Geoelectrical exploration for groundwater in crystalline basement rocks of Gbongudu community, Ibadan, Southwestern Nigeria

Abstract

Gbongudu community, Ibadan underlain by crystalline rocks of Basement Complex of Southwestern Nigeria has need for alternative water supply due to inadequacies of surface water supply and common occurrences of low yield or dry boreholes coupled with rapid development within the community. Geophysical investigation involving electrical resistivity was carried out with the aim of evaluating the groundwater potential of the community. Thirty-three (33) Vertical Electrical Soundings were acquired across the community adopting Schlumberger electrode configuration with current electrode separation (AB) varying from 2 to 200 m. The acquired field data were interpreted using partial curve matching with suitable auxiliary chart and "RESIST" resistivity sounding interpretation software was also used for iteration. The results revealed two to five geo-electric layers, namely, topsoil, clayey soil, lateritic clay, weathered layer, fractured unit and fresh basement. The weathered and the fractured units form the aquiferous zones in the area investigated. Thematic maps of geoelectric and Dar-Zarrouk parameters produced from the interpreted VES data are aquifer unit (weathered layer) thickness map, aquifer unit (weathered layer) resistivity map, overburden thickness map, basement resistivity map, basement topography map, reflection coefficient map, total longitudinal conductance map, total transverse resistance map and electrical anisotropy (coefficient of anisotropy) map. The thematic maps were combined to form a single component which gives the groundwater potential map of the study area. The groundwater potential map was used to classify the study area into poor, low and good aquifer potential zones. The study reveals that the weathered and fractured zone that occur in the southeastern part of the study area constitute the water bearing zone which can be regarded as good groundwater potential. This study has provided evidence on the hydrogeologic framework and subsurface nature of main aquifer units in the area.

Relating groundwater to geology in Sokoto basin, north-western Nigeria using multivariate and regression analysis: implications for groundwater availability

“…Since groundwater condition in this area is typical of the basement complex areas of Nigeria, there is no need for further analysis. [47][48][49][50]…”

Development of PROMETHEE-Entropy data mining model for groundwater potentiality modeling: a case study of multifaceted geologic settings in south-western Nigeria

“…Geophysical surveys are one of the most commonly used methodologies for evaluating groundwater potential zones since the conduit medium cannot be seen immediately on the earth's surface (Braga et al 2006). Several researchers have done groundwater hydrology studies, particularly in hard rock terrain, with promising results, including Omosuyi (2010), Mogaji et al (2014), Oladunjoye et al (2019), and Akintorinwa et al (2020).…”

Integration of GIS-based Multi-criteria Analysis Techniques for the Delineation of Groundwater Potential Zones in Oyo state, Nigeria using Bayes’ Approach

“…Nowadays, the use of geophysical and hydrogeological techniques such as resistivity sounding for groundwater exploration and water quality evaluations is also very common due to the simplicity of the technique and rapid advances in computer software and other numerical modelling techniques. Oladunjoye et al (2019) opined that the use of vertical electrical sounding technique for exploring groundwater resources overcomes the cost and time limitations (to a certain extent) and makes use of evaluation of electrical resistivity. Paine and Collins (2003) applied the use of airborne electromagnetic induction in groundwater salinization and resource studies.…”

“…Oladunjoye and Jekanyinfa (2016) worked on and improved Schlumberger area (Hummel -Schlumberger array) to obtain an improved result using Ibadan metropolis as a case study. The author opined that the Hamel-Schlumberger technique for exploring groundwater resources overcomes the limitations of using the conventional Schlumberger array and makes use of evaluation of electrical resistivity (Oladunjoye et al, 2019). Oladejo et al (2013) carried out a groundwater exploration study in Ogbomosho using Very Low Frequency (VLF) method.…”