Geo-electrical evaluation of groundwater potential at Peace-Land Estate, Magboro, Southwestern Nigeria

Abstract

Evaluation of groundwater aquifer distribution using electrical resistivity method was carried out within Magboro area of Ogun State to assess an alternative portable source of water for the populace in the region due to shortage of water supply. Twenty Vertical Electrical Sounding (VES) survey were carried out across the study area using the Schlumberger array configuration. Partial curve matching and computer iteration were used to quantitatively evaluate the data and generate the geoelectric sections using the WINRESIST software. The geoelectric sections generated from the resistivity results revealed four geoelectric stratum which are indicative of topsoil, sand, clay, and aquiferous sand. The topsoil thickness varies between 0.8 and 1.9 m with layer resistivity values that ranged from 99 to 666 Ωm. The second stratum consisted, of sand with resistivity values range of 100 - 185 Ωm and layer thickness values that varied between 8.5 to 12.7 m. The longitudinal conductance values of the topsoil range from 0.001 - 0.11 mhos at the study area. This is suggestive of poor protective capacity, thus the underlying sand is exposed to contamination from the surface. The third identified layer is indicative of clay materials with resistivity values ranged from 19 to 37 Ωm and layer thickness values that ranged between 18 to 50.5 m. This layer denotes the seal that could protect the underlying aquifer. The fourth horizon is presumably sand with resistivity values ranged from 104 to 231 Ωm. The overburden longitudinal conductance value at the third layer overlaying the aquifer units ranged between 0.9 - 2.10 mhos and mhos and are suggestive of a favourable assessment for protective capacity. Thus, the underlying aquifers units are safe from contaminant and could be considered suitable for probable groundwater development