Groundwater Exploration Using Electrical Resistivity Method: A Case Study of Ga-Gata, Ilorin, Nigeria

Twenty-five Schlumberger Vertical Electrical Soundings and six Horizontal Resistivity Profiling for groundwater exploration at Ga-Gata along Ajase-ipo road, Ilorin in Kwara State, Nigeria were carried out. The aim was to identify the different subsurface geoelectric layers and the aquifer units. Using the usual method of curve matching with the Orellana-Mooney Master curves and 1-D forward modeling with WinResist 1.0TM software, between three to five lithologic units were identified. These include: the topsoil, the lateritic layer, the weathered layer, the fractured layer and the fresh bedrock. The weathered and fractured basement constitutes the main aquifer unit. The depth to the bedrock varies from 0.8 to 46.1m. The geoelectrical interpretation of data obtained in this area has led to the delineation of a zone of low resistivity (0-400 ohm-m at AB/2 = 100m) which constitutes the major prospective zone in terms of high sustained yields of water. This work is significant as the area under study hosts two major institutions owned by the Federal Government of Nigeria with hundreds of people (staff and students) throughout the year. Groundwater provides drinking water entirely or in part for these institutions and majority of the water is used to satisfy their basic daily water needs. Scientific understanding and proper management of groundwater is therefore essential as it can alleviate problems if we seek its responsible use and replenishment. Therefore, there is an urgent need to focus on groundwater development given the fact that groundwater potential is high enough to sustain the domestic and reasonable agricultural supply in the study area.