Multimodel analysis of climate-induced flow variability in transboundary tropical basins

ABSTRACT Graphical abstract which show study area on top left, calibration site performances on bottom left, climate scenarios and response of water resources parameters in the middle and climate elasticity performance as well as recommendations on the right. Robust water resources planning requires integrated assessments, yet combined hydrological model and multimodel elasticity studies remain limited. This study coupled the Soil and Water Assessment Tool plus (SWAT+) with downscaled and bias-corrected Coupled Model Intercomparison Project Phase 6 (CMIP6) projections under Shared Socioeconomic Pathway scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). Observed meteorological data supported climate analysis, CMIP6 downscaling, and SWAT+ simulations, while streamflow records (1990–2023) enabled hydrological calibration/validation. Three elasticity models (Budyko, Zhang, and Fu) then quantified climate sensitivity. SWAT+ calibration and validation achieved strong performance (R2 > 0.89, NSE > 0.85, KGE > 0.90, PBIAS < ±18%), accurately reproducing observed streamflow. Near-term projections show substantial baseflow increases (+57.5% under SSP2-4.5) and high groundwater recharge (up to 256.4 mm). Surface water yields rise under SSP1-2.6 and SSP2-4.5 but stabilize under SSP5-8.5 due to elevated evapotranspiration. By mid-century, baseflow moderates, while far-future SSP5-8.5 scenarios intensify runoff and flood potential. Elasticity analysis reveals higher sensitivity in the Fu model (0.212–0.260) than Budyko (0.106–0.130) and Zhang (0.0019–0.0065). The integrated SWAT + -elasticity framework provides a robust, scenario-dependent basis for adaptive management. We recommend prioritizing groundwater recharge strategies across all futures and developing specific infrastructure plans for high-flow extremes in the far future under SSP5-8.5.