The Application of Vertical Electrical Sounding for the Geophysical and Hydrogeological Investigation in University of Benin Area, Nigeria

Abstract

The occurrence and distribution of groundwater in a sedimentary basin are localized and confined to the weathered sandy layer/zone. The study was carried out with the aim of demonstrating the vertical electrical sounding method of investigation in the exploration of groundwater at the University of Benin, around VC’s lodge. A total of six VES points were probed using the ABEM SAS 300C terrameter which was used to generate field data applying the Schlumberger Array with AB/2 of 1.5 m, 215 m. The results were simulated using IPI2WIN software. The results show an average of four geo-electric layers per VES point; superficial layer, duricrust, clay layer, alluvium, sand layer and the weathered sandy layer. For VES 1-6, the thicknesses of the water table are 11.6 m. 16.6 m, 22.5m, 30.5 m 51.4 m and 27.8 m respectively and the depth to the water table is 124.4 m, 124.6 m, 78.4m, 55.2 m, 38.5 m, and 29.4 m accordingly. Going by the results, VES 1 & 5 ranked the highest water prospect due to the thickness of the water table layer, the depth to the water table and most importantly the weathered/fractured layers with resistivity as high as 15,188 Ω and 76,432 Ω for VES 1 & 5 respectively, which also increases the permeability and storage of the groundwater. VES 2, 3, 4, and 6 are also wet reservoirs but for their shallow thicknesses and depth to the water table which will influence the purity of the water. However, further investigation is needed to ascertain the suitability of the water as portable drinking water by examining the physicochemical and hydrogeological characteristics of the existing Boreholes drilled in the vicinity of the study area. The findings of this study are a reminder of the essence of a geophysical survey prior to drilling exercises and the suitability of electrical resistivity as a tool for aquifer delineation.