Sensitivity analysis of the WEPP Watershed model

Abstract

Uncertainty in the hydrologic and soil erosion predictions of the WEPP Watershed model due to errors in model parameter estimation was identified through a sensitivity analysis based on the Monte-Carlo method. Identification of parameter sensitivities provides guidance in the collection of parameter data in places where the model is intended to simulate soil erosion. Changes in model predictions caused by changes in model parameters were quantified for model applications in semi-arid rangeland watersheds. The magnitude of the changes in model parameters was defined by the spatial variability of parameters in a watershed. Model sensitivities in predicting overland flow and soil erosion on hillslopes and channels are presented considering rainfall characteristics. The results show that WEPP predictions are very sensitive to attributes that define a storm event (amount, duration, and ip). Model sensitivity to soil erosion parameters also depends of the type of storm event.