Historical trends and future changes in hydroclimate extremes using CMIP6 and SWAT + in the Awash Basin and Mojo catchment, Ethiopia

The Awash basin in Ethiopia faces severe water insecurity driven by high climate variability, recurrent droughts and floods, and rising water demand—conditions projected to intensify under climate change. This study examines historical (1981–2010) and future (2020s, 2050s, 2080s) hydroclimatic changes under SSP2-4.5 and SSP5-8.5 scenarios, focusing on precipitation, temperature, streamflow, drought, and flood dynamics, with detailed analysis for the Mojo catchment. Outputs from seven top-performing CMIP6 GCMs were bias-corrected using quantile mapping for precipitation and variance scaling for temperature. The Soil and Water Assessment Tool Plus (SWAT+) hydrological model is used to simulate streamflow across Mojo catchment in Awash basin. Results reveal strong spatial contrasts in precipitation trends. During March–May (MAM), the Upper Awash basin shows minimal PRCPTOT change (< 2 mm), slight increases in CDD, and declines in wet-day frequency and extreme rainfall. The Middle Awash basin exhibits reduced PRCPTOT and CWD but higher CDD (+ 1–4 days), while the Lower Awash basin shows marked increases in CDD and 2023decreases in CWD. In June–September (JAS), PRCPTOT rises in the Upper basin (+ 12 mm) but declines in the Middle (− 24 mm) and Lower basins. Future projections indicate increased MAM rainfall in the Upper and Lower basins (up to + 50% in Afar lowlands) but declines in the Middle basin. CWD is projected to rise across the basin, while extreme rainfall (R99pTOT, Rx5day) intensifies in the Upper basin (+ 70% by the 2080s). In the Mojo catchment, streamflow decreases by 80–100% in MAM but increases up to 70% in July–August. Projected temperature rises (+ 2.0 °C max, + 1.9 °C min), along with higher flood frequency (+ 48%) and drought severity (+ 36%), highlight the urgent need for climate-resilient integrated water resource management in the Awash basin.