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Research Paper | Geosciences and Environment | Nigeria | Volume 12 Issue 9, September 2023
Geo-Electric Soundings and Electrical Resistivity Tomography for Mapping Fractured Crystalline Rock Aquifers at Emure-Ile, Owo, Southwestern Nigeria
Olanegan Paul Oluwasegun | Fasunla Olukayode Michael
Abstract: The combination of geoelectric soundings and electrical resistivity tomography (ERT) in groundwater exploration has been employed at Bolorunduro Quarters, Emure-ile south, Owo, Ondo State, Nigeria for delineating the subsurface layers, determining the geo-electrical characteristics to identify geological structures such as faults, weathered/fractured basement that are favorable to groundwater accumulation and transmission; an area with reported number of failed water wells and borehole drilling attempts. Forty-nine Vertical Electrical Soundings (VES) were conducted to assess the primary geoelectric parameters and secondary Dar-Zarrouk parameters for estimating the groundwater potential of the area. The VES surveys identified four geo-electric subsurface layers namely; topsoil, partially weathered/subsoil layer, highly weathered/fractured basement, and fresh basement. Based on the overburden thickness, hydraulic conductivity and aquifer transmissivity, the study area was delineated into low, moderate, high and very high groundwater potential zones. Two-dimensional electrical resistivity tomography was also conducted along four profile lines (each of length 300m) for imaging the VES delineated-low potential area for possible deep fractured basement columns. As a result, a fault/fracture line was identified across profile lines 1, 2 and 3 which is indicative of deep seated fracture zone apparently not detected by the VES owing to suppression overlying high resistivity layers. This fracture zone occurrence was verified with two confirmatory VES 50 and 51 and lithologic profile from a well and a borehole in the proximity of the 2D anomalies mapped by the ERT.
Keywords: Electrical Resistivity Tomography (ERT), Geo-electric sounding, Fracture, Crystalline rock Aquifer, Dar-Zarrouk Parameters
Edition: Volume 12 Issue 9, September 2023,
Pages: 1104 - 1115