Calibration of FSM Empirical Model Using Sediment Survey of in the Northeastern of Iran

One of the important problems of Iran which causes soil quality and quantity decrease is soil erosion and sediment yield. Soil conservation measures are needed to reduce the adverse effects of this phenomenon. Therefore, it is necessary to know about soil erosion and sediment yield in different regions and should identify critical areas. Due to the lack of gauge stations for measuring sediment amounts in most of the country's watersheds and inadequate data, empirical models such as FSM model are important tools for producing this information layer. Therefore, the main purpose of this research is to edit and adapt the conditions of the FSM model to nature in the level of the Northeastern basins of Iran. In the implementation of this plan, at first, some of the water storage sites with minimum 10 year old structure that show no evidence overflow of water and sediment were selected in the Golestan and Khorasan-Razawi provinces. These watersheds were studied and the required information layers for the FSM experimental model were prepared and sediment delivery values of the basins were estimated. Estimated values of this model was compared with the values obtained by measuring sediment reservoirs of small dams. Based on the results of the sensitivity analysis of the model, it was observed that the five factors of the model effects on the sediment amount is not high and the amount of area changes have a great influence on the sediment yield. Also, according to the results, the use of the main model in Spain, provides a far-reaching estimate of reality. It was also concluded that if the model calibrated in the Northeastern basins, the efficiency of the model increases dramatically, so that the NSE index ranged from -2115.46 to 0.62 and the RRMSE index from 73.78 to 0.57 arrives. Also, based on the results, calibration of the model based on the dominant climate is a solution to improve efficiency, so that in the regions with Mediterranean climate, the NSE and RRMSE indices are 0.83 and 0.52 respectively, which indicates the proper performance of the model in these areas. In semi-arid climates, it was observed that the NSE and RRMSE indices were equal to 0.86 and 0.31, respectively, indicating the performance of the model in these areas.Keywords: FSM model, sedimentation, erosion, watershed, sensitivity analysis and reservoir sediments.