An integrated geophysical approach to groundwater potential assessment in Central Ethiopia: Adama to Awash Melkasa areas

Abstract

<h2>Abstract</h2> Water is an essential requirement for the existence of human beings and other forms of life. In Ethiopia, it is a crucial resource for addressing the rising demand of water to support agricultural, and domestic needs. The properties of aquifers and the associated geological structures, significantly influence the potential of groundwater in any hydrogeological settings. This study aims to investigate the groundwater potential of the volcanic aquifer in central Ethiopia, focusing on the regions from Southern Adama to Awash Melkasa, by employing integrated electrical resistivity, and magnetic methods. The study utilized 12 vertical electrical soundings (VES), and 276 magnetic data points to achieve its objectives. Various curve types were observed from the field electrical resistivity log-log plots including AHK, KHK, HKH, AKH, KHKH, and HAKH types, with the KHKH curve being the most dominant, followed by KHK curve type. Geoelectric sections revealed four to six layers, with highly weathered and fractured basalts, and ignimbrites identified as the primary aquifers in the area; aquifer thicknesses varied from 50 to 149 m. Dar Zarrouk parameters computed from inverted true resistivity, and thickness values reveal hydraulic conductivity values ranging from 7.64 to 40.58 m/day, with an average of 14.28 m/day, and transmissivity values ranging from 115.08 to 3547.58 m²/day, with an average of 1109.55 m²/day. The analysis of analytic signal and tilt derivative maps of magnetic data, along with 2D modeling, reveals various geological structures. Lineaments were extracted using tilt derivative analysis, revealing dominant trends of NNE–SSW, NW–SE, and N–S in the study area. These structural features enhance potential for groundwater in the study area. Integration of electrical sounding data, analysis of Dar Zarrouk parameters, and magnetic data is an indication that a high potential for groundwater was found in the central to southern parts of the study area.