Modeling climate change impacts on streamflow dynamics in the Melka Wakana catchment, Ethiopia

ABSTRACT Schematic overview linking CMIP6 climate projections with SWAT modeling to assess hydroclimate impacts on streamflow in the Melka Wakena catchment. Streamflow in semi-arid regions, the Melka Wakana River in southeastern Ethiopia, is highly vulnerable to climate change; yet hydrological assessment remains limited due to data scarcity and ungauged basin outlets. This study integrates the Soil and Water Assessment Tool (SWAT) with bias-corrected multi-model ensemble projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to assess streamflow dynamics using spatiotemporal hydrometeorological and climate datasets. The CMIP6 projects relatively stable mean annual precipitation during mid-century, followed by substantial declines by late-century under both SSP2-4.5 and SSP5-8.5 scenarios. In contrast, annual maximum and minimum temperatures are projected to increase consistently, with stronger warming under SSP5-8.5. Under SSP5-8.5 (2040–2069), the mean flow is projected to decrease by 27%, accompanied by reduced seasonal variability and an increased probability of low flows (about 17%). Paradoxically, monthly scale flows are expected to increase under SSP2-4.5 (2040–2069), likely due to enhanced orographic rainfall. Overall, late-century projections under high-emission pathways indicate flattened flow seasonality, prolonged dry season, and heightened hydrological drought risks. These findings highlight increasing water scarcity, soil moisture depletion, and seasonal hydrological redistribution, underscoring the need for proactive, climate-adaptive water resource management in the Melka Wakana River.