WSM Model Optimization in Soil Erosion and Sediment Estimating, by Coefficient Modifying and using Rainfall Simulator in Nir Watershed-Yazd Province

Soil erosion leads to washing topsoil, organic matter and soil fertility will decrease eventually. In order to combat erosion and loss of soil, conservation and watershed sediment generation in the NIR region, based on the WSM modeling was performed to estimate the severity of soil deposits. The model with six factors was scored for each work unit. Usually suitable model for certain areas that used them in different situations, needs to model coefficients be calibrated in the study area. For calibration, were measured the amount of precipitation from the model (estimated) and the simulated rain (objective) per work units in this watershed. The results were showed that in some work units the amount of estimated is more than 10 times versus the amount of real data (model with overestimating). The coefficients correction was done by optimizing in the Solver, with convergence (10-4), mutation and forward derivative (0.075) technology, with default values. With using the correction coefficients in the model and establishing a revised model, estimated sediment was closer to the objective values and were increased the correlation between estimate and the observed. Thus the modified model for areas with similar soil and climatic conditions in Yazd province, which has been used with caution. It is suggested to improve the coefficients, with the modified model results in a basin with actual values, to evaluate more confidently be used as local models.