Hydrological modelling of a mountainous watershed: simulating streamflows under present and projected climate conditions

Streamflow is significantly influenced by the increased temperature and rainfall inconsistency due to climate change. This study assesses the impacts of climate change on water availability and streamflow dynamics during the periods 2030–2069 and 2070–2099 for two greenhouse gas trajectories (SSP245 and SSP585) in the lower catchment of the Upper Sutlej River Basin (USRB). This study integrates data from the Coupled Model Inter-comparison Project Phase 6 (CMIP6) General Circulation Models (GCMs) with the SWAT hydrological model. This approach analyzes the complex interactions between climate variables and hydrological processes. NASA NEX-GDDP-CMIP6 Bias-corrected statistically downscaled data at 0.25° X 0.25° grid resolution are used. Under SSP245, projected streamflow for near future 2030 to 2069 shows increases up to 56.097% in December, while decreases reach -9.420% in August. For far future 2070 to 2099, increases are observed up to 41.846% in December, with decreases up to -25.670% in August. Under SSP585, for near future 2030 to 2069, decreases range from -7.616% in May to -13.614% in August. For far future 2070 to 2099, decreases range from -12.386% in October to -25.670% in August, while increases reach 46.211% in November. The insights derived are crucial information for assessing water resource vulnerability to climate change in mountainous regions.