Investigation of Groundwater Potential Zones Using Integrated Geophysical Techniques at Apaken Area, Sagamu, Southwestern Nigeria

Groundwater potential zones in Apaken Sagamu, South Western Nigeria was investigated using electrical resistivity and the natural electric field combined approaches. Twelve VES stations and six 2D electrical resistivity tomography (ERT) profiles were probed utilizing Schlumberger and Wenner array modes. respectively. The VES and 2D ERT data were processed and inverted using partial curve matching/WINRESIST and RES2DINV softwares, respectively. Natural electric field (NEF) technique was also employed on the traverses using PQWT. Three to five geo-electric layers are revealed by the results of the interpretation of the VES data: the topsoil, which has resistivity values between 55.5 and 747.3 Ωm and thicknesses between 0.4 and 2.9 m; laterite soil layer, which has resistivity values between 225.6 and 8985.8 Ωm and thicknesses between 0.8 and 18.3 m; sandy clay layer, which has resistivity values between 504.3 and 5477.8 Ωm and thicknesses between 6.5 and 34.6 m; and the layer of ferruginous medium to coarse sand, which has resistivity values between 603 and 4422.8 Ωm. The overburden thickness ranges from 1.2 to 24.0 m. Ferruginous fine sand layer of the VES stations constitutes the main aquifers’ zone. Based on reflection coefficient and overburden thickness values used to infer groundwater yield status, 50% of total VES points had moderate to high groundwater yield whereas the remaining 50% exhibit very low to low groundwater potential. According to longitudinal conductance values of the overburden units, two marked aquifer protecting capability zones were pinpointed: the poor (91.67%) and weak (8.33%). The identified moderate to high groundwater yield zones (VES stations 4, 6 and 11) with their associated moderate protective capability were located on the west and northwest sides of the study area, and thus suggested for drilling. The result of 2D resistivity and NEF concur at traverses 3 and 4 indicating good yield of groundwater zones.