Nonpoint Source Pollution

1
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

2
Adapt 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)
3
Possible Land-Water Transform Coefficients
4
Expected 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)
6
Water Quality Pollution Loading Module
Load Mass/Time Runoff Vol/Time x
Concentration Mass/Vol
Precip.
Runoff
DEM
LandUse
Accumulated Load
EMC Table
Load
Concentration
7
Expected Mean Concentration
Land Use
EMC
Table derived from USGS water quality monitoring
sites
8
Water Quality Land Surface -Water Body Connection
Bay Water Quality
Total Constituent Loads
Input for Water Quality Model
9
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
• 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
11
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

12
Basic Concept
Steady-State Model
Linkage of the Two Models
Calculate Flow and Total Loads
13

Purpose

• To determine the rainfall/runoff relationship

14
Watershed Delineation
Sub-Watersheds
15
Precipitation
Merged Precipitation Files
Precipitation Trend
Oregon State University
over Bay System
Precipitation Data


16
Regression Inputs and Outputs
17
Surface Water Runoff

18
Surface Water Runoff
Land Use

Precipitation
19
Precipitation 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)
20
Runoff 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
21
Bay System Water Balance
Entire Bay System
22
Bay System Water Balance
North Bay System
Middle Bay System
South Bay System
23

Purpose

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

24
Total Constituent Loading
Land Surface Load
Point Source Load
Atmospheric Load
? Sediment Load ?
25
Land Surface Constituent Loading
Load Mass/Time Runoff Vol/Time x
Concentration Mass/Vol
26
Land Use
USGS Land
Use (1970s)
Addition of
Missing
Land Use
27
Percent Land Use
Total Study Area
Legend
28
EMC Table
29
Point Sources
Texas Natural Resources Conservation Commission
(TNRCC) Water Quality Segmentation
30
Loads Routing
31
Elevation Grid Modification Methodology
32
Model Connection Methodology
33
Load Routing Methodology
34
Connection of Both Models
Bay Water Quality
Total Constituent Loads
Input for Water Quality Model
35
Total Load to Bay System
36
Load Sources
37
Load Contribution
38
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
agriculture and a Nitrogen concentration of 1.1
mg/l in precipitation
39
Purpose

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

40
Bay System Segmentation
Clipped Segmentation from Drs. Armstrong and Ward
Segmentation Used in the CCBNEP Project
41
Bay System Model Methodology.
42
Bay System Model Methodology.
43
Water Quality Analysis
Salinity Concentration and Mass Fluxes in
Corpus Christi Bay.
Finite Segment Analysis
Flow of water
Transport of Constituents
Fluxes
Loads
Advection
Dispersion
44
Observed vs. Expected
Total Nitrogen (mg/l)
Total Phosphorus (mg/l)
45
Observed vs. Expected
Oil and Grease (mg/l)
Copper (µg/l)
46
Observed vs. Expected
Zinc (µg/l)
Chromium (µg/l)
47
Decay Rates (using three segment model)
48
Decay Rates (using three segment model)
49
Provisional 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
50
Provisional 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
51
Provisional 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
52
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?