Estimation of Spatial Distribution of Long-term Groundwater Recharge Variability over Ethiopia

Groundwater recharge is a critical component of sustainable water management, especially in Ethiopia, where rain-fed agriculture supports the livelihoods of most of the population. Despite its importance, comprehensive groundwater recharge estimates for the entire country remain limited, particularly given Ethiopia’s diverse climatic, topographic, and geological conditions. This study aims to evaluate the spatial distribution of long-term groundwater recharge across Ethiopia, focusing on the relationship between precipitation and total stream runoff and baseflow. The methodology integrates hydrograph separation techniques, regression models, and GIS-based analysis. Daily flow data from 139 gauging stations (1990–2010) were analyzed using a moving minima approach to separate baseflow from streamflow. Baseflow indices (BFI) were calculated, and regression models were developed to link mean long-term precipitation averaged over the catchment area to total runoff and baseflow across different geological and hydrological settings. Spatial variability was assessed using precipitation data from satellite-derived CHIRPS datasets, calibrated with ground-based observations. Additionally, relationships between BFI, geology, and topography were explored to understand the factors influencing recharge dynamics. The results reveal significant spatial variability in groundwater recharge, with regions of high precipitation and permeable geological formations exhibiting high baseflow contributions. Conversely, arid areas with impermeable substrates show weaker recharge and lower baseflow. The analysis demonstrates a strong correlation between precipitation and baseflow in favorable regions, highlighting precipitation as the primary driver of recharge, modulated by local geological and hydrological conditions. These findings underscore the importance of tailored, localized water management strategies for Ethiopia’s diverse hydrological conditions. They provide critical insights for improving water security, supporting sustainable groundwater utilization, and enhancing resilience in climate variability, particularly for the country’s rain-fed agricultural systems.

Key Words: Baseflow Index, groundwater Recharge, Long-term Precipitation, Ethiopia

 

Acknowledgments: This collaborative work is a part of the development aid project by the Czech Geological Survey No. ET-2023-006-RO-43040 (to K. Verner) entitled “Improving the quality of life by ensuring availability and sustainable management of water resources in Sidama Region and Gamo and Gofa Zones (Ethiopia)” financed by the Czech Republic through the Czech Development Agency.