The Evaluation Efficiency of WEPP Model to Predict Sediment Yield in Sulachai Watershed-Ardabil

Water and soil are the most important natural resources of each country and are the foundation of human life. Soil erosion and sediment production causes reduced fertility of arable land and therefore are threatening human life On the other hand, increasing sedimentation amount in watersheds has an important role in reducing useful life of dams and dewatering reducing capacity of them. Thus the study of soil erosion and the estimation of the output sediment watershed are necessary. Researches carrying out the quantitative assessment of sediment production using the different models are one of solutions that through which one can partly control and minimize the amount of this phenomenon. The aim of this research is to evaluate efficiency of the WEPP model in estimation the output sediment Sulachai watershed. The method in WEPP model this is that, to the beginning the file related to each of the model parameters such as climate, soil, topography, management and drainage is created and entered on the software GeoWEPP and finally sediment load is calculated. WEPP model has required performance in sediment estimation for the three-scale slope, catchment area and flow-direction. Estimated sediment by each of the above three scales, is 0.213, 0.178 and 0.785 respectively, and for observed sediment is about 0.241 ton/hectares/year. The results of the comparison of WEPP model with the observed sediment indicated that from among the scales available in the WEPP model, slope and catchment area scales were closer to the amount of sediment observed and have offered more acceptable results than the flow-direction scale.