Electrical resistivity and magnetotelluric integration for groundwater exploration at the proposed central library in Achievers University Owo, Nigeria

Effective groundwater resource management in crystalline basement terrains requires accurate delineation of aquifer zones using high-resolution subsurface imaging. Conventional geophysical methods for groundwater exploration often face depth limitations, which hinder comprehensive groundwater assessment. This study integrates Vertical Electrical Sounding (VES), Electrical Resistivity Tomography (ERT), and Audio-Magnetotelluric (AMT) methods to investigate groundwater potential at the proposed central library site of Achievers University, Owo, Nigeria. The objective was to overcome the depth limitations of conventional methods and improve subsurface resolution by combining the complementary strengths of the three methods. Three traverses of 50 m each were established, each containing two VES points, totaling six soundings. VES data revealed four lithological units like topsoil, lateritic/quartzite formation, weathered bedrock, and fractured bedrock indicating aquifer zones at depths greater than 25 m. Identified curve types (QQ, KH, HK, QH and KQ) were indicative of groundwater presence though with QQ and KQ requiring caution due to the possibility of less permeable formation. ERT results further delineated potential aquifer at depths of 30–50 m in traverses 1 and 3, and below 30 m in traverse 2. AMT survey extended the depth of investigation, revealing deeper aquifer systems between 60 and 100 m across all traverses. The integration of these geophysical methods provided a more comprehensive understanding of the subsurface, combining the high near-surface resolution of VES and ERT with the deep penetration capability of AMT. The findings validate the presence the presence of both shallow and deep-seated aquifers and highlight the suitability of AMT in crystalline basement terrains. The study recommends the adoption of integrated geophysical methods for improved groundwater exploration and sustainable resource management in similar geological settings.