Assessing Streamflow Responses to Future Climate and Land Use and Land Cover Change in a Transitional Brazilian Basin Between Semiarid Dry Forest and Humid Tropical Forest Biomes

ABSTRACT Historically, severe drought events, coupled with land use and land cover changes, have significantly influenced streamflow behaviour This study enhances the understanding of these hydrological processes by assessing streamflow responses to future climate and land use and land cover change in a transitional Brazilian basin between semiarid and humid tropical forest biomes. Projections from 10 global climate models available through the Climate Change Dataset for Brazil (CLIMBra) were utilised incorporating bias correction via the Quantile Mapping method. Future land use and land cover changes were simulated using the land change modeller (LCM), while hydrological projections were generated through the soil and water assessment tool (SWAT), which was calibrated and validated with satisfactory performance, achieving coefficients of determination ( R 2 ) and Nash‐Sutcliffe (NSE) efficiencies in the ranges of 0.62–0.79 and 0.61–0.76 for calibration and 0.48–0.90 and 0.41–0.84 for validation, respectively. The results indicate a substantial expansion of agricultural and pasture areas, with a 280% increase over recent decades. Climate projections under the SSP2–4.5 and SSP5–8.5 scenarios show a progressive temperature rise and declining rainfall trends, with the SSP5–8.5 scenario exhibiting a steeper increase in temperature. Paradoxically, hydrological modelling suggests an intensification of streamflow extremes, with peak discharges ranging from 200 to 300 m 3 /s, particularly, in regions prone to extreme precipitation events. Notably, under SSP5–8.5, a more pronounced rise in flood peaks is observed, indicating elevated flood risks, even in moderate emissions scenarios. These findings underscore the necessity for adaptive water resource management strategies to mitigate future hydrological vulnerabilities in the basin.