Climate change impacts on hydrology and socio-environmental exposure across the Amazon Basin

Abstract Climate change is altering hydrological regimes across the Amazon Basin, with implications for water security, freshwater ecosystems, and climate adaptation planning. This study analyzes projected multiannual and seasonal streamflow changes for 2015–2050 under SSP3-7.0 and SSP5-8.5 using HydroBID, building on a previously calibrated and validated Amazon Basin model implementation. New simulations were generated using bias-corrected and downscaled climate forcing from an ensemble of five global climate models, and hydroclimatic indicators were summarized across 138 hydrometric reference points distributed throughout the basin. Projected changes were spatially integrated with socio-environmental datasets, including population, Indigenous territories, protected areas, fisheries, agriculture, livestock, and hydropower infrastructure, to identify areas of potential exposure. Results indicate widespread declines in mean annual streamflow, typically ranging from 10 to 30%, with localized increases in some Andean headwaters. Seasonal analyses show that the strongest reductions occur during the dry season, reinforcing concerns regarding seasonal water stress and exposure of water dependent systems. The study further links projected hydrological changes with Nature-based Solutions relevant landscape categories, including protection of intact landscapes, agricultural management, pastureland management, and floodplain restoration. By combining projected streamflow changes, socio-environmental exposure, and NbS relevant spatial priorities, the analysis provides a basin-scale, spatially explicit basis for identifying regions where climate driven hydrological shifts may intersect with existing pressures and adaptation opportunities across the Amazon Basin.