SWAT Modeling to Assess Water Availability in the Command Area of the Gandak River Basin, India

It is essential to analyse water availability in a sub-basin for the management of water resources. In this study, a sub-basin of the Gandak River, with an area of 973.54 km2, has been selected to study water availability using a SWAT model with remote sensing and GIS support. For the analysis, hydrological and meteorological data for the year 2002 to 2021 have been used in addition to the land-use/land cover maps, soil map, and slope map. The SWAT model was simulated throughout a twenty-one-year period (from 2002 to 2021). To determine the most important watershed parameters, a sensitivity analysis of the model was carried out. Calibration was performed using data from 2002 to 2014 and validated from 2015 to 2021. The following statistical parameters were measured: Coefficient of determination (R2), Root Mean Square Error (RMSE), Percent Bias (PBIAS), and Nash Sutcliffe Efficiency (NSE). The results obtained for these statistical parameters indicate that the model results are satisfactory.