The Himalayan rivers are the major source of freshwater resources and have a tremendous potential for hydroelectric generation. However, assessing the water availability under climate change is challenging due to data scarcity, undulating topography, and complex climatic conditions. SWAT modeling investigates all potential consequences of variations in climate on the hydrological fluxes in the Upper Bhagirathi River Basin. Two global circulation models (GCMs) with three different climatic scenarios were employed. Quantile mapping has been used to correct the bias of GCM data. The developed model accurately simulated streamflow during calibration and validation at daily (NSE = 0.79 - 0.74, r = 0.89-0.87, and RMSE = 61.95 m