Climate change-induced hydrological partitioning and implications for drought dynamics in the monsoon-dominated Seonath Basin

Watershed hydrology may face more difficulties in future due to changes in flow patterns, water-balance partitioning, and drought-related dynamics forced by climate change. This study uses a multi-model CMIP6 framework linked with SWAT hydrological modelling to examine climate change-induced hydrological responses and implications for drought behaviour in the Seonath Basin. A compromise-programming technique was used to evaluate 13CMIP6-GCMs, and MPI-ESM1-2-HR emerged as the most suitable model for recreating historical temperature and precipitation. A calibrated SWAT model was developed by bias-corrected projections under the SSP2-4.5 scenario that performed well during calibration (R²=0.87–0.91; NSE=0.86–0.90). Future climate simulations indicate substantial hydrological reorganization. A 15% increase in mean annual precipitation (1189 → 1365 mm) results in a 78% increase in surface runoff (218 → 389 mm), a more than fourfold increase in percolation to the shallow aquifer (62 → 321 mm), and an increase in deep aquifer recharge from 3.1 mm to 16.1 mm. Streamflow-to-precipitation rises from 0.25 to 0.43 while evapotranspiration-to-precipitation rises from 0.70 to 0.38, according to water-balance ratios at the basin outflow, suggesting faster hydrological performance and shorter soil-water residence times. Under situations of increased rainfall, the percolation-to-precipitation ratio rises significantly from 0.05 to 0.24, indicating improved subsurface routing.