Groundwater Prospecting Using Combined Vertical Electrical Sounding and Borehole
1Oyegoke, S. O., 2Adebanjo, A. S., 3Fayomi, O. O. and 4Obot, O.
1,2,3,4Department of Civil Engineering, Afe Babalola University Ado-Ekiti. Ekiti State, Nigeria.
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This study aimed to determine the prospect of groundwater in Afe Babalola University, Ado-Ekiti(ABUAD); result of which will inform of the possibility of getting sufficient water underground. Geophysical survey was carried out in the study area and complemented with performance of an existing borehole. The survey involved 1-D Vertical Electrical Sounding (VES) utilizing the Schlumberger electrode array with half-current electrode separation (AB/2) that ranged from 1m to 50m. The VES data interpretation involved partial curve matching and computer assisted 1-D forward modeling using IPI 2 WIN software. The results showed the subsurface to have 3-layer earth strata comprising of sandy-clay top soil up to 3.26m deep, weathered/fractured basement in the next 9.06m depth and then, the fresh basement with the weathered layer constituting the main aquifer unit. The resistivity values of the weathered and fractured basement are 174 and 192 ohmm indicating relatively low potential for groundwater resource. Pumping test on a nearby borehole gave specific capacity of 7.95m2/day which depicts a low to intermediate transmissivity conforming to the VES.
Keywords: ABUAD, transmissivity, groundwater, resistivity, basement, VES.