The Nature of Aquifers in the Crystalline Basement Rocks of Ado-Ekiti, Igede-Ekiti and Igbara-Odo Areas, Southwestern Nigeria

Abstract

 Geoelectrical investigations (vertical electric sounding, VES) for groundwater in the basement rocks of Ado-Ekiti, Igede-Ekiti and Igbara-Odo areas, Southwestern Nigeria were carried out. Geophysical data revealed the area as the one that has undergone an irregular weathering front. The geoelectric curves at VES 1, VES 2 and VES 3 at Igbara-Odo were classified as HA, HAA and KH, respectively, while the two VES stations at Ado-Ekiti produced Q and KQH type curve. At Igede-Ekiti, the geoelectric curves obtained for the three VES stations were KH, KQHK and KHKH types. The VES stations were located in a migmatite-gneissic terrain at Igede-Ekiti, gneissic charnockite at Ado-Ekiti and in a granite-gneiss migmatite country rock at Igbara-Odo. Geoelectric lay- ers varied from 3 at Ado-Ekiti to 6 at Igede-Ekiti, with probed thicknesses of between 0.7 m to 151.9 m. The results of the processed data suggested that aquifers occurred both in the regolith and the fractured bedrock. In places, a regolith and the underlying saturated fractured bedrock might constitute the aquifers, having the promise of siting high yielding boreholes, such as at Igede-Ekiti and Igbara-Odo. However, thickness and recharge prob- lems made siting a borehole at Ado-Ekiti VES stations  undersirable.