WATER EROSION PREDICTION PROJECT (WEPP) RANGELAND HYDROLOGY COMPONENTEVALUATION ON A TEXAS RANGE SITE

The USDA-Water Erosion Prediction Project (WEPP) is a new technology b ased on the fundamentals of hydrology, soil physics, plant science, hy draulics, and erosion mechanics, WEPP hydrology includes simulation of excess rainfall using the Green and Ampt infiltration equation, surfa ce runoff routing, evapotranspiration, percolation, and surface draina ge, Hydrometeorological, soil, topography, and vegetation data from a range in Texas were used to test the WEPP rangeland hydrology model. M easured surface runoff and root zone soil water content from the site were compared with the simulated results of the WEPP model, The result s indicate that the WEPP model (version 93.0) is capable of simulating soil water content and storm runoff, The Nash and Sutcliffe coefficie nt, NSR, between measured and simulated root zone soil water content a nd storm runoff was .88 and .84, respectively, for the bare ground plo ts, However, for the plots with herbaceous vegetation the discrepancy between model simulated storm runoff and soil water content was more t han expected (NSR = .46 and NSR = .53, respectively).