Hydrological responses of the Brahmaputra river basin using CMIP6 GCM projections for supporting climate resilient infrastructure design

The central northern region of Bangladesh has a low density and quality of sustainable rural infrastructures, and it is frequently affected by climate change-induced seasonal flooding and associated river erosion. This study used the Soil and Water Assessment Tool (SWAT) hydrological model to simulate future discharges under moderate and extreme Shared Socio-economic Pathway (SSP) scenarios, utilizing 13 bias-corrected Coupled Model Intercomparison Project Phase 6 (CMIP6) General Circulation Models (GCMs). Using these flow projections, the 1D HEC-RAS hydrodynamic model was then simulated to assess future water level fluctuations in six major rivers in the study region. The results indicate that the dry season will experience a more notable flow increase (up to 45%) than the wet season (up to 42%) compared to the baseline under the extreme scenario by 2100. The subsequent rises in water levels will also be significant in the major rivers in the Brahmaputra-Teesta River system. Based on these future water level changes, the study has prepared a guideline for building climate-resilient infrastructures in the study area.