Impact of climate change on blue and green water availability using bias corrected CMIP6 ensemble and SWAT models at Keleta catchment, Awash basin, Ethiopia

ABSTRACT Workflow showing CMIP6 data bias correction, SWAT modeling, and projected changes in blue and green water in the Keleta Catchment. Understanding the response of blue and green water resources to climate change is essential for sustainable water management. This study assessed the impacts of climate change on projected blue and green water availability in the Keleta catchment, using bias-corrected CMIP6 climate models and the SWAT hydrological model. The bias corrected ensemble means were used as inputs for hydrological simulation under two shared socioeconomic pathways (SSP2–4.5 and SSP5–8.5) scenarios. The SWAT model calibration and validation showed satisfactory performance (R2 = 0.79, NSE = 0.78) for simulating streamflow. The results showed green water consistently increase, whereas blue water is projected to decline under both scenarios, except in the 2050 and 2080 s under the SSP5 scenario relative to the historical average. Mean annual precipitation is projected to increase by 3.7–13.4% under SSP2 and by 6.3–38.1% under SSP5 in the catchment. Both green and blue water showed an increasing trend under both scenarios, with Sen's slope of 4.2 and 11.1 mm per decade under SSP2 and 12.5 and 40.8 mm per decade under SSP5, respectively. Generally, there is intensified hydrological responses and increased water availability under future climate conditions. However, the decrease in blue water availability under SSP2 indicates the need for adaptation strategies to enhance climate resilience, while flood management under SSP5, especially in the 2080s.