An Integrated Assessment of Non-Point Source Pollution in Large Basins




Moltz, Heidi L.N.

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Determining the location of priority pollutant-generation areas is central to the success and cost-effectiveness of non-point source pollution control programs. This research developed a novel integrated methodology for assessing non-point source pollution (NPSP) in large basins, building on Geographic Information Systems (GIS), hydrologic modeling, organizational surveys, and spatially explicit census data analyses. The study area was the United States portion of the Rio Grande Basin. An erosion index and run-off index were developed with the use of GIS, to identify areas at high risk for producing NPSP. The erosion index utilizes an adaptation of the Universal Soil Loss Equation, verified using rainfall simulation data. The run-off index utilized the Curve Number method, an empirical rating of a large number of soils and vegetative covers, which has received a great deal of verification since its inception. Once located and evaluated with initial geospatial and risk analyses, one selected priority area was studied with more detailed hydrologic modeling to demonstrate local-level analyses. Hydrologic modeling, in turn, provided area-specific detailed assessments of hydrologic processes and pollutant loadings, as well as information on the potential efficacy of control practices and land use changes applied at the field, farm, and sub watershed scale not easily obtainable using GIS alone. Detailed hydrologic assessments were conducted in the Santa Fe Watershed, an identified high priority area in the Rio Grande Basin, using the Hydrologic Simulation Program - Fortran. Because hydro logic assessments alone cannot successfully prevent NPSP, a survey of organizations influencing and implementing NPSP policy was developed to inform hydrologic model pollutant selection and scenario development in the Santa Fe Watershed. Spatially explicit demographic and socioeconomic data were then obtained to tailor pollution prevention programs to community-specific characteristics. Two identified issues of concern for program implementation in the Santa Fe Watershed were overcoming the "digital divide" and the language barrier through the use of appropriate and targeted outreach strategies. These GIS assessment was capable of identifying high risk areas for NPSP generation in the Rio Grande Basin. In combination, the hydrologic modeling and social assessment accurately simulated and predicted the generation, movement, and prevention of NPSP within the Santa Fe River watershed, an identified high risk area within the Rio Grande Basin, over the period of record, as a means of identifying solutions that reduce pollutant loads and are tailored to the needs of the local community.



Rio Grande Watershed, hydrologic models, watersheds, nonpoint source pollution, Santa Fe River


Moltz, H.L.N. (2009). An integrated assessment of non-point source pollution in large basins (Unpublished dissertation). Texas State University-San Marcos, San Marcos, Texas.


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