Unlocking groundwater potential in the yirgacheffe catchment, main ethiopian rift region: A comprehensive analytic hierarchy process and geophysical approach

Abstract

Water is an invaluable resource, and the growing demand for groundwater driven by climate change, population growth, and evolving lifestyles presents significant challenges for ensuring sustainable water development and effective management. This study combines geological, geophysical, and Analytic Hierarchy Process methods to investigate groundwater resources in the Yirgacheffe Catchment in the Main Ethiopian Rift region. These resources are vital for local economies and domestic purposes. Due to drying wells, surface water pollution, and limited hydrogeological data, water scarcity is a concern. Electrical resistivity profiling with a Wenner array and WDA-1 meter across four 236-meter profiles was processed with Res2DinV software. Using an indicator-based weighting approach with nine key factors to assess groundwater potential, the identified zones were validated through comparison with water point data and geophysical results. The geophysical analysis identified three subsurface layers: (1) a dense rhyolite ignimbrite and basalt layer with high resistivity (>2000 Ωm), (2) a weathered zone with moderate resistivity (200 – 2000 Ωm), and (3) a shallow topsoil and clay layer with low resistivity (4 – 200 Ωm). These findings show variations in rock integrity and weathering, affecting groundwater flow and construction stability. The groundwater potential map was validated with a Receiver Operating Characteristic (ROC) curve (76.6 %), revealing five groundwater potential levels: very low (12.96 %), low (28.23 %), moderate (28.91 %), high (19.82 %), and very high (10.08 %). Areas with moderate to very high potential are key for sustainable development and management. Sensitivity analysis of the Aquifer potential map revealed that lithology, elevation, and lineament are the most influential factors affecting groundwater potential. The findings of this research provide a reliable tool for decision-makers to improve groundwater resource development and management, plan for new well drilling, and adopt effective groundwater protection strategies, particularly in Yirga Cheffe town and its surroundings. Furthermore, the methodology applied in this study can be adopted in regions with similar hydrogeological settings.