Abstract

The study of the groundwater potential and aquifer protective capacity of over-burden units in Ado-Ekiti, Ekiti State, southwestern Nigeria have been undertaken. The area is underlain by the precambrian basement complex of southwestern Nigeria with local geology predominantly granite-gneiss and migmatite. 51 schlum-berger vertical electrical soundings (VES) were covered. The interpretation revealed three distinct geoelectric layers overlying the resistive basement, the topsoil, the weathered layer and the partially weathered/fractured basement. The depth to the top of basement (overburden thickness) varied from 1.0 to 74.8 m across the study area. Groundwater potential and overburden protective capacity maps were prepared. The former assisted in the categorisation of the area into high, medium and low groundwater potential zones. The clay content of the overburden was high, which informed the low groundwater potential rating but enhanced the overburden protective capacity. The characteristic longitudinal unit conductance (ranging from 0.004 to 2.11 mhos) of the area enabled the overburden protective capacity rating into good, moderate and weak. About 60% of the area falls within the good/moderate rating, suggesting a generally good overburden protective capacity around the study area.

Key words: Geoelectric, vertical electric sounding, longitudinal unit conductance, overburden protective capacity.