Climate change impact on the hydrology of the Upper Apurimac Basin, Peru

ABSTRACT Graphical abstract showing SWAT modelling of the Upper Apurimac basin to assess CMIP6 climate scenarios and projected changes in evapotranspiration, water yield, streamflow, floods, and droughts. The Upper Apurimac River Basin (UARB), located in the southern Peruvian Andes, is highly vulnerable to climate variability and future water scarcity. This study assessed climate change impacts on streamflow (Q) and water yield (Wy) using the Soil and Water Assessment Tool (SWAT) hydrological model forced with five CMIP6 Global Climate Models (GCMs) under SSP245 and SSP585 scenarios. Climate projections were downscaled using the Delta Change method for the 2050s and 2080s. The calibrated SWAT model showed satisfactory to good performance in reproducing monthly streamflow during the 1981–2023 period. Results revealed spatially heterogeneous hydroclimatic trends, with significant increases in precipitation and Wy in the UA and A sub-basins, and a significant increase in Q only in the SR sub-basin. Future projections indicate temperature increases of up to 6 °C and precipitation changes from −13 to +72%, depending on scenario and time horizon. Hydrological responses show strong spatial and seasonal variability, with reductions in Wy and Q during dry months and substantial increases during the wet transition season. Under SSP585 by the 2080s, streamflow increases may exceed 90% in some regions. These findings highlight increasing hydrological variability and growing risks of droughts and extreme flows in the UARB.