Evaluation of stochastic weather parameters for Minnesota and their impact on WEPP

The Water Erosion Prediction Project (WEPP) model predicts soil loss and deposition from overland flow and concentrated flow in small channels as well as sediment deposition in an impoundment. The WEPP model uses a stochastic weather generator to provide daily weather information. It also has an algorithm to define a storm hyetograph from information provided by the stochastic weather generator. Observed weather data were gathered for several random sites in Minnesota and compared to predicted data by WEPP. Rainfall intensities were compared using the Depth-Duration Frequency representation. The predicted non-precipitation values of WEPP are in good agreement with those observed. The daily precipitation depths are also in good agreement with the observed values. However, for duration less than twenty-four hours, the WEPP depths were greater than those observed.