Water Erosion Prediction Project (WEPP) Rangeland Hydrology Component Evaluation on a Texas Range Site

Abstract

The USDA-Water Erosion Prediction Project (WEPP) is a new technology based on the fundamentals of hydrology, soil physics, plant science, hydraulics, and erosion mechanics. WEPP hydrology includes simulation of excess rainfall using the Green and Ampt infiltration equation, surface runoff routing, evapotranspiration, percolation, and surface drainage. Hydrometeorological, soil, topography, and vegetation data from a range in Texas were used to test the WEPP rangeland hydrology model. Measured surface runoff and root zone soil water content from the site were compared with the simulated results of the WEPP model. The results indicate that the WEPP model (version 93.0) is capable of simulating soil water content and storm runoff. The Nash and Sutcliffe coefficient, NSR, between measured and simulated root zone soil water content and storm runoff was .88 and .84, respectively, for the bare ground plots. However, for the plots with herbaceous vegetation the discrepancy between model simulated storm runoff and soil water content was more than expected ( NSR = .46 and NSR = .53, respectively).