Body Type Lake
Surface Area (ha and acre) 749 ha or 1850.8 acre
Period of Record (year) 1990 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 18 (10 to 24)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1207 (885 to 1630)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 132: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/132.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 133: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/133.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 134: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/134.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 135: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/135.jpg)
1
Florida LAKEWATCH Report for Hickorynut in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 136: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/136.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 4 - 18 10 (30)
Total Nitrogen (µg/L) 591 - 1878 767 (30)
Chlorophyll- uncorrected (µg/L) 1 - 10 3 (30)
Secchi (ft) 4.8 - 15.7 9.7 (30)
Secchi (m) 1.5 - 4.8 3.0 (30)
Color (Pt-Co Units) 11 - 94 20 (15)
Specific Conductance (µS/cm@25 C) 104 - 167 144 (10)
Lake Classification Clear Hardwater
![Page 137: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/137.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Hickorynut
GNIS Number 283971
Latitude 28.417
Longitude -81.6396
Water Body Type Lake
Surface Area (ha and acre) 217 ha or 536.2 acre
Period of Record (year) 1989 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (4 to 18)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 767 (591 to 1878)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 138: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/138.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 139: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/139.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 140: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/140.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 141: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/141.jpg)
1
Florida LAKEWATCH Report for Hickorynut South in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 142: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/142.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 9 - 23 12 (22)
Total Nitrogen (µg/L) 613 - 1140 778 (22)
Chlorophyll- uncorrected (µg/L) 2 - 11 4 (22)
Secchi (ft) 3.1 - 10.4 6.9 (22)
Secchi (m) 0.9 - 3.2 2.1 (22)
Color (Pt-Co Units) 11 - 205 33 (16)
Specific Conductance (µS/cm@25 C) 112 - 167 140 (10)
Lake Classification Clear Hardwater
![Page 143: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/143.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Hickorynut South
GNIS Number 283971
Latitude 28.4282
Longitude -81.6503
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1996 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 12 (9 to 23)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 778 (613 to 1140)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 144: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/144.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 145: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/145.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 146: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/146.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 147: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/147.jpg)
1
Florida LAKEWATCH Report for Holden in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 148: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/148.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 9 - 47 21 (27)
Total Nitrogen (µg/L) 443 - 1780 811 (27)
Chlorophyll- uncorrected (µg/L) 3 - 65 15 (27)
Secchi (ft) 1.8 - 13.6 4.6 (27)
Secchi (m) 0.5 - 4.1 1.4 (27)
Color (Pt-Co Units) 6 - 15 9 (19)
Specific Conductance (µS/cm@25 C) 186 - 280 220 (13)
Lake Classification Clear Hardwater
![Page 149: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/149.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Holden
GNIS Number 284136
Latitude 28.501
Longitude -81.3952
Water Body Type Lake
Surface Area (ha and acre) 102 ha or 252.0 acre
Period of Record (year) 1990 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 21 (9 to 47)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 811 (443 to 1780)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 150: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/150.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 151: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/151.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 152: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/152.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 153: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/153.jpg)
1
Florida LAKEWATCH Report for Hourglass in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 154: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/154.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 50 - 81 64 (20)
Total Nitrogen (µg/L) 777 - 1517 1048 (20)
Chlorophyll- uncorrected (µg/L) 41 - 87 57 (20)
Secchi (ft) 1.9 - 3.2 2.5 (20)
Secchi (m) 0.6 - 1.0 0.8 (20)
Color (Pt-Co Units) 15 - 26 20 (13)
Specific Conductance (µS/cm@25 C) 104 - 208 159 (10)
Lake Classification Clear Hardwater
![Page 155: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/155.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Hourglass
GNIS Number 284333
Latitude 28.523
Longitude -81.357
Water Body Type Lake
Surface Area (ha and acre) 6 ha or 14.8 acre
Period of Record (year) 1995 to 2018
Lake Trophic Status (CHL) Hypereutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 64 (50 to 81)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1048 (777 to 1517)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 156: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/156.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 157: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/157.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 158: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/158.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 159: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/159.jpg)
1
Florida LAKEWATCH Report for Irma in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 160: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/160.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 17 - 87 28 (15)
Total Nitrogen (µg/L) 517 - 920 672 (15)
Chlorophyll- uncorrected (µg/L) 2 - 19 7 (14)
Secchi (ft) 3.6 - 8.1 5.6 (15)
Secchi (m) 1.1 - 2.5 1.7 (15)
Color (Pt-Co Units) 17 - 69 32 (11)
Specific Conductance (µS/cm@25 C) 74 - 162 111 (9)
Lake Classification Clear Hardwater
![Page 161: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/161.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Irma
GNIS Number 284591
Latitude 28.5937
Longitude -81.2631
Water Body Type Lake
Surface Area (ha and acre) 50 ha or 123.6 acre
Period of Record (year) 1994 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 28 (17 to 87)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 672 (517 to 920)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 162: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/162.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 163: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/163.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 164: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/164.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 165: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/165.jpg)
1
Florida LAKEWATCH Report for Ivanhoe East in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 166: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/166.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 16 - 33 22 (28)
Total Nitrogen (µg/L) 530 - 896 692 (28)
Chlorophyll- uncorrected (µg/L) 4 - 38 19 (28)
Secchi (ft) 2.4 - 10.3 4.0 (28)
Secchi (m) 0.7 - 3.1 1.2 (28)
Color (Pt-Co Units) 8 - 32 12 (19)
Specific Conductance (µS/cm@25 C) 163 - 209 187 (13)
Lake Classification Clear Hardwater
![Page 167: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/167.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Ivanhoe East
GNIS Number 284639
Latitude 28.5652
Longitude -81.3751
Water Body Type Lake
Surface Area (ha and acre) 44 ha or 108.7 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 22 (16 to 33)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 692 (530 to 896)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 168: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/168.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 169: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/169.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 170: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/170.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 171: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/171.jpg)
1
Florida LAKEWATCH Report for Ivanhoe Middle in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 172: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/172.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 17 - 36 25 (28)
Total Nitrogen (µg/L) 474 - 881 635 (28)
Chlorophyll- uncorrected (µg/L) 9 - 30 18 (28)
Secchi (ft) 2.8 - 9.0 4.7 (28)
Secchi (m) 0.9 - 2.7 1.4 (28)
Color (Pt-Co Units) 10 - 26 13 (19)
Specific Conductance (µS/cm@25 C) 166 - 205 184 (13)
Lake Classification Clear Hardwater
![Page 173: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/173.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Ivanhoe Middle
GNIS Number 284639
Latitude 28.5635
Longitude -81.3795
Water Body Type Lake
Surface Area (ha and acre) 28 ha or 69.2 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 25 (17 to 36)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 635 (474 to 881)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 174: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/174.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 175: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/175.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 176: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/176.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 177: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/177.jpg)
1
Florida LAKEWATCH Report for Ivanhoe West in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 178: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/178.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 11 - 39 24 (27)
Total Nitrogen (µg/L) 365 - 903 618 (27)
Chlorophyll- uncorrected (µg/L) 5 - 37 17 (27)
Secchi (ft) 2.7 - 8.9 4.7 (27)
Secchi (m) 0.8 - 2.7 1.4 (27)
Color (Pt-Co Units) 7 - 26 12 (19)
Specific Conductance (µS/cm@25 C) 172 - 198 188 (13)
Lake Classification Clear Hardwater
![Page 179: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/179.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Ivanhoe West
GNIS Number 284639
Latitude 28.5655
Longitude -81.3804
Water Body Type Lake
Surface Area (ha and acre) 28 ha or 69.2 acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 24 (11 to 39)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 618 (365 to 903)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 180: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/180.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 181: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/181.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 182: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/182.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 183: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/183.jpg)
1
Florida LAKEWATCH Report for Jessamine in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 184: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/184.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 11 - 20 16 (9)
Total Nitrogen (µg/L) 740 - 943 830 (9)
Chlorophyll- uncorrected (µg/L) 8 - 20 16 (9)
Secchi (ft) 2.5 - 6.1 3.9 (9)
Secchi (m) 0.8 - 1.9 1.2 (9)
Color (Pt-Co Units) - (0)
Specific Conductance (µS/cm@25 C) - (0)
Lake Classification
![Page 185: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/185.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Jessamine
GNIS Number 284776
Latitude 28.4832
Longitude -81.3846
Water Body Type Lake
Surface Area (ha and acre) 124 ha or 306.4 acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 16 (11 to 20)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 830 (740 to 943)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 186: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/186.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 187: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/187.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 188: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/188.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 189: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/189.jpg)
1
Florida LAKEWATCH Report for Jessamine North in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 190: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/190.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 15 - 25 21 (9)
Total Nitrogen (µg/L) 741 - 1162 977 (9)
Chlorophyll- uncorrected (µg/L) 13 - 31 22 (9)
Secchi (ft) 2.1 - 4.0 2.9 (9)
Secchi (m) 0.6 - 1.2 0.9 (9)
Color (Pt-Co Units) - (0)
Specific Conductance (µS/cm@25 C) - (0)
Lake Classification
![Page 191: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/191.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Jessamine North
GNIS Number 284776
Latitude 28.4898
Longitude -81.3821
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 21 (15 to 25)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 977 (741 to 1162)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 192: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/192.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 193: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/193.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 194: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/194.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 195: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/195.jpg)
1
Florida LAKEWATCH Report for Jessamine South in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 196: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/196.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 14 - 26 20 (13)
Total Nitrogen (µg/L) 615 - 1081 768 (13)
Chlorophyll- uncorrected (µg/L) 5 - 28 14 (13)
Secchi (ft) 2.6 - 8.9 4.5 (13)
Secchi (m) 0.8 - 2.7 1.4 (13)
Color (Pt-Co Units) 10 - 14 12 (5)
Specific Conductance (µS/cm@25 C) 181 - 204 195 (5)
Lake Classification Clear Hardwater
![Page 197: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/197.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Jessamine South
GNIS Number 284776
Latitude 28.4767
Longitude -81.3894
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 20 (14 to 26)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 768 (615 to 1081)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 198: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/198.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 199: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/199.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 200: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/200.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 201: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/201.jpg)
1
Florida LAKEWATCH Report for Johio in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 202: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/202.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 5 - 10 7 (22)
Total Nitrogen (µg/L) 393 - 745 556 (22)
Chlorophyll- uncorrected (µg/L) 2 - 4 2 (22)
Secchi (ft) 7.0 - 19.6 12.7 (22)
Secchi (m) 2.1 - 6.0 3.9 (22)
Color (Pt-Co Units) 6 - 15 9 (19)
Specific Conductance (µS/cm@25 C) 149 - 280 219 (13)
Lake Classification Clear Hardwater
![Page 203: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/203.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Johio
GNIS Number 284833
Latitude 28.5773
Longitude -81.5104
Water Body Type Lake
Surface Area (ha and acre) 11 ha or 27.2 acre
Period of Record (year) 1997 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 7 (5 to 10)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 556 (393 to 745)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 204: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/204.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 205: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/205.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 206: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/206.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 207: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/207.jpg)
1
Florida LAKEWATCH Report for John's in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 208: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/208.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 14 - 76 35 (30)
Total Nitrogen (µg/L) 735 - 1400 971 (30)
Chlorophyll- uncorrected (µg/L) 3 - 24 11 (30)
Secchi (ft) 1.6 - 6.9 4.2 (30)
Secchi (m) 0.5 - 2.1 1.3 (30)
Color (Pt-Co Units) 46 - 149 70 (17)
Specific Conductance (µS/cm@25 C) 169 - 213 187 (13)
Lake Classification Colored
![Page 209: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/209.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name John's
GNIS Number 284856
Latitude 28.5415
Longitude -81.6324
Water Body Type Lake
Surface Area (ha and acre) 1563 ha or 3862.2 acre
Period of Record (year) 1989 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 35 (14 to 76)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 971 (735 to 1400)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 210: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/210.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 211: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/211.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 212: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/212.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 213: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/213.jpg)
1
Florida LAKEWATCH Report for La Grange in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 214: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/214.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 14 - 40 23 (7)
Total Nitrogen (µg/L) 427 - 1051 660 (7)
Chlorophyll- uncorrected (µg/L) 3 - 17 9 (7)
Secchi (ft) 3.8 - 11.1 6.5 (7)
Secchi (m) 1.1 - 3.4 2.0 (7)
Color (Pt-Co Units) 16 - 16 16 (1)
Specific Conductance (µS/cm@25 C) 157 - 157 157 (1)
Lake Classification Clear Hardwater
![Page 215: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/215.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name La Grange
GNIS Number 285590
Latitude 28.5076
Longitude -81.3438
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1991 to 2018
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 23 (14 to 40)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 660 (427 to 1051)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 216: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/216.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 217: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/217.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 218: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/218.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 219: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/219.jpg)
1
Florida LAKEWATCH Report for Lee in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 220: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/220.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 11 - 12 11 (5)
Total Nitrogen (µg/L) 400 - 474 427 (5)
Chlorophyll- uncorrected (µg/L) 3 - 4 3 (5)
Secchi (ft) 7.5 - 9.1 8.4 (5)
Secchi (m) 2.3 - 2.8 2.6 (5)
Color (Pt-Co Units) 25 - 34 28 (5)
Specific Conductance (µS/cm@25 C) 115 - 145 128 (5)
Lake Classification Clear Hardwater
![Page 221: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/221.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Lee
GNIS Number 285438
Latitude 28.59
Longitude -81.2069
Water Body Type Lake
Surface Area (ha and acre) 4.1 ha or 10.1 acre
Period of Record (year) 2015 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 11 (11 to 12)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 427 (400 to 474)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 222: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/222.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 223: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/223.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 224: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/224.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 225: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/225.jpg)
1
Florida LAKEWATCH Report for Little Conway in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 226: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/226.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 8 - 14 11 (23)
Total Nitrogen (µg/L) 377 - 536 460 (23)
Chlorophyll- uncorrected (µg/L) 2 - 9 3 (23)
Secchi (ft) 9.6 - 19.4 13.5 (22)
Secchi (m) 2.9 - 5.9 4.1 (22)
Color (Pt-Co Units) 5 - 9 7 (13)
Specific Conductance (µS/cm@25 C) 193 - 237 225 (8)
Lake Classification Clear Hardwater
![Page 227: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/227.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Little Conway
GNIS Number 285726
Latitude 28.481
Longitude -81.3633
Water Body Type Lake
Surface Area (ha and acre) 370 ha or 914.3 acre
Period of Record (year) 1995 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 11 (8 to 14)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 460 (377 to 536)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 228: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/228.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 229: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/229.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 230: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/230.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 231: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/231.jpg)
1
Florida LAKEWATCH Report for Little Down in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 232: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/232.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 14 - 18 17 (3)
Total Nitrogen (µg/L) 458 - 619 539 (3)
Chlorophyll- uncorrected (µg/L) 2 - 14 6 (3)
Secchi (ft) 6.0 - 9.7 7.5 (3)
Secchi (m) 1.8 - 3.0 2.3 (3)
Color (Pt-Co Units) 22 - 37 28 (2)
Specific Conductance (µS/cm@25 C) 261 - 281 271 (2)
Lake Classification Clear Hardwater
![Page 233: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/233.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Little Down
GNIS Number 281739
Latitude 28.5083
Longitude -81.5389
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1994 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 17 (14 to 18)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 539 (458 to 619)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 234: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/234.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 235: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/235.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 236: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/236.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 237: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/237.jpg)
1
Florida LAKEWATCH Report for Little Hickorynut in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 238: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/238.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 6 - 19 11 (26)
Total Nitrogen (µg/L) 510 - 1106 736 (26)
Chlorophyll- uncorrected (µg/L) 1 - 13 4 (26)
Secchi (ft) 4.1 - 14.8 9.1 (26)
Secchi (m) 1.2 - 4.5 2.8 (26)
Color (Pt-Co Units) 17 - 129 30 (16)
Specific Conductance (µS/cm@25 C) 120 - 166 140 (11)
Lake Classification Clear Hardwater
![Page 239: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/239.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Little Hickorynut
GNIS Number 283971
Latitude 28.4326
Longitude -81.649
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 11 (6 to 19)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 736 (510 to 1106)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 240: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/240.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 241: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/241.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 242: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/242.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 243: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/243.jpg)
1
Florida LAKEWATCH Report for Louise in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 244: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/244.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 11 - 17 13 (10)
Total Nitrogen (µg/L) 517 - 613 568 (10)
Chlorophyll- uncorrected (µg/L) 3 - 9 6 (10)
Secchi (ft) 5.4 - 12.8 9.6 (10)
Secchi (m) 1.6 - 3.9 2.9 (10)
Color (Pt-Co Units) 16 - 21 18 (2)
Specific Conductance (µS/cm@25 C) 239 - 267 253 (2)
Lake Classification Clear Hardwater
![Page 245: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/245.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Louise
GNIS Number 286141
Latitude 28.4775
Longitude -81.531
Water Body Type Lake
Surface Area (ha and acre) 59 ha or 145.8 acre
Period of Record (year) 1993 to 2018
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 13 (11 to 17)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 568 (517 to 613)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 246: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/246.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 247: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/247.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 248: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/248.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 249: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/249.jpg)
1
Florida LAKEWATCH Report for Lucy in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 250: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/250.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 18 - 75 32 (11)
Total Nitrogen (µg/L) 748 - 2178 1036 (11)
Chlorophyll- uncorrected (µg/L) 6 - 71 16 (11)
Secchi (ft) 2.0 - 5.5 3.6 (10)
Secchi (m) 0.6 - 1.7 1.1 (10)
Color (Pt-Co Units) 56 - 133 69 (6)
Specific Conductance (µS/cm@25 C) 114 - 121 117 (2)
Lake Classification Colored
![Page 251: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/251.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Lucy
GNIS Number 286204
Latitude 28.5721
Longitude -81.4952
Water Body Type Lake
Surface Area (ha and acre) 29 ha or 71.7 acre
Period of Record (year) 1989 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 32 (18 to 75)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1036 (748 to 2178)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 252: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/252.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 253: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/253.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 254: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/254.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 255: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/255.jpg)
1
Florida LAKEWATCH Report for Lurna in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 256: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/256.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 30 - 100 52 (26)
Total Nitrogen (µg/L) 452 - 1142 653 (26)
Chlorophyll- uncorrected (µg/L) 11 - 58 24 (26)
Secchi (ft) 2.5 - 6.7 4.3 (26)
Secchi (m) 0.7 - 2.0 1.3 (26)
Color (Pt-Co Units) 12 - 18 15 (17)
Specific Conductance (µS/cm@25 C) 157 - 186 165 (12)
Lake Classification Clear Hardwater
![Page 257: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/257.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Lurna
GNIS Number 286221
Latitude 28.5231
Longitude -81.3744
Water Body Type Lake
Surface Area (ha and acre) 3 ha or 7.4 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 52 (30 to 100)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 653 (452 to 1142)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 258: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/258.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 259: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/259.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 260: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/260.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 261: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/261.jpg)
1
Florida LAKEWATCH Report for Margaret in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 262: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/262.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 25 - 34 29 (3)
Total Nitrogen (µg/L) 684 - 1085 817 (3)
Chlorophyll- uncorrected (µg/L) 9 - 35 16 (3)
Secchi (ft) 2.8 - 5.3 3.9 (3)
Secchi (m) 0.9 - 1.6 1.2 (3)
Color (Pt-Co Units) 11 - 19 16 (3)
Specific Conductance (µS/cm@25 C) 236 - 239 237 (2)
Lake Classification Clear Hardwater
![Page 263: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/263.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Margaret
GNIS Number 286412
Latitude 28.5023
Longitude -81.3464
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 2001 to 2018
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 29 (25 to 34)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 817 (684 to 1085)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 264: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/264.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 265: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/265.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 266: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/266.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 267: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/267.jpg)
1
Florida LAKEWATCH Report for Moxie in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 268: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/268.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 20 11 (28)
Total Nitrogen (µg/L) 365 - 793 548 (28)
Chlorophyll- uncorrected (µg/L) 1 - 13 4 (28)
Secchi (ft) 4.4 - 13.6 7.7 (28)
Secchi (m) 1.3 - 4.1 2.4 (28)
Color (Pt-Co Units) 6 - 27 13 (19)
Specific Conductance (µS/cm@25 C) 93 - 125 110 (13)
Lake Classification Clear Hardwater
![Page 269: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/269.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Moxie
GNIS Number
Latitude 28.5818
Longitude -81.5348
Water Body Type Lake
Surface Area (ha and acre) 5 ha or 12.4 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 11 (7 to 20)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 548 (365 to 793)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 270: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/270.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 271: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/271.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 272: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/272.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 273: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/273.jpg)
1
Florida LAKEWATCH Report for North Lotta in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 274: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/274.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 27 - 100 49 (27)
Total Nitrogen (µg/L) 490 - 1298 893 (27)
Chlorophyll- uncorrected (µg/L) 10 - 44 24 (27)
Secchi (ft) 2.0 - 5.0 3.2 (27)
Secchi (m) 0.6 - 1.5 1.0 (27)
Color (Pt-Co Units) 10 - 59 39 (18)
Specific Conductance (µS/cm@25 C) 96 - 195 149 (12)
Lake Classification Clear Hardwater
![Page 275: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/275.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name North Lotta
GNIS Number 286126
Latitude 28.5527
Longitude -81.5098
Water Body Type Lake
Surface Area (ha and acre) 14 ha or 34.6 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 49 (27 to 100)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 893 (490 to 1298)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 276: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/276.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 277: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/277.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 278: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/278.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 279: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/279.jpg)
1
Florida LAKEWATCH Report for Ola in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 280: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/280.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 9 - 14 12 (30)
Total Nitrogen (µg/L) 505 - 761 610 (30)
Chlorophyll- uncorrected (µg/L) 2 - 6 4 (30)
Secchi (ft) 9.9 - 16.1 12.8 (30)
Secchi (m) 3.0 - 4.9 3.9 (30)
Color (Pt-Co Units) 7 - 12 9 (19)
Specific Conductance (µS/cm@25 C) 216 - 267 243 (13)
Lake Classification Clear Hardwater
![Page 281: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/281.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Ola
GNIS Number 288075
Latitude 28.7553
Longitude -81.625
Water Body Type Lake
Surface Area (ha and acre) 180 ha or 444.8 acre
Period of Record (year) 1990 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 12 (9 to 14)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 610 (505 to 761)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 282: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/282.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 283: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/283.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 284: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/284.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 285: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/285.jpg)
1
Florida LAKEWATCH Report for Olivia in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 286: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/286.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 17 - 89 40 (14)
Total Nitrogen (µg/L) 653 - 1277 909 (14)
Chlorophyll- uncorrected (µg/L) 9 - 72 27 (14)
Secchi (ft) 2.4 - 7.1 4.3 (14)
Secchi (m) 0.7 - 2.1 1.3 (14)
Color (Pt-Co Units) 14 - 23 18 (4)
Specific Conductance (µS/cm@25 C) 221 - 221 221 (1)
Lake Classification Clear Hardwater
![Page 287: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/287.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Olivia
GNIS Number 288150
Latitude 28.5247
Longitude -81.5201
Water Body Type Lake
Surface Area (ha and acre) 35 ha or 86.5 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 40 (17 to 89)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 909 (653 to 1277)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 288: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/288.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 289: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/289.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 290: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/290.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 291: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/291.jpg)
1
Florida LAKEWATCH Report for Olympia in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 292: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/292.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 8 - 21 11 (28)
Total Nitrogen (µg/L) 452 - 889 598 (28)
Chlorophyll- uncorrected (µg/L) 3 - 12 5 (28)
Secchi (ft) 4.6 - 12.5 8.4 (28)
Secchi (m) 1.4 - 3.8 2.6 (28)
Color (Pt-Co Units) 6 - 24 11 (19)
Specific Conductance (µS/cm@25 C) 142 - 228 189 (13)
Lake Classification Clear Hardwater
![Page 293: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/293.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Olympia
GNIS Number 288155
Latitude 28.5649
Longitude -81.5231
Water Body Type Lake
Surface Area (ha and acre) 62 ha or 153.2 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 11 (8 to 21)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 598 (452 to 889)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 294: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/294.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 295: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/295.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 296: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/296.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 297: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/297.jpg)
1
Florida LAKEWATCH Report for Peach in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 298: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/298.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 13 - 37 19 (28)
Total Nitrogen (µg/L) 401 - 1225 715 (28)
Chlorophyll- uncorrected (µg/L) 2 - 29 9 (28)
Secchi (ft) 3.0 - 12.3 6.0 (28)
Secchi (m) 0.9 - 3.8 1.8 (28)
Color (Pt-Co Units) 11 - 31 18 (19)
Specific Conductance (µS/cm@25 C) 92 - 148 114 (13)
Lake Classification Clear Hardwater
![Page 299: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/299.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Peach
GNIS Number 288615
Latitude 28.5845
Longitude -81.5308
Water Body Type Lake
Surface Area (ha and acre) 3 ha or 7.4 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 19 (13 to 37)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 715 (401 to 1225)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 300: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/300.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 301: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/301.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 302: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/302.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 303: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/303.jpg)
1
Florida LAKEWATCH Report for Prairie in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 304: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/304.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 19 - 85 29 (20)
Total Nitrogen (µg/L) 781 - 1899 1064 (20)
Chlorophyll- uncorrected (µg/L) 6 - 34 14 (20)
Secchi (ft) 1.4 - 5.2 3.5 (20)
Secchi (m) 0.4 - 1.6 1.1 (20)
Color (Pt-Co Units) 20 - 71 43 (16)
Specific Conductance (µS/cm@25 C) 106 - 159 124 (13)
Lake Classification Colored
![Page 305: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/305.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Prairie
GNIS Number 289284
Latitude 28.5968
Longitude -81.5103
Water Body Type Lake
Surface Area (ha and acre) 15 ha or 37.1 acre
Period of Record (year) 1997 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 29 (19 to 85)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1064 (781 to 1899)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 306: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/306.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 307: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/307.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 308: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/308.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 309: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/309.jpg)
1
Florida LAKEWATCH Report for Primavista in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 310: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/310.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 23 - 43 30 (28)
Total Nitrogen (µg/L) 789 - 2230 1271 (28)
Chlorophyll- uncorrected (µg/L) 16 - 40 25 (28)
Secchi (ft) 1.7 - 4.6 2.8 (28)
Secchi (m) 0.5 - 1.4 0.8 (28)
Color (Pt-Co Units) 13 - 24 17 (19)
Specific Conductance (µS/cm@25 C) 203 - 283 248 (13)
Lake Classification Clear Hardwater
![Page 311: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/311.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Primavista
GNIS Number 291635
Latitude 28.5635
Longitude -81.5352
Water Body Type Lake
Surface Area (ha and acre) 12 ha or 29.7 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 30 (23 to 43)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1271 (789 to 2230)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 312: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/312.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 313: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/313.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 314: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/314.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 315: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/315.jpg)
1
Florida LAKEWATCH Report for Serene in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 316: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/316.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 11 - 11 11 (1)
Total Nitrogen (µg/L) 438 - 438 438 (1)
Chlorophyll- uncorrected (µg/L) 4 - 4 4 (1)
Secchi (ft) 11.5 - 11.5 11.5 (1)
Secchi (m) 3.5 - 3.5 3.5 (1)
Color (Pt-Co Units) - (0)
Specific Conductance (µS/cm@25 C) - (0)
Lake Classification
![Page 317: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/317.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Serene
GNIS Number 2764905
Latitude 28.4407
Longitude -81.5012
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 2018 to 2018
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 11 (11 to 11)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 438 (438 to 438)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 318: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/318.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 319: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/319.jpg)
1
Florida LAKEWATCH Report for Sheen in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 320: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/320.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 11 9 (8)
Total Nitrogen (µg/L) 368 - 473 417 (8)
Chlorophyll- uncorrected (µg/L) 1 - 3 2 (9)
Secchi (ft) 8.0 - 12.4 10.5 (9)
Secchi (m) 2.4 - 3.8 3.2 (9)
Color (Pt-Co Units) 16 - 16 16 (1)
Specific Conductance (µS/cm@25 C) 244 - 244 244 (1)
Lake Classification Clear Hardwater
![Page 321: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/321.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Sheen
GNIS Number 290953
Latitude 28.4361
Longitude -81.5144
Water Body Type Lake
Surface Area (ha and acre) 229 ha or 565.9 acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 9 (7 to 11)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 417 (368 to 473)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 322: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/322.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 323: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/323.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 324: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/324.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 325: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/325.jpg)
1
Florida LAKEWATCH Report for South Lotta in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 326: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/326.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 19 - 177 51 (28)
Total Nitrogen (µg/L) 483 - 1307 881 (28)
Chlorophyll- uncorrected (µg/L) 10 - 49 23 (28)
Secchi (ft) 2.0 - 5.0 3.1 (28)
Secchi (m) 0.6 - 1.5 0.9 (28)
Color (Pt-Co Units) 38 - 65 50 (18)
Specific Conductance (µS/cm@25 C) 125 - 195 152 (12)
Lake Classification Colored
![Page 327: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/327.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name South Lotta
GNIS Number 286126
Latitude 28.5504
Longitude -81.5132
Water Body Type Lake
Surface Area (ha and acre) 13 ha or 32.1 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 51 (19 to 177)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 881 (483 to 1307)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 328: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/328.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 329: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/329.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 330: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/330.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 331: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/331.jpg)
1
Florida LAKEWATCH Report for Spring 2 in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 332: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/332.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 15 9 (28)
Total Nitrogen (µg/L) 454 - 801 556 (28)
Chlorophyll- uncorrected (µg/L) 1 - 13 4 (28)
Secchi (ft) 5.9 - 18.2 9.7 (28)
Secchi (m) 1.8 - 5.5 3.0 (28)
Color (Pt-Co Units) 8 - 50 21 (19)
Specific Conductance (µS/cm@25 C) 179 - 261 220 (13)
Lake Classification Clear Hardwater
![Page 333: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/333.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Spring 2
GNIS Number 291550
Latitude 28.5815
Longitude -81.5216
Water Body Type Lake
Surface Area (ha and acre) 24 ha or 59.3 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 9 (7 to 15)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 556 (454 to 801)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 334: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/334.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 335: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/335.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 336: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/336.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 337: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/337.jpg)
1
Florida LAKEWATCH Report for Starke in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 338: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/338.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 17 - 34 24 (28)
Total Nitrogen (µg/L) 669 - 1550 1020 (28)
Chlorophyll- uncorrected (µg/L) 10 - 34 21 (28)
Secchi (ft) 2.0 - 5.2 3.0 (28)
Secchi (m) 0.6 - 1.6 0.9 (28)
Color (Pt-Co Units) 12 - 23 16 (19)
Specific Conductance (µS/cm@25 C) 208 - 259 241 (13)
Lake Classification Clear Hardwater
![Page 339: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/339.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Starke
GNIS Number 291635
Latitude 28.5722
Longitude -81.5332
Water Body Type Lake
Surface Area (ha and acre) 133 ha or 328.6 acre
Period of Record (year) 1992 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 24 (17 to 34)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1020 (669 to 1550)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 340: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/340.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 341: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/341.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 342: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/342.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 343: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/343.jpg)
1
Florida LAKEWATCH Report for Susannah in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 344: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/344.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 11 - 31 20 (29)
Total Nitrogen (µg/L) 424 - 1142 617 (29)
Chlorophyll- uncorrected (µg/L) 3 - 35 8 (29)
Secchi (ft) 3.1 - 12.1 7.5 (29)
Secchi (m) 0.9 - 3.7 2.3 (29)
Color (Pt-Co Units) 9 - 31 17 (19)
Specific Conductance (µS/cm@25 C) 160 - 273 192 (13)
Lake Classification Clear Hardwater
![Page 345: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/345.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Susannah
GNIS Number 291902
Latitude 28.5639
Longitude -81.3234
Water Body Type Lake
Surface Area (ha and acre) 31 ha or 76.6 acre
Period of Record (year) 1990 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 20 (11 to 31)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 617 (424 to 1142)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 346: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/346.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 347: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/347.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 348: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/348.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 349: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/349.jpg)
1
Florida LAKEWATCH Report for Underhill in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 350: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/350.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 12 - 37 23 (5)
Total Nitrogen (µg/L) 317 - 946 625 (5)
Chlorophyll- uncorrected (µg/L) 4 - 48 18 (5)
Secchi (ft) 2.6 - 9.4 4.5 (5)
Secchi (m) 0.8 - 2.9 1.4 (5)
Color (Pt-Co Units) 7 - 7 7 (1)
Specific Conductance (µS/cm@25 C) 84 - 84 84 (1)
Lake Classification Clear Softwater
![Page 351: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/351.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Underhill
GNIS Number 292644
Latitude 28.5413
Longitude -81.3347
Water Body Type Lake
Surface Area (ha and acre) 59 ha or 145.8 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 23 (12 to 37)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 625 (317 to 946)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 352: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/352.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 353: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/353.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 354: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/354.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 355: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/355.jpg)
1
Florida LAKEWATCH Report for Virginia in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 356: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/356.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 15 - 17 16 (4)
Total Nitrogen (µg/L) 500 - 686 553 (4)
Chlorophyll- uncorrected (µg/L) 7 - 15 10 (4)
Secchi (ft) 5.2 - 6.5 5.8 (4)
Secchi (m) 1.6 - 2.0 1.8 (4)
Color (Pt-Co Units) 10 - 36 16 (4)
Specific Conductance (µS/cm@25 C) 175 - 191 184 (4)
Lake Classification Clear Hardwater
![Page 357: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/357.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Virginia
GNIS Number 292785
Latitude 28.5919
Longitude -81.3438
Water Body Type Lake
Surface Area (ha and acre) 90 ha or 222.4 acre
Period of Record (year) 2016 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 16 (15 to 17)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 553 (500 to 686)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 358: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/358.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 359: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/359.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 360: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/360.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 361: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/361.jpg)
1
Florida LAKEWATCH Report for Waumpi in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 362: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/362.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 32 - 102 59 (22)
Total Nitrogen (µg/L) 660 - 1564 972 (22)
Chlorophyll- uncorrected (µg/L) 8 - 65 24 (22)
Secchi (ft) 1.4 - 2.7 2.0 (21)
Secchi (m) 0.4 - 0.8 0.6 (21)
Color (Pt-Co Units) 24 - 85 44 (19)
Specific Conductance (µS/cm@25 C) 181 - 248 211 (13)
Lake Classification Colored
![Page 363: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/363.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Waumpi
GNIS Number
Latitude 28.6314
Longitude -81.3293
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1998 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 59 (32 to 102)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 972 (660 to 1564)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 364: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/364.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 365: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/365.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 366: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/366.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 367: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/367.jpg)
1
Florida LAKEWATCH Report for Waunatta in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 368: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/368.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 13 - 30 17 (27)
Total Nitrogen (µg/L) 317 - 918 566 (27)
Chlorophyll- uncorrected (µg/L) 1 - 25 7 (27)
Secchi (ft) 3.8 - 10.1 6.8 (26)
Secchi (m) 1.1 - 3.1 2.1 (26)
Color (Pt-Co Units) 14 - 39 21 (17)
Specific Conductance (µS/cm@25 C) 93 - 160 130 (12)
Lake Classification Clear Hardwater
![Page 369: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/369.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Waunatta
GNIS Number 292951
Latitude 28.6016
Longitude -81.2776
Water Body Type Lake
Surface Area (ha and acre) 28 ha or 69.2 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 17 (13 to 30)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 566 (317 to 918)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 370: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/370.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 371: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/371.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 372: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/372.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 373: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/373.jpg)
1
Florida LAKEWATCH Report for Wauseon Bay in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 374: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/374.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 9 - 20 12 (4)
Total Nitrogen (µg/L) 424 - 528 492 (4)
Chlorophyll- uncorrected (µg/L) 2 - 5 3 (4)
Secchi (ft) 9.2 - 15.3 11.7 (4)
Secchi (m) 2.8 - 4.7 3.6 (4)
Color (Pt-Co Units) 11 - 13 12 (2)
Specific Conductance (µS/cm@25 C) 262 - 267 265 (2)
Lake Classification Clear Hardwater
![Page 375: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/375.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Wauseon Bay
GNIS Number 279743
Latitude 28.5037
Longitude -81.5446
Water Body Type Lake
Surface Area (ha and acre) ha or acre
Period of Record (year) 1993 to 2019
Lake Trophic Status (CHL) Mesotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 12 (9 to 20)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 492 (424 to 528)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 376: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/376.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 377: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/377.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 378: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/378.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 379: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/379.jpg)
1
Florida LAKEWATCH Report for Weldona in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 380: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/380.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 53 - 147 78 (18)
Total Nitrogen (µg/L) 780 - 1907 1190 (18)
Chlorophyll- uncorrected (µg/L) 31 - 105 56 (18)
Secchi (ft) 1.3 - 3.4 2.1 (18)
Secchi (m) 0.4 - 1.0 0.6 (18)
Color (Pt-Co Units) 21 - 31 24 (17)
Specific Conductance (µS/cm@25 C) 142 - 188 167 (13)
Lake Classification Clear Hardwater
![Page 381: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/381.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Weldona
GNIS Number 293016
Latitude 28.5303
Longitude -81.36
Water Body Type Lake
Surface Area (ha and acre) 5 ha or 12.4 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Hypereutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 78 (53 to 147)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 1190 (780 to 1907)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 382: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/382.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 383: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/383.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 384: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/384.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 385: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/385.jpg)
1
Florida LAKEWATCH Report for Willis in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 386: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/386.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 7 - 14 10 (29)
Total Nitrogen (µg/L) 427 - 610 506 (29)
Chlorophyll- uncorrected (µg/L) 1 - 6 3 (29)
Secchi (ft) 6.9 - 15.2 10.7 (29)
Secchi (m) 2.1 - 4.6 3.3 (29)
Color (Pt-Co Units) 9 - 24 15 (15)
Specific Conductance (µS/cm@25 C) 150 - 178 168 (9)
Lake Classification Clear Hardwater
![Page 387: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/387.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Willis
GNIS Number 293349
Latitude 28.3959
Longitude -81.4766
Water Body Type Lake
Surface Area (ha and acre) 58 ha or 143.3 acre
Period of Record (year) 1989 to 2018
Lake Trophic Status (CHL) Oligotrophic
TP Zone TP3
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 10 (7 to 14)
TN Zone TN3
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 506 (427 to 610)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 388: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/388.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 389: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/389.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 390: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/390.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.
![Page 391: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/391.jpg)
1
Florida LAKEWATCH Report for Winyah in Orange County
Using Data Downloaded 1/17/2020
Introduction for Lakes
This report summarizes data collected on systems that have been part of the LAKEWATCH program. Data
are from the period of record for individual systems. Part one allows the comparison of data with Florida
Department of Environmental Protection’s Numeric Nutrient Criteria. Part two allows a comparison of the
long-term mean nutrient concentrations with nutrient zone concentrations published by LAKEWATCH staff
(Bachmann et al. 2012; https://lakewatch.ifas.ufl.edu/resources/bibliography/). Finally, this report examines
data for long-term trends that may be occurring in individual systems but only for systems with five or more
years of data. Step by step instructions on how to use the data tables are provided on page 4 of this report.
Florida Department of Environmental Protection (FDEP) Nutrient Criteria for Lakes (Table 1)
For lakes, the numeric interpretations of the nutrient criterion in paragraph 62-302.530(47)(b), F.A.C., based
on chlorophyll a are shown in the Table 1. The applicable interpretations for TN and TP will vary on an
annual basis, depending on the availability and concentration of chlorophyll a data for the lake. The numeric
interpretations for TN, TP, and chlorophyll shall not be exceeded more than once in any consecutive three
year period.
a. If annual geometric mean chlorophyll a does not exceed the chlorophyll value for the lake classification in
the table below, then the TN and TP numeric interpretations for that calendar year shall be the annual
geometric means of the maximum calculated numeric interpretation in Table 1.
b. If there are insufficient data to calculate the annual geometric mean chlorophyll for a given year or the
annual geometric mean chlorophyll exceeds the values in the Table 1 for the correct lake classification, then
the applicable numeric interpretations for TN and TP shall be the minimum values in the Table 1.
Long-Term Data Summary for Lakes (Table 2): Definitions
• Total Phosphorus (µg/L): The nutrient most often limiting growth of plant/algae.
• Total Nitrogen (µg/L): Another nutrient needed for aquatic plant/algae growth but only limiting
when nitrogen to phosphorus ratios are generally less than 10.
• Chlorophyll-uncorrected (µg/L): Chlorophyll concentrations are used to measure relative
abundances of open water algal population.
• Secchi (ft), Secchi (m): Secchi measurements are estimates of water clarity.
• Color (Pt-Co Units): LAKEWATCH measures true color, which is the color of the water after
particles have been filtered out.
• Specific Conductance (µS/cm@25°C): Measurement of the ability of water to conduct electricity
and can be used to estimate the amount of dissolved materials in water.
• Lake Classification: The new numeric nutrient criteria for Florida require that lakes must first be
classified into one of three group based on color and alkalinity or specific conductance; colored lakes
(color greater than 40 Pt-Co units), clear soft water lakes (color less than or equal to 40 Pt-Co units
and alkalinity less than or equal to 20 mg/L as CaCO3 or specific conductance less than or equal to
100 µs/cm @25 C), and clear hard water lakes (color less than 40 Pt-Co units and alkalinity greater
than 20 mg/L as CaCO3 or specific conductance greater 100 µS/cm @ 25 C).
![Page 392: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/392.jpg)
2
Table 1. Florida Department of Environmental Protection’s Numeric Nutrient Criteria for lakes.
Long Term Geometric
Mean Lake Color and Long-
Term Geometric Mean
Color, Alkalinity and
Specific Conductance
Annual
Geometric
Mean
Chlorophyll-
corrected
Minimum calculated
numeric interpretation
Maximum calculated
numeric interpretation
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
Annual
Geometric
Mean Total
Phosphorus
Annual
Geometric
Mean Total
Nitrogen
> 40 Platinum Cobalt Units
Colored Lakes
20 µg/L 50 µg/L 1270 µg/L 160 µg/L1 2230 µg/L
≤ 40 Platinum Cobalt Units
and > 20 mg/L CaCO3
or
>100 µS/cm@25 C
Clear Hard Water Lakes
20 µg/L
30 µg/L
1050 µg/L
90 µg/L
1910 µg/L
≤ 40 Platinum Cobalt Units
and ≤ 20 mg/L CaCO3
or
< 100 µS/cm@25 C
Clear Soft Water Lakes
6 µg/L
10 µg/L
51 µg/L
30 µg/L
930 µg/L
1 For lakes with color > 40 PCU in the West Central Nutrient Watershed Region, the maximum TP limit
shall be the 490 µg/L TP streams threshold for the region.
For the purpose of subparagraph 62-302.531(2)(b)1., F.A.C., color shall be assessed as true color and shall
be free from turbidity. Lake color and alkalinity shall be the long-term geometric mean, based on a minimum
of ten data points over at least three years with at least one data point in each year. If insufficient alkalinity
data are available, long-term geometric mean specific conductance values shall be used, with a value of <100
µS/cm@25 C used to estimate the mg/L CaCO3 alkalinity concentration until such time that alkalinity data
are available.
Table 2. Long-term trophic state data collected monthly by LAKEWATCH volunteers and
classification variables color and specific conductance (collected quarterly). Values in bold can be used
with Table 1 to evaluate compliance with nutrient criteria.
Parameter Minimum and Maximum
Annual Geometric Means
Grand Geometric Mean
(Sampling years)
Total Phosphorus (µg/L) 21 - 71 48 (17)
Total Nitrogen (µg/L) 367 - 941 721 (18)
Chlorophyll- uncorrected (µg/L) 9 - 63 30 (18)
Secchi (ft) 2.6 - 5.3 3.5 (18)
Secchi (m) 0.8 - 1.6 1.1 (18)
Color (Pt-Co Units) 14 - 36 20 (6)
Specific Conductance (µS/cm@25 C) 156 - 174 164 (3)
Lake Classification Clear Hardwater
![Page 393: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/393.jpg)
3
Base File Data for Lakes: Definitions and Nutrient Zone Maps
The long-term data summary will include the following parameters listed with a definition after each one:
• County: Name of county in which the lake resides.
• Name: Lake name that LAKEWATCH uses for the system.
• GNIS Number: Number created by USGS’s Geographic Names Information System.
• Latitude and Longitude: Coordinates identifying the exact location of station 1 for each system.
• Water Body Type: Four different types of systems; lakes, estuaries, river/streams and springs.
• Surface Area (ha and acre): LAKEWATCH lists the surface area of a lake if it is available.
• Mean Depth (m and ft): This mean depth is calculated from multiple depth finder transects across a
lake that LAKEWATCH uses for estimating plant abundances.
• Period of Record (year): Years a lake has been in the LAKEWATCH program.
• TP Zone and TN Zone: Nutrient zones defined by Bachmann et al (2012).
• Long-Term TP and TN Geometric Mean Concentration (µg/L: min and max): Grand Geometric
Means of all annual geometric means (µg/L) with minimum and maximum annual geometric means.
• Lake Trophic Status (CHL): Tropic state classification using the long-term chlorophyll average.
Table 3. Base File Data, long-term nutrient grand geometric means and Nutrient Zone classification
listing the 90th percentile concentrations in Figure 1. Values in bold can be used for Nutrient Zone
comparisons.
County Orange
Name Winyah
GNIS Number 293432
Latitude 28.5791
Longitude -81.3689
Water Body Type Lake
Surface Area (ha and acre) 7 ha or 17.3 acre
Period of Record (year) 1991 to 2019
Lake Trophic Status (CHL) Eutrophic
TP Zone TP4
Grand TP Geometric Mean Concentration (µg/L, min. and max.) 48 (21 to 71)
TN Zone TN4
Grand TN Geometric Mean Concentration (µg/L, min. and max.) 721 (367 to 941)
Figure 1. Maps showing Florida phosphorus and nitrogen zones and the nutrient concentrations of the
upper 90% of lakes within each zone (Bachmann et al. 2012). Explanation on how to interpret the
Nutrient Zones on page 4, below.
![Page 394: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/394.jpg)
4
Interpreting FDEP’s Numeric Nutrient Criteria (NNC): These are instructions for using Table 1 and 2
to determine impairment status based on FDEP’s NNC.
1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no
classification is listed then there is not enough data available to classify your lake).
a. The Lake Classification tells you which row to use in Table 1.
2. Identify your waterbody’s Grand Geometric Mean Chlorophyll-uncorrected in Table 2.
a. Compare this number to the Annual Geometric Mean Chlorophyll-corrected (2nd column) in Table 1.
b. If your lake’s Chlorophyll-uncorrected concentration is greater than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Minimum calculated numeric interpretation columns.
c. If your lake’s Chlorophyll-uncorrected concentration is less than the Annual Geometric Mean
Chlorophyll-corrected concentration use the Maximum calculated numeric interpretation columns.
3. Identify your lake’s Total Phosphorus and Total Nitrogen Grand Geometric Mean concentration in Table 2
and compare them to the appropriate Annual Geometric Mean Total Phosphorus and Annual Geometric Mean
Total Nitrogen values in Table 1.
4. If your lake’s concentrations from Table 2 are greater than FDEP’s NNC values from Table 1, your lake may
be considered impaired. If they are below, it may be considered unimpaired.
Nutrient Zones and “Natural Background”
Administrative code definitions 62-302.200 (19): “Natural background” shall mean the condition of waters in the
absence of man-induced alterations based on the best scientific information available to the Department. The
establishment of natural background for an altered waterbody may be based upon a similar unaltered waterbody,
historical pre-alteration data, paleolimnological examination of sediment cores, or examination of geology and soils.
When determining natural background conditions for a lake, the lake’s location and regional characteristics as
described and depicted in the U.S. Environmental Protection Agency document titled Lake Regions of Florida
(EPA/R-97/127, dated 1997, U.S. Environmental Protection Agency, National Health and Environmental Effects
Research Laboratory, Corvallis, OR) (http://www.flrules.org/Gateway/reference.asp?No=Ref-06267), which is
incorporated by reference herein, shall also be considered. The lake regions in this document are grouped Nutrient
Zones according to ambient total phosphorus and total nitrogen concentrations listed in Table 1 found in Bachmann, R.
W., Bigham D. L., Hoyer M. V., Canfield D. E, Jr. 2012. A strategy for establishing numeric nutrient criteria for
Florida lakes. Lake Reservoir Management. 28:84-92.
Interpreting Florida LAKEWATCH’s Nutrient Zones: These are instructions for using Table 3 and
Figure 1 to determine nutrient status based on Nutrient Zones.
1. Identify your lake’s TP Zone in Table 3.
a. Locate this TP Zone (left map) and its corresponding nutrient concentration in Figure 1.
2. Locate your lake’s Long-Term Grand Geometric Mean TP Concentration value in Table 3.
3. Compare your lake’s Long-Term Grand Geometric Mean TP Concentration from Table 3 to the appropriate
TP Zone nutrient concentration from Figure 1.
a. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is higher than the TP
zone nutrient concentration, your lake’s nutrient concentration is above “Natural Background”.
b. If your lake’s Long-Term Grand Geometric Mean TP Concentration number is lower than the TP zone
nutrient concentration, your lake’s nutrient concentration is within “Natural Background”.
4. Repeat these same steps with the TN Zone and Long-term Grand Geometric Mean TN Concentration
![Page 395: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/395.jpg)
5
Figure 1 and Figure 2. Trend plots of annual average total phosphorus and annual average total
nitrogen versus year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0;
higher the R2 the stronger the relation) and the p value indicates if the relation is significant (p < 0.05
is significant). Trend Status are reported on plots.
![Page 396: Florida LAKEWATCH Report for Apopka in Orange County Using ... · 1. Identify your lake’s Lake Classification in Table 2 (Colored, Clear Hard Water, or Clear Soft Water) (if no](https://reader035.vdocuments.mx/reader035/viewer/2022081617/604f0846d04f1a13936b2a54/html5/thumbnails/396.jpg)
6
Figure 3 and Figure 4. Trend plots of annual average chlorophyll and annual average Secchi versus
year. The R2 value indicates the strength of the relations (ranges from 0.0 to 1.0; higher the R2 the
stronger the relations and the p value indicates if the relation is significant (p < 0.05 is significant).
Trend status are reported on plots.