Abstract

To estimate non-point source pollution in rural, medium-sized watersheds it is necessary to describe the governing processes in a spatially-distributed way. For this purpose, the mathematical, event-based Agricultural Non-Point Source Pollution Model (AGNPS) was linked to a geographic information system (GIS). The computer simulation model simulated runoff, erosion, deposition, and nutrient delivery (nitrogen and phosphorus). The integrated system of GIS and AGNPS provided a highly effective tool for the handling of large amounts of spatial data including input and output files. The model was applied to the 129 km² Lumda Watershed located in the Vordere Vogelsberg, Germany, in order to evaluate the effects of several management strategies, which are intended to reduce sediment and nutrient yield. All model outputs were available for each geographic location within the watershed. The main advantage of AGNPS over older erosion prediction technologies, like the Universal Soil Loss Equation (USLE), is its capabilities to estimate off-site effects as well as on-site effects. We are presently working on the calibration and validation of the AGNPS model.