Assessment of climate change impacts on rainfall, evapotranspiration, and streamflow in the Ribb Catchment, Ethiopia, using bias-corrected CMIP6 models

Diagram summarizing projected climate change impacts in the Ribb Catchment, including rising temperature and evapotranspiration, increased Kiremt flow, and reduced Belg and Bega streamflow. The Ribb Catchment, a key source for irrigation and the Ribb Dam in Ethiopia’s Upper Blue Nile Basin, faces critical water management challenges under climate change. Using three bias-corrected CMIP6 models under SSP245 and SSP585 scenarios, this study projects robust warming: maximum temperatures increase by 1.1–2.4 °C (SSP245) and 0.9–3.8 °C (SSP585) by 2100. Reference evapotranspiration rises up to 18%, driven by rising temperatures. Streamflow shows critical seasonal redistribution: Kiremt (main rainy season) runoff increases up to 11%, while Belg and Bega seasons decline sharply by 28%–34%. Despite projected annual rainfall increases, dry-season flows drop because higher temperatures amplify water loss through evapotranspiration before it contributes to runoff. These findings have direct implications: increased wet-season flows elevate flood risk and reservoir-filling challenges, while reduced dry-season flows threaten irrigation supply for the Fogera floodplain. This seasonal water imbalance necessitates re-evaluating current Ribb Dam operating rules and developing adaptive irrigation schedules to ensure food security. By quantifying uncertainty through a multimodel ensemble, this study provides a robust scientific baseline for climate-resilient water resource planning in data-sparse Ethiopian catchments, supporting long-term agricultural and hydrological stability.