ASSESSMENT OF GROUNDWATER POTENTIAL USING GEOELECTRICAL METHODS IN BALOGUN AREA, IBADAN

Abstract

A geoelectrical survey involving Vertical Electrical Sounding has been carried out at Balogun, Ibadan, Southwestern Nigeria to delineate the aquifer units and evaluate the groundwater potential of the area. The area falls within the Precambrian basement of Southwestern Nigeria and predominantly underlain by Quartzite and quartz schist, undifferentiated gneisses/schists, and Augen gneiss. Ten (10) Vertical Electrical Sounding (VES) were conducted across the area using Schlumberger electrode configuration with a maximum half – current electrode separation of 100m with the aid of Allied Omega Resistivity meter. The acquired field data, after being plotted using Bi-log graph was processed and interpreted quantitatively by partial curve matching technique and computer iteration using WINRESIST Software. The interpreted VES result revealed the presence of five geologic sequences inferred as top soil, lateritic soil/ clay formation, Quartzite and quartz schist formation, weathered basement and fractured basement based on resistivity characteristics. Two probable aquiferous units; weathered and fractured basement having resistivity values ranging from 41-310 Ohm-m and 118 - 653Ohm-m respectively were delineated in the area. The weathered basement is mostly sandy with an average thickness of 26.5m making it capable of yielding appreciable amount of water to well while the fractured basement aquifer which is significant in enhancing groundwater discharge featured at depth range of 5.7m – 68.2m with 40% occurrences. The groundwater potential map produced upon integrating various kinds of aquifer maps using geoelectric parameters obtained categorized the area into low, moderate and high groundwater potential zones with about 70% of the area falling to moderate to good zones. Hence, sustainable groundwater development program is feasible in the community while finding permanent solution to the potable water scarcity in the areas well as for an improved basic amenity required of its residents particularly where both aquiferous units delineated exists.