Evaluation of the water erosion prediction project model

The single-storm component of the Water Erosion Prediction Project (WEPP) model is evaluated to determine how well it predicts runoff and sediment load. This is done using the hillslope mode of the WEPP model. Data from erosion plots located at Lamberton and Easton in Minnesota are used. At Lamberton, data are from experiments conducted with a rainfall simulator, while at Easton, the data are from natural rainfall events. Sensitivity analyses are performed to determine which input parameters have the greatest effect on model predictions. This is done for hydrologic and erosion parameters at Lamberton and only for hydrologic parameters at Easton. Expressions are derived to compute the sensitivity coefficients for the hydrologic parameters at Lamberton and these are compared with the values obtained from model predictions. The theoretical sensitivity coefficients compare very well with those obtained from model predictions. The model is calibrated with observed runoff values by adjusting the effective hydraulic conductivity until the model predictions and observed values are equal, predicted sediment load is then compared with observed values.