Distribution of ground cover and its effects on runoff and sediment yield in the WEPP model

Abstract

New methods were tested to evaluate the ground cover parameters used in the WEPP model. Rainfall simulator plot data, collected from fifteen rangeland ecosystems across the western United States, were used to evaluate modifications to the ground cover components for rill and interrill areas in the model. Observed and predicted values of average sediment yield were compared for six different configurations of the model. The modifications made to WEPP to incorporate measured ground cover distributions resulted in a lower r2 for predicted sediment yield than any of the configurations in which ground cover distribution was not modified. This result was due to a reduction in the calculated value of total interrill ground cover. The model equations used to adjust interrill erodibility for the effect of interrill ground cover were adversely affected. The result was that interrill erodibility values were increased for many of the plots tested.