UNCERTAINTY ANALYSIS OF THE WEPP SOIL EROSION MODEL

摘要: ABSTRACT Predictions from hydrologic and erosion models contain a large degree of uncertainty. The Modified Point Estimate Method (Harr, 1989) used in conjunction with response surface exploration technique (Brooks, 1958) provides simple, computationally efficient, powerful tool for evaluating uncertainty predictions by natural-resource models. method allows analysis number input parameters which may be correlated the exact parameter distribution is unknown. was applied to Water Erosion Prediction Project single rainfall-event model. Sixty treatment combinations were selected determine WEPP output uncertainties wide range soil, crop, management, topographic, storm conditions. levels randomly span entire factorial space 28 inputs, but finite combinations. Five outputs studied: peak runoff rate, average soil loss, deposition, sediment yield, specific enrichment ratio. Maximum uncertainties, given coefficient variation, determined each 60 treatments. coefficients variation ratio 196, 267, 323, 47%, respectively. Average same set variables 65, 99, 106, 13%, Coefficient less larger events, account percentage total loss at location over extended time periods. Significant, positive correlations existed between indicating that yield directly related rate.