Title: Nonpoint Source Pollution
1Nonpoint 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
2Adapt Water to the Land System
Water Characterization (water yield, flooding,
groundwater, pollution, sediment)
Land Characterization (Land use, Soils, Climate, T
errain)
Non Point Source Pollution (mean annual flows and
pollutant loads)
3Possible Land-Water Transform Coefficients
4Expected Mean Concentration
- EMC Load Mass/Flow Volume either on a single
event basis or as an annual average
L
Q
C
L(t)Q(t)C(t)
0
T
0
T
T
0
EMC M/V
Concentration
Load
Flow
5 Map-Based Surface Water Runoff
Estimating the surface water yield by using a
rainfall-runoff function
Runoff, Q (mm/yr)
Q
P
Runoff Coefficient C Q/P
Accumulated Runoff (cfs)
Precipitation, P (mm/yr)
6Water Quality Pollution Loading Module
Load Mass/Time Runoff Vol/Time x
Concentration Mass/Vol
Precip.
Runoff
DEM
LandUse
Accumulated Load
EMC Table
Load
Concentration
7Expected Mean Concentration
Land Use
EMC
Table derived from USGS water quality monitoring
sites
8Water Quality Land Surface -Water Body Connection
Bay Water Quality
Total Constituent Loads
Input for Water Quality Model
9Readings 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 - Masters theses of
- Christine Dartiguenave http//www.crwr.utexas.edu/
gis/gishyd98/library/dartig/rpt97_6.html - Ann Quenzer http//www.crwr.utexas.edu/gis/gishyd9
8/library/quenzer/rpt98_1.html - Patrice Melancon http//www.crwr.utexas.edu/crwr/r
eports/rpt99_3/rpt99_3.html - Katherine Osborne http//www.crwr.utexas.edu/crwr
/reports/rpt00_10/rpt00_10.htm
10 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
Program Ferdinand Hellweger Dr. Nabil Eid Dr.
George Ward Dr. Neal Armstrong
11Purpose
- 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
12Basic Concept
Steady-State Model
Linkage of the Two Models
Calculate Flow and Total Loads
13Purpose
- To determine the rainfall/runoff relationship
14Watershed Delineation
Sub-Watersheds
15Precipitation
Merged Precipitation Files
Precipitation Trend
Oregon State University
over Bay System
Precipitation Data
16Regression Inputs and Outputs
17Surface Water Runoff
18Surface Water Runoff
Land Use
Precipitation
19Precipitation and Runoff Gradient
Precipitation and Runoff Gradient from South (A)
to North (B) along the Bay System
Precipitation and Runoff Gradient Locations in
the South (A) and North (B)
20Runoff Into Each Bay System
North Bay System 40.5 m3/s 56 of total flow
Entire Bay System 72 m3/s
Middle Bay System 24.5 m3/s 34 of total flow
South Bay System 7 m3/s 10 of total flow
21Bay System Water Balance
Entire Bay System
22Bay System Water Balance
North Bay System
Middle Bay System
South Bay System
23Purpose
- To estimate the point and non-point source loads
to the bay system
24Total Constituent Loading
Land Surface Load
Point Source Load
Atmospheric Load
? Sediment Load ?
25Land Surface Constituent Loading
Load Mass/Time Runoff Vol/Time x
Concentration Mass/Vol
26Land Use
USGS Land
Use (1970s)
Addition of
Missing
Land Use
27Percent Land Use
Total Study Area
Legend
28EMC Table
29Point Sources
Texas Natural Resources Conservation Commission
(TNRCC) Water Quality Segmentation
30Loads Routing
31Elevation Grid Modification Methodology
32Model Connection Methodology
33Load Routing Methodology
34Connection of Both Models
Bay Water Quality
Total Constituent Loads
Input for Water Quality Model
35Total Load to Bay System
36Load Sources
37Load Contribution
38Atmospheric 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
agriculture and a Nitrogen concentration of 1.1
mg/l in precipitation
39Purpose
- To quantify the relationship between the total
loads and the bay system water quality
40Bay System Segmentation
Clipped Segmentation from Drs. Armstrong and Ward
Segmentation Used in the CCBNEP Project
41Bay System Model Methodology.
42Bay System Model Methodology.
43Water Quality Analysis
Salinity Concentration and Mass Fluxes in
Corpus Christi Bay.
Finite Segment Analysis
Flow of water
Transport of Constituents
Fluxes
Loads
Advection
Dispersion
44Observed vs. Expected
Total Nitrogen (mg/l)
Total Phosphorus (mg/l)
45Observed vs. Expected
Oil and Grease (mg/l)
Copper (µg/l)
46Observed vs. Expected
Zinc (µg/l)
Chromium (µg/l)
47Decay Rates (using three segment model)
48Decay Rates (using three segment model)
49Provisional EMC Data
Original EMC Values from USGS Study (Baird,
1996) Total Nitrogen 4.40 mg/l Total
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/l Total Phosphorus 0.47 mg/l
50Provisional EMC Values
Total Nitrogen and Total Phosphorus from Land
Surface Sources to Bay System Using Original and
Provisional EMC Values.
Total Nitrogen Reduction 54 Total Phosphorus
Reduction 60
51Provisional EMC Values
Total Nitrogen and Total Phosphorus from All
Sources to Bay System Using Original and
Provisional EMC Values.
Total Nitrogen Reduction 27 Total Phosphorus
Reduction 38
52Conclusions
- 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?