Nonpoint Source Pollution

Some basic principles Example study of total pollution loads in

the Corpus Christi Bay System– rainfall-runoff relationship– point and nonpoint source loads– connection to bay water quality

Adapt Water to the Land System

LandCharacterization

(Land use,Soils,

Climate,Terrain)

Water Characterization(water yield, flooding, groundwater, pollution, sediment)

Non Point Source Pollution(mean annual flowsand pollutant loads)

Land-WaterConnection

TransformCoefficient

Water yield Runoff coefficient, C

Flood runoff SCS Curve Number, CN

Groundwater Recharge rate (mm/yr)

Water quality Expected Mean Concentration(mg/l)

Sediment yield Erosion rate (tons/ha-yr)

Possible Land-Water Transform Coefficients

Water

Land

Expected Mean Concentration

EMC = Load Mass/Flow Volume either on a single event basis or as an annual average

Q C

T T

L

0 0 0T

T

dttQV0

)( T

dttLM0

)(EMC =M/V

Flow Concentration Load

L(t)=Q(t)*C(t)

Map-Based Surface Water Runoff

Runoff, Q (mm/yr)

Precipitation, P(mm/yr)

Accumulated Runoff (cfs)

P

Q

Runoff CoefficientC = Q/P

Water Quality: Pollution Loading Module

DEMPrecip. Runoff

LandUse

EMC Table

ConcentrationLoad

AccumulatedLoad

Load [Mass/Time] = Runoff [Vol/Time] x Concentration [Mass/Vol]

Expected Mean Concentration

Constituent Resident. Comm. Indust. Transp. Agric. Range UndevelTotal Nitrogen (mg/l) 1.82 1.34 1.26 1.86 4.40 0.70 1.50Total Phosphorus (mg/l) 0.57 0.32 0.28 0.22 1.30 <0.01 0.12Oil and Grease (mg/l) 1.7 9.0 3.0 0.4Copper (ug/l) 15.0 14.5 15.0 11.0 1.5 <10Chromium (ug/l) 2.1 10.0 7.0 3.0 <10 7.5Zinc (ug/l) 80 180 245 60 141 16 6

Land Use

EMC

Table derived from USGSwater quality monitoring sites

Total Constituent Loads

Input for WaterQuality Model

Water Quality: Land Surface -Water Body Connection

Bay Water Quality

Readings on Nonpoint Source Pollution(Handbook of Hydrology on reserve in Engr Library)

Handbook of Hydrology: Sec 14.1 and 14.2 on nonpoint source pollution sources

Handbook of Hydrology: Sec 28.6 on design for water quality enhancement

Master’s theses of – Christine Dartiguenave

http://www.crwr.utexas.edu/gis/gishyd98/library/dartig/rpt97_6.html – Ann Quenzer

http://www.crwr.utexas.edu/gis/gishyd98/library/quenzer/rpt98_1.html

– Patrice Melancon http://www.crwr.utexas.edu/crwr/reports/rpt99_3/rpt99_3.html

– Katherine Osborne http://www.crwr.utexas.edu/crwr/reports/rpt00_10/rpt00_10.htm

Total Loads and Water Quality in the Corpus Christi Bay System

Presented by: Ann Quenzer and Dr. David Maidment

Special Thanks:Corpus Christi Bay National Estuary ProgramFerdinand HellwegerDr. Nabil EidDr. George WardDr. Neal Armstrong

Purpose

To determine the rainfall/runoff relationship

To estimate the point and non-point source loads to the bay system

To quantify the relationship between the total loads and the bay system water quality

Basic Concept

Point and Non-pointEstimation

Total LoadsRouting

WaterQuality

Calculate Flowand Total Loads

Linkage of the Two Models

Steady-State Model

Purpose

To determine the rainfall/runoff relationship

Watershed Delineation

Sub-Watersheds

Precipitation

+ =

Precipitation Trendover Bay System

Merged Precipitation Files

Oregon State UniversityPrecipitation Data

Regression Inputs and OutputsWat er sh ed St r eamf l ow Pr ecip i t at i on %A g r i c %Ran g e

( mm/ y r ) ( mm/ y r )L os Omos 4. 07 618. 25 12. 24 87. 21Ch i l t i p i n 105. 80 841. 17 86. 40 10. 92San Fer n an d o 12. 36 661. 08 22. 09 76. 53San Dieg o 7. 65 664. 78 13. 29 85. 63Oso 112. 64 774. 75 96. 87 0. 97A r an sas 46. 03 809. 99 58. 07 37. 91Missi on 73. 51 846. 89 25. 22 73. 04Med io 29. 14 786. 75 40. 82 58. 30Cop an o 163. 90 927. 41 6. 56 66. 80

W ater

Q = 0

UrbanQ = 0.24 * P

where: Q = runoff depth (mm/yr)P = precipitation depth (mm/yr)

Q = 0.008312 * exp ( 0.011415 * P )

where: Q = runoff depth (mm/yr)P = precipitation depth (mm/yr)0.008312 = exp (-4.79004056)

Agriculture

Range Land, Barren, Forest Land, Other Q = 0.0053 * exp ( 0.010993 * P )

where: Q = runoff depth (m m/yr)P = precipitation depth (mm/yr)0.0053 = exp (-5.239702)

Surface Water RunoffPrecipitation vs. Runoff Curves

Chiltipin

Copano

Oso

Mission

AransasMedioSan Diego

Los OmosSan Fernando0.00

50.00

100.00

150.00

200.00

250.00

0 200 400 600 800 1000

Depth of Precipitation (mm/yr)

De

pth

of

Ex

pe

cte

d R

un

off

(m

m/y

r)

Range LandAgriculture

Urban

Stations

Land Use

+Precipitation

Surface Water RunoffPrecipitation vs. Runoff Curves

Chiltipin

Copano

Oso

Mission

AransasMedioSan Diego

Los OmosSan Fernando0.00

50.00

100.00

150.00

200.00

250.00

0 200 400 600 800 1000

Depth of Precipitation (mm/yr)

De

pth

of

Ex

pe

cte

d R

un

off

(m

m/y

r)

Range LandAgriculture

Urban

Stations

Mean AnnualRunoff (mm/yr )

Land Use+

Precipitation

Precipitation and Runoff Gradient

Precipitation and Runoff Gradients along Bay System

BA

B

A

1

10

100

1000

South North

Pre

cipi

tatio

n (m

m/y

r)

Precipitation

Runoff

Precipitation and Runoff Gradient fromSouth (A) to North (B) along the Bay System

Precipitation and Runoff GradientLocations in the South (A) and North (B)

Runoff Into Each Bay System

Middle Bay System24.5 m3/s34% of total flow

Entire Bay System = 72 m3/s

North Bay System40.5 m3/s56% of total flow

South Bay System7 m3/s10% of total flow

Bay System Water Balance

-150.0

-100.0

-50.0

0.0

50.0

100.0

150.0

Precip Evap Runoff Inflowfrom other

bays

Outflow tootherbays

Net Flow

Water Source

Entire Bay System

Bay System Water Balance

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

Precip Evap Runoff Inflow fromother bays

Outflow toother bays

Net Flow

W ater Source

Flow

(m^3

/s)

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

Precip Evap Runoff Inflowfrom other

bays

Outflow tootherbays

Net Flow

W ater Source

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

Precip Evap Runoff Inflow fromother bays

Outflow toother bays

Net Flow

Water Source

Flow

(m̂3/

s)

North Bay System

Middle Bay System

South Bay System

Purpose

To estimate the point and non-point source loads to the bay system

Total Constituent Loading

Land Surface LoadPoint Source Load

Atmospheric Load

Total Loads

Nueces River Load

? Sediment Load ?

Land Surface Constituent Loading

Load [Mass/Time] = Runoff [Vol/Time] x Concentration [Mass/Vol]

Land U se

EMC Table

Concentration

RunoffLoad

Land UseUSGS LandUse (1970’s)

Addition ofMissingLand Use

Updated LandUse from theTexas Parkand Wildlife

Percent Land Use

Total Study Area

Legend

North Portionof the Study Area

Middle Portionof the Study Area

South Portionof the Study Area

EMC Table

Constituent Res Comm Ind Trans Agr Range UndevTotal Nitrogen (mg/l) 1.82 1.34 1.26 1.86 4.40 0.70 1.50Total Phosphorus (mg/l) 0.57 0.32 0.28 0.22 1.30 <0.01 0.12Oil and Grease (mg/l) 1.7 9.0 3.0 0.4Copper (ug/l) 15.0 14.5 15.0 11.0 1.5 <10Chromium (ug/l) 2.1 10.0 7.0 3.0 <10 7.5Zinc (ug/l) 80 180 245 60 141 16 6

Point Sources

Texas Natural ResourcesConservation Commission (TNRCC)Water Quality Segmentation

Loads Routing

DEM StreamsModify DEM toBurn in Streams

Connect Streams to Bay System

Flow DirectionFlow Accumulation

Elevation Grid Modification Methodology

ORIGINAL ELEVATIONMODIFIED ELEVATION

KNOWN STREAM LOCATIONAND STREAM DELINEATEDFROM MODIFIED ELEVATION

GRID CELL SIZESECTION A-A

STREAM DELINEATEDFROM ORIGINAL ELEVATION

ELEVATIONRESOLUTION

GRIDCELL SIZE

PLAN

AA

Model Connection Methodology

OCEANLAND SURFACE BAY

SEGMENTSINK

ELEVATION

MSL

SECTION

PLAN

CENTROID

FLOW PATH

Load Routing Methodology

67 56 49 46 50

53 44 37 38 48

58 55 22 31 24

61 47 21 16 19

53 34 12 11 12

2 2 4 4 8

1 2 4 8 4

128 1 2 4 8

2 1 4 4 4

1 1 1 2 16

0 0 0 0 0

0 9 17 40 0

0 0 93 0 16

0 0 1 0

0 0 5 8

ELEVATION

FLOW DIRECTION

ACCUMULATED FLOW

4 5 12 17 23

3 3 10 12 16

2 2 6 8 10

0 1 4 7 8

0 0 3 4 7

LOAD

133

163

Total Constituent Loads

Input for WaterQuality Model

Connection of Both Models

Bay Water Quality

Total Load to Bay System

Percent Load for Each ConstituentTotal Load = 21,000 Kg/d

Total Nitrogen

Total Phos

Oil & Grease

Total Metals

Load Sources

0%

20%

40%

60%

80%

100%

TotalNitrogen

TotalPhosphorus

Oil andGrease

Copper Chromium Zinc

Nueces

Land

Point

Atmo

Load Contribution

0%

20%

40%

60%

80%

100%

TotalNitrogen

TotalPhosphorus

Oil andGrease

Copper Chromium Zinc

South

Middle

North

Atmospheric Contribution

Total Nitrogen

Atmospheric Load to Land Surface = 2,700 Kg/d

which is 35% of Land Surface Load from agricultural land use. This calculation is made assuming the EMC of 4.4 mg/l for agricultureand a Nitrogen concentration of 1.1 mg/l in precipitation

Purpose

To quantify the relationship between the total loads and the bay system water quality

Bay System Segmentation

Segmentation Used inthe CCBNEP Project

Clipped Segmentation fromDrs. Armstrong and Ward

Bay System Model Methodology.

WA

E (s s )A,B A B· –

Q sA,B A·

WB

E (s s )B,BND B BND· –

Q sB,BND B·

SEGMENT A

VA, KA, sA

BOUNDARY

sBND

SEGMENT B

VB, KB, sB

·K VA A· sA ·K VB B

· sB

E (s s )O,A O A· –

Q sO,A A·

Bay System Model Methodology.

dsB * VB = QA,B*sA - QB,BND*sB + EA,B*(sA - sB) + EBND,B*(sBND - sB) - KB*VB*sB + WB

dt

where: dsB = change in concentration of segment B / change in timedtVB = volume of segment B; (m3)QA,B = flow from segment A to B; (m3/s)QB,BND = flow from segment B to BND; (m3/s)sA = concentration of constituent in segment A; (mg/l)sB = concentration of constituent in segment B; (mg/l)sBND = concentration of constituent at boundary; (mg/l)EA,B = bulk dispersion coefficient between segments A,B; (m3/s)EB,BND = bulk dispersion coefficient between segments B,BND; (m3/s)KB = decay rate in segment B; (/d)WB = waste load in segment B; (kg/yr)

Water Quality Analysis

Salinity Concentration and Mass Fluxes in Corpus Christi Bay.

Fluxes

Flow of water

Advection

Dispersion

LoadsTransport of Constituents

Finite SegmentAnalysis

Observed vs. Expected

Total Phosphorus (mg/l)Total Nitrogen (mg/l)

Observed vs. Expected

Oil and Grease (mg/l) Copper (µg/l)

Observed vs. Expected

Zinc (µg/l)Chromium (µg/l)

Decay Rates (using three segment model)

K = ( QN,M*sN – QM,S* sM – QM,Oc*sM + EN,M(sN-sM) + EOc,M(sOc-sM) + ES,M(sS-sM) + WM ) / ( VM*sM )

where: K = the decay rateQN,M*sN = Advective load from the north segmentQM,S* sM = Advective load leaving the middle segment to the

south segmentQM,Oc* sM = Advective load leaving the middle segment to the

oceanEN,M(sN-sM) = dispersive load between the north and middle

segmentsEM,Oc(sM-sOc) = dispersive load between the middle segment

and the oceanEM,S(sM-sS) = dispersive load between the middle and south

segmentsWM = waste load entering the middle segmentVM*sM = load volume in the segment

Decay Rates (using three segment model)

Constituent Bay Decay Rate Ave DecaySection ( /d ) Rate ( /d )

Total Nitrogen North 0.030Middle 0.011South 0.024 0.022

Total Phosphorus North 0.013Middle 0.004South 0.009 0.009

Provisional EMC Data

Original EMC Values from USGS Study (Baird, 1996)

Total Nitrogen = 4.40 mg/lTotal Phosphorus = 1.30 mg/l

Provisional EMC Values from Agricultural Runoff Studies at King Ranch and Agricultural Field Near Edroy, TX (Mean Values Obtained from Okerman of USGS)

Total Nitrogen = 1.49 mg/lTotal Phosphorus = 0.47 mg/l

Provisional EMC ValuesTotal Nitrogen and Total Phosphorus from Land Surface Sources to Bay System Using Original and Provisional EMC Values.

Total Nitrogen Total PhosphorusOriginal Provisional Original Provisional

Segment (Kg/d) (Kg/d) (Kg/d) (Kg/d)

North 5021.27 2268.98 1283.48 498.46Middle 1184.66 530.17 338.45 151.78South 1412.24 669.7 356.19 144.38Total 7618.17 3468.85 1978.12 794.62

Total Nitrogen Reduction = 54%

Total Phosphorus Reduction = 60%

Provisional EMC ValuesTotal Nitrogen and Total Phosphorus from All Sources to Bay System Using Original and Provisional EMC Values.

Total Nitrogen Reduction = 27%

Total Phosphorus Reduction = 38%

Total Nitrogen Total PhosphorusOriginal Provisional Original Provisional

Segment (Kg/d) (Kg/d) (Kg/d) (Kg/d)

North 6576.35 3824.06 1409.7 624.68Middle 4025.84 3371.35 1203.25 1016.58South 4566.3 3823.76 496.37 284.56Total 15168.49 11019.17 3109.32 1925.82

Conclusions

Strong South-North gradient in runoff from the land surface

Nearly all water evaporates from bays, little exchange with the Gulf

Nonpoint sources are main loading source for most constituents

Nitrogen, phosphorus, oil & grease loads are consistent with observed concentrations in the bays

Metals loads from land account for only a small part of observed concentrations in bays - a reservoir of metals in the bay sediments?