Investigation of the water balance of Fakhrabad watershed using SWAT model

Water resources management, especially in watersheds without statistics all data, requires the recognition of hydrological processes, especially runoff, as one of the most important and most practical phases of the hydrological cycle. The aim of this study was to determine the efficiency and usability of the SWAT model in simulating the water balance of the Fakhrabad watershed. For the initial implementation of the model, the data required for the model implementation include meteorological data (precipitation, minimum and maximum temperature, relative humidity, and wind speed), baseline maps of the region (digital elevation map, land use, slope and soil map) and monthly discharge data of Fakhrabad hydrometric station. Were used. After the initial implementation of the SWAT model, the output was called to SWAT-CUP software for calibration and validation after sensitivity analysis, the model was implemented to determine the sensitive parameters and the results were reviewed. Calibration and validation were performed for the period 1998-2014 and the accuracy of monthly runoff simulation using the coefficient of determination (R2) and Nash Sutcliffe (NSE) for the calibration phase of 0.73 and 0.71 and for the validation phase of 0.54 and 0.53 was obtained. Acceptable values were also obtained for the uncertainty assessment indicators. P-factor and R-factor were 0.56 and 0.65 for the calibration period and 0.54 and 0.68 for the validation period, respectively. The final results showed that on average of 67% of precipitation enters the atmosphere through evapotranspiration, 23% enters the canals as surface run off and subsurface flow. The results show the efficiency of the SWAT model in simulating the water balance of Fakhrabad watershed and helps to more accurately programing water resources in this basin.