2. Nonpoint Source Pollution u Some basic principles u 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

3. Adapt Water to the Land System Land Characterization (Land use, Soils, Climate, Terrain) Water Characterization (water yield, flooding, groundwater, pollution, sediment) Non Point Source Pollution (mean annual flows and pollutant loads)

4. Possible Land-Water Transform Coefficients Water Land

5. Expected Mean Concentration u EMC = Load Mass/Flow Volume either on a single event basis or as an annual average QC TT L 0 0 0 T EMC =M/V Flow ConcentrationLoad L(t)=Q(t)*C(t)

6. Map-Based Surface Water Runoff Runoff, Q (mm/yr) Precipitation, P (mm/yr) Accumulated Runoff (cfs) P Q Runoff Coefficient C = Q/P

7. Water Quality: Pollution Loading Module DEM Precip. Runoff LandUse EMC Table Concentration Load Accumulated Load Load [Mass/Time] = Runoff [Vol/Time] x Concentration [Mass/Vol]

8. Expected Mean Concentration Land Use EMC Table derived from USGS water quality monitoring sites

9. Total Constituent Loads Input for Water Quality Model Water Quality: Land Surface -Water Body Connection Bay Water Quality

10. Readings on Nonpoint Source Pollution (Handbook of Hydrology on reserve in Engr Library) u Handbook of Hydrology: Sec 14.1 and 14.2 on nonpoint source pollution sources u Handbook of Hydrology: Sec 28.6 on design for water quality enhancement u 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 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

11. 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

12. Purpose u To determine the rainfall/runoff relationship u To estimate the point and non-point source loads to the bay system u To quantify the relationship between the total loads and the bay system water quality

13. Basic Concept Point and Non-point Estimation Total Loads Routing Water Quality Calculate Flow and Total Loads Linkage of the Two Models Steady-State Model

14. Purpose u To determine the rainfall/runoff relationship

15. Watershed Delineation Sub-Watersheds

16. Precipitation + = Precipitation Trend over Bay System Merged Precipitation Files Oregon State University Precipitation Data

17. Regression Inputs and Outputs

18. Surface Water Runoff

19. Mean Annual Runoff (mm/yr) Land Use + Precipitation

20. 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)

21. Runoff Into Each Bay System Middle Bay System 24.5 m 3 /s 34% of total flow Entire Bay System = 72 m 3 /s North Bay System 40.5 m 3 /s 56% of total flow South Bay System 7 m 3 /s 10% of total flow

22. Bay System Water Balance Entire Bay System

23. Bay System Water Balance North Bay System Middle Bay System South Bay System

24. Purpose u To estimate the point and non-point source loads to the bay system

25. Total Constituent Loading Land Surface Load Point Source Load Atmospheric Load ? Sediment Load ?

26. Land Surface Constituent Loading Load [Mass/Time] = Runoff [Vol/Time] x Concentration [Mass/Vol]

27. Land Use USGS Land Use (1970’s) Addition of Missing Land Use

28. Percent Land Use Total Study Area Legend

29. EMC Table

30. Point Sources Texas Natural Resources Conservation Commission (TNRCC) Water Quality Segmentation

31. Loads Routing

32. Elevation Grid Modification Methodology

33. Model Connection Methodology

34. Load Routing Methodology

35. Total Constituent Loads Input for Water Quality Model Connection of Both Models Bay Water Quality

36. Total Load to Bay System

37. Load Sources

38. Load Contribution

39. 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

40. Purpose u To quantify the relationship between the total loads and the bay system water quality

41. Bay System Segmentation Segmentation Used in the CCBNEP Project Clipped Segmentation from Drs. Armstrong and Ward

42. Bay System Model Methodology.

44. Water Quality Analysis Salinity Concentration and Mass Fluxes in Corpus Christi Bay. Fluxes Flow of water Advection Dispersion Loads Transport of Constituents Finite Segment Analysis

45. Observed vs. Expected Total Phosphorus (mg/l) Total Nitrogen (mg/l)

46. Observed vs. Expected Oil and Grease (mg/l)Copper (µg/l)

47. Observed vs. Expected Zinc (µg/l)Chromium (µg/l)

48. Decay Rates (using three segment model)

50. 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

51. 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%

52. 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%

53. Conclusions u Strong South-North gradient in runoff from the land surface u Nearly all water evaporates from bays, little exchange with the Gulf u Nonpoint sources are main loading source for most constituents u Nitrogen, phosphorus, oil & grease loads are consistent with observed concentrations in the bays u Metals loads from land account for only a small part of observed concentrations in bays - a reservoir of metals in the bay sediments?