Application of Geoelectric Methods for Groundwater Depths in Igbogbo, Ikorodu, Lagos State, Nigeria

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This paper presents the result of the geophysical investigation carried out at Igbogbo Ikorodu, Lagos, Nigeria. The geophysical investigation was done using the Vertical Electrical Sounding (VES) and 2D electrical resistivity imaging techniques, with the aim of accessing the groundwater potential and delineate the subsurface layers of the study area. A total of twenty-four (24) VES were conducted at different points along four (4) traverses using Schlumberger electrode configuration with half-current electrode spread (AB/2) varying from 1 to 270 m. In the 2D electrical resistivity imaging, Wenner electrode configuration was adopted. Geoelectric sections made from the sounding curves revealed three geoelectric layers with resistivity values ranging from 53Ωm to 764 Ωm. These resistivity ranges were lithologically inferred to be topsoil, sand and sandy-clay, clayey-sand, dry-sand with corresponding Q, H and K – curve type. The first geoelectric layer represent the topsoil with resistivity values varying from 117 Ωm to 825 Ωm and thickness of 1.0 m to 2.0 m, the aquiferous unit was represented as the second geoelectric layer composed of sand with electrical resistivity values ranging from 130 Ωm to 238Ωm with thickness of 12.8 m to 30.7 m having a depth of 14.1 m to 31.8 m, while the third geoelectric layer represent sandy-clay, clayey-sand and dry-sand with resistivity values from 53 Ωm to 764 Ωm. The geophysical results shows that good aquifer unit is located in the sand layer of the study area with a depth range of 14.1 m to 31.8 m.