Evaluation of the water erosion prediction project (WEPP) model for hillslopes

The USDA-Water Erosion Prediction Project (WEPP) computer model is process-based soil erosion prediction technology. Process-based erosion models provide several advantages over empirically based erosion prediction technology, including most notably. 1) capabilities for estimating spatial and temporal distributions of net soil loss, 2) more reliable extrapolation to ungauged areas, and 3) the ability to better predict off-site delivery of sediment, including particle size information. The purpose of this paper is to present an evaluation of the WEPP erosion model as applied to the case of soil loss on hillslopes. Cases where deposition is active were not considered. WEPP was compared with the Universal Soil Loss Equation and its revision, RUSLE, relative to soil erodibility and selected agricultural land use effects on erosion. This paper also presents data from natural runoff plots at nine locations evaluated relative to the WEPP model predictions. Plot data were taken from the National Repository of Soil Erosion Data located at the Agricultural Research Service's National Soil Erosion Research Laboratory. Historical climate and management information, as well as representative slope and soil information, was used to build input Nea for the model. A total of 544 erosion years of data from 64 plots were used. These data are among the most reliable from the current data base of soil erosion in the US. Results indicated that WEPP followed the trends in erodibility and cropping factors as represented by USLE and RUSLE. Comparisons of predictions with measured data were reasonable relative to the expected degree of accuracy for erosion prediction.