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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #57126
Title: GIS-BASED MODELING OF PHOSPHORUS OUTPUT FROM A NORTHEASTERN UPLAND AGRICULTURAL WATERSHED

Author
item Zollweg, James
item Gburek, William
item Pionke, Harry
item Sharpley, Andrew

Submitted to: Water Quality Modeling International Symposium
Publication Type: Proceedings
Publication Acceptance Date: 4/5/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Nutrients and chemicals transported from agricultural land to waterways in surface runoff is a major problem. Proper management requires identification of those areas most likely to be sources of these pollutants. We have developed a new computer model which is able to predict the amount of phosphorus (P) exported from a watershed and the areas where that P originates. Model results illustrate that the areas of the watershed controlling P export are consistently a relatively small and definable portion of the watershed. Use of this model as a management tool will provide significant savings because expensive ameliorative measures can be directed to those specific locations where the greatest potential for pollution generation exists.

Technical Abstract: A GRASS GIS-based methodology was developed for modeling the extent and contributions of phosphorous (P) exporting areas of a watershed. SMoRMod, an existing physical process based, variable source area runoff model is supplemented with algorithms for P availability and transport by surface runoff. The distributed modeling approach employed enables identification of source areas of runoff and P, as well as generation of the runoff hydrograph and calculation of the total delivery of P to the outlet. The model is verified by comparing simulated P losses with measured values of flow rate and P concentration in streamflow within a 25.7-ha agricultural watershed in east-central Pennsylvania. Additional model results illustrate that zones of runoff production, and consequently the areas of the watershed controlling P export, are consistently a relatively small and definable portion of the watershed. Finally, the model is used to show how wchanging management practices in these small areas can reduce P export fro the watershed.