Efficiency of WEPP Model for Prediction of Soil Erosion and Runoff on Rainfed Land in a Semi-Arid Region

Document Type : Research Paper

Author

Assistant Professor, Agriculture and Natural Resource Research Center of Kermanshah

Abstract

The process-based WEPP model can predict all effective variables of soil erosion physically using mathematical equations, especially in arable lands. The main objectives of this study were to determine the capability of hill-slope version of WEPP model in runoff and soil erosion estimation on rainfed lands and its potential in simulating the different management practices effects on soil erosion. This research was conducted in rainfed area of Kabode region, across the Gharasoo watershed. Runoff and sediment collection plots with dimension of 10×3 meter in three replications were installed on the slopes of 6%, 12%, 16%, and 20%. Climate data recorders including rain gauge and Maximum and Minimum temperature recorders were installed in the site to record daily climate data. Additional climate data requirements including wind velocity and direction, solar radiation, and dew point temperature was obtained from Kermanshah synoptic station. Soil erosion and runoff was estimated in each plot for different hill slopes by the v2008.9 version of WEPP. Results from the model assessment indicated that the runoff prediction accuracy was increased with increasing slope steepness such that the negative values of Nash-Sutcliff index in the 6% and 12% slope and the high RMSE’s of, respectively, 3.16 and 4.82 liter indicated lower accuracy of the model in runoff prediction for these slopes. In all plots, with the exception of plots on 6% slope, runoff was under- estimated. Also, maximum accuracy for soil erosion prediction was in 16% slope plots and the minimum efficiency of the model was in 20% slope, where the under-estimation error was 7.5 kg per plot per year and the values of Nash-Sutcliff index were negative. 

Keywords


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