Evaluating Impacts Of Climate Change On Water Availability: The Case Of Hargeisa Watershed In Somaliland

Abstract

The Hargeisa watershed is the lifeline water basin located in the Marodi-jeh region of Somaliland, which includes the capital city of Hargeisa. However, as a semi-arid and groundwater-dependent system, the watershed is highly vulnerable to the impacts of climate change. This study quantifies these impacts using the Soil and Water Assessment Tool plus (SWAT+) model, driven by downscaled data from three coupled model inter comparison project phase six (CMIP6) of Global Circulation Models (CanESM5, NorESM2-MM, GFDL-ESM4) under SSP2-4.5 and SSP5-8.5 scenarios. A regionalization approach using data from the gauged Dagahbur catchment was employed to overcome local data scarcity. Historical analysis (1995-2024) exposed a significant increasing trend in annual precipitation (up to 13.19 mm/year) alongside regional warming. Future projections indicate a complex hydrological response to accelerating warming, which could exceed +6.8°C by the end of the century under SSP5-8.5. Evapotranspiration is projected to increase substantially across all scenarios (+46.0% to +184.2%). Critically, despite this, groundwater recharge shows a consistent and significant increase, ranging from +4.1% to as high as +781.0%. Completely different, projections for surface runoff are highly uncertain, ranging from a decrease of -32.7% to an increase of +135.8%. This study concludes that while the Hargeisa watershed may see improved groundwater security, it faces a dual risk of increased droughts and heightened flood potential. These findings provide a quantitative basis for developing adaptive water management strategies to ensure the region's long-term water security.