Responses of streamflow extremes under solar radiation modification in the Muda River Basin, Malaysia

Study Region This study focuses on the Muda River Basin (MRB) in Malaysia, a tropical basin that is important for water supply and paddy irrigation in northern Peninsular Malaysia. Study Focus The impacts of Solar Radiation Modification (SRM) on tropical river basins remain largely underexplored. This study employed a calibrated SWAT + model driven by bias-corrected precipitation and temperature from GeoMIP6 projections under four scenarios, SSP2–4.5, SSP5–8.5, G6solar and G6sulfur, to evaluate the impacts of SRM on streamflow extremes and dry-wet abrupt alternation (DWAA) in the MRB. New Hydrological Insights for the Region Future hydrological responses are primarily characterised by intensified streamflow extremes and seasonal redistribution, while annual streamflow exhibits contrasting responses across climate scenarios. Streamflow generally decreases during the Northeast Monsoon and increases during the Southwest Monsoon. High-flow frequency and maximum streamflow are projected to increase under all scenarios, with the greatest increases under SSP5–8.5. Although SRM scenarios moderate changes in mean streamflow relative to SSP5–8.5, they do not consistently weaken hydrological extremes. Furthermore, DWAA analysis reveals relatively stable transition lags but considerable spatial variability in wet-phase intensity, with more abrupt post-drought responses projected in downstream areas. Overall, the SRM scenarios reflect complex, spatially heterogeneous hydrological responses in the MRB. Future research should consider different SRM deployment strategies and extend these assessments to include multi-hazard disaster risks and compound events.