A comparison of EPM and WEPP models for estimating soil erosion of Marmeh Watershed in the south Iran.

Soil erosion and sediment yield is one of the main challenges in Iran, and quantity estimation of them is an important issue. Two models (the empirical Erosion Potential Method (EPM) and the physical Water Erosion Prediction Project (WEPP) were applied to predict soil loss and sediment yield for the Marmeh Watershed. After watershed modelling, the simulated sediment yield values were compared with the observed sediment yield values. In the calibration and validation periods, the Nash–Sutcliffe model efficiency (ENS) values for the WEPP and EPM were 0.977 and 0.981, and 0.903 and 0.927 for WEPP and EPM, respectively. Also, deviation (Re) between the mean simulated and observed sediment values for the WEPP and EPM models were -8.5% and -2.4%, and -2.0% and -0.5%, respectively. These results indicate that the WEPP simulations were better than EPM, and could be used for soil loss and sediment yield estimation in the Marmeh Watershed.