Modeling of Atrak Watershed Runoff Using the SWAT Model of SUFI-2 Algorithm

Soil erosion and surface runoff generation is a serious environmental threat to sustainable development and agriculture, that may lead to a reduced soil fertility, nutrient loss, and reduced plant performance in the agricultural areas. In recent years, the use of modeling is introduced as a means to evaluate the impact of erosion reduction measures. SWAT is a conceptual and distribution model developed to predict and estimate surface runoff, sediment brought, qualitative characteristics of water, as well as to predict the effects of different management measures in the basin. The aim of this study was to investigate the usefulness of SWAT model to estimate the average daily flow rate and calibrate and validate the model in Atrak watershed at Khorasan Razavi North Khorasan provinces. Calibration and uncertainty analysis of the model were performed using SUFI-2. Indicators P-factor, R-factor, br2, and r2 were used in order to assess the ability of SWAT model to simulate Atrak watershed runoff. Runoff data of six hydrometric stations in 1975-1991 were used for calibration and validation of this basin. The results showed that the monthly runoff at calibration stage, the coefficients P-factor, R-factor, br2, and r2 in output basin was 0.73, 1.15, 0.53, and 0.56, and in the validation stage was 0.77, 1.3, 0.48 and 0.58, respectively. The best results were obtained in Shirabad station and the weakest results in Gharehkahnbandi station. Overall calibration results show that the SWAT model can be a useful tool in river flow rate simulation.