This study was carried out to explore for groundwater at the proposed site for the senate building of Olabisi Onabanjo University, Ago-Iwoye, Nigeria, using a 3D Electrical Resistivity Survey to identify subsurface aquiferous layers capable of hosting groundwater and the presence of secondary geological structures such as fracture, joint, etc., capable of favouring groundwater movement beneath the earth surface. Nine (9) -2D profiles with a length of 100m were established parallel with a distance spacing of 5m apart from one another using the Dipole-dipole electrode array configuration. The recorded resistance value was multiplied by the appropriate geometric factor to obtain the apparent resistivity values which were later structured to form a 3D grid outline using the ZONDRES3D software to produce the structural resistivity subsurface image via forward modeling and inversion. The interpretation of the image generated in relation to geological inference revealed that the subsurface is underlined with a clayey layer, sandy-clay formation, sandy weathered layer, and fresh basement with resistivity values varying (32Ωm-100Ωm, 101Ωm-300Ωm, 301Ωm-700Ωm and >700Ωm respectively) at different depths of occurrence geospatially. The study delineated the sandy weathered zone as the aquiferous zone because of its ability to store and transmit water at a reasonable rate. The most prominent area with the relatively thick sandy weathered unit is found toward the south-eastern flank up to a depth of 25m and has been earmarked for any groundwater exploitation project. The study has demonstrated the efficiency of using electrical resistivity in imaging the subsurface from which subsurface structures that influence the occurrence of groundwater beneath the earth surface may be interpreted.
Key words: Groundwater, Lithology, Electrical, Subsurface, Resistivity
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