Geophysical investigation of groundwater potential in Iwo, Osun State, Southwestern Nigeria using audiomagnetotelluric method

Abstract

This research emphasizes the significance of groundwater for human activities and the challenges of prospecting in complex basement terrain. The study suggests using the Audiomagnetotelluric (AMT) method to explore the subsurface conductivity structure as an indicator of potential groundwater resources. The AMT method, preferred for its deep penetration and sensitivity to resistivity changes, is analyzed using the Audiomagnetotelluric Data Management Tool (ADMT) software for data interpretation. The research demonstrates the effectiveness of AMT in mapping groundwater and characterizing geological materials up to a depth of 200 m.The analysis reveals distinct layers with varying resistivity values, primarily composed of Pegmatite and Migmatite gneiss. Pegmatite, with its lower resistivity, acts as a water-bearing zone when weathered, while Migmatite gneiss's higher resistivity suggests reliance on fracture zones within the bedrock for groundwater exploration. Shallow potential groundwater zones are identified at 10–30 m depth in certain profiles, while deeper zones are detected at 40 m and beyond across the study area. The prevailing aquifer systems are influenced by fractures and weathered zones. The saprock region, located between fresh bedrock and regolith at 40 m depth and above, is deemed most promising for drilling purposes. Overall, this study underscores the effectiveness of the Audiomagnetotelluric technique in delineating zones with high groundwater potential. The research concludes that combining the AMT method with ADMT software provides valuable tools for groundwater prospecting in complex basement terrain, offering detailed data on the subsurface resistivity structure and facilitating the identification of potential groundwater resources.