reservoir and lake nutrient criteria
DESCRIPTION
Reservoir and Lake Nutrient Criteria. A Different Approach. D.V. Obrecht, J.R. Jones & M.K. Knowlton – MU Limnology. UMBRELLA APPROACH. 1) Reference reservoirs and lakes – 75 th percentile 2) All reservoirs and lakes – 25 th percentile 3) EPA’s 304(a) criteria. Oxbow lakes (n=12) - PowerPoint PPT PresentationTRANSCRIPT
Reservoir and Lake Nutrient Criteria
A Different ApproachA Different Approach
D.V. Obrecht, J.R. Jones & M.K. Knowlton – MU Limnology
UMBRELLA APPROACH
1) Reference reservoirs and lakes – 75th percentile
2) All reservoirs and lakes – 25th percentile
3) EPA’s 304(a) criteria
Oxbow lakes (n=12)
TP = 212 ug/L
TN = 1.56 mg/L
Reservoirs (n=135)
TP = 45 ug/L
TN = 0.73 mg/L
Reservoir TP (µg/L) range of geomeans
Maysville (n=10) 182 116 – 300
Grindstone (n=5) 147 90 - 218
Unionville (n=10) 98 68 - 155
Long Branch (n=20) 48 30 - 115
Viking (n=16) 26 19 - 40
Forest (n=19) 23 14 - 44
STEP APPROACH
Designated Use
Impairment of use
Algal biomass
Nutrient levels
Criteria level
Drinking Water Supply
Impairments
-taste and odor
-clogging of filters
-algal toxins
There may be too many factors that influence water quality and too much variability within and among systems to allow for the setting of a single set of criteria to be used by
the state for regulation.
EPA allows some flexibility:
…(states can) develop their own criteria which reflect more locally representative conditions.
…prioritize their waters…..Such an approach should include a mechanism for evaluating the sensitivity of all waters…considering current and expected land use…
EPA memorandum, Nov. 14, 2001
A Different Approach!
A lake is a reflection of its watershed.
0 5 20 40 60 80
100
200
5
10
5
r = 0.622
25
50
Cropland (%)
To
tal
Ph
osp
ho
rus
(µg
/L)
A reservoir is also a reflection of its watershed,
and the intensity of that reflection is dictated by
hydrology.
Regression model resultsEquation r2
TP = 4.27 + 0.36 %crop 0.62
TP = 5.53 + 0.33 %crop – 0.50DH 0.73
TP = 5.20 + 0.35crop% - 0.37 DH + 0.12 FI 0.77
DH is dam height, a surrogate from reservoir morphology
FI is flushing index
Volume 100
outflow 100
outflow 200
inflow 100
inflow 50
inflow 200
Volume / Inflow = Residence Time (years)
outflow 50
Volume 100
Volume 100
RT = 2 years
RT = 1 years
RT = .5 years
1 3 5 7 9
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
= TP < 20 g/L
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
= TP 20 - 50 g/L
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
= TP 50 - 75 g/L
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
= TP 75 - 100 g/L
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
= TP > 100 g/L
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
Proportion crop
Short Res. Time
Med. Res. Time
Long Res. Time
> 40%
20 – 40%
10 – 20%
1 – 10%
< 1%
Proportion crop
Short Res. Time
Med. Res. Time
Long Res. Time
> 40% 116 ug/L 75 ug/L 47ug/L
20 – 40% 97 ug/L 80 ug/L 53 ug/L
10 – 20% 59 ug/L 54 ug/L 33 ug/L
1 – 10% 40 ug/L 27 ug/L
< 1% 17 ug/L
Residence Time (months)
0
50
100
150
To
tal
Ph
osp
ho
rus
(ug
/L)
>12 6-12 <6
>40% 20% - 40% 10% - 20% 4% - 10% crop =
>10 >106-10 6-10<6 <6 <2>2
Can we use agriculture to classify reservoirs?
Can we use agriculture to classify reservoirs?
USGS photo
Reservoirs were built into landscapes that had already been altered.
No Restoration
Water quality in a reservoir is a function of morphology/hydrology and location within the landscape.
7,600 – 34,000 ac
34,000 – 58,000 ac
58,000 – 87,000 ac
87,000 – 169,000 ac
Harvested acres of corn, 1920
30 counties
26 counties
36 counties
22 countiesBetween 11% and 21% of total Missouri land surface dedicated to just corn production in 1920!
Missouri’s reservoirs >10 acres in sizeYear completed # %
1800-1920 122 8
1920-1940 267 18
1940-1960 68 5
1960-1980 909 61
1980-1995 121 8
0 1 2 3 4
Residence Time (years)
0.0
0.2
0.4
0.6
0.8
Cro
p L
and
Use
(p
rop
ort
ion
wat
ersh
ed)
Protect
Improvements possible
Limited potential
This approach allows the state to:
-Identify and protect the reservoirs that have low watershed impacts.
-Identify and focus efforts on the reservoirs that have higher nutrient concentration than expected, given watershed land use and hydrology.
-Gauge the potential for successful nutrient reduction by looking at the factors that control in-reservoir nutrient concentrations. And focus limited resources ($$) on those reservoirs where improvements can be made.