Geophysical investigation of groundwater potential in parts of Afao Ekiti, Southwestern Nigeria

Abstract

A geophysical investigation was conducted to evaluate groundwater potential and explain anomalous water-table behaviour in hand-dug wells in a new community at Afao Ekiti during the 2023--2024 dry and wet seasons. The study used water-table measurements from ten observatory wells and Vertical Electrical Soundings (VES) data acquired along five traverses with the Schlumberger array. Electrode spacing (AB/2) varied from 1 to 100 m, and the maximum surveyed length was 200 m. Water tables were higher during the dry season than during the rainy season in eight wells, while two wells remained dry in both seasons. The interpreted VES results divided the area into two zones and revealed four lithologic units: topsoil, lateritic layer, weathered layer, and fractured or fresh basement. Two aquifer types were identified: a weathered-basement unconfined aquifer with resistivity values ranging between 50--150 Ωm. and a fractured-basement confined aquifer with resistivity values ranged between 100--250 Ωm. Groundwater potential is higher in Zone 1 than in Zone 2. Boreholes sited within Zone 1 are therefore expected to be productive and to yield groundwater sufficient for community needs.