Hydrogeophysical Investigation for Groundwater Development in the Crystalline Terrain of Ohaganyi Area of Lokoja, North-Central, Nigeria

Hydrogeophysical investigation of Ohagainyi area of Lokoja was undertaken to understand the local geology, ground water conditions and the prospect of groundwater development in the survey area. In this study, 2D Electrical Resistivity Profiling was carried out using electrical resistivity measurements methods. Wenner electrode configuration was employed to determine the hydrogeological characteristics of the survey area. Consequently, Five Vertical Electrical Sounding (VES) points were selected based on the 2D Profiling results employing the Schlumberger electrode configuration with maximum half-current electrode spread ranging from 70 m to 100 m; the half-potential electrode spread range from 0.3 m to 5 m. Four layers were identified by the VES: topsoil, weathered, fractured, and the fresh bedrock. The weathered/fractured geologic units are the two aquifer types that were identified from the VES results. The H-type curve demonstrates that the resistivity of the first layer is higher than that of the second layer and lower than that of the third layer (ρ1 > ρ2 < ρ3s). The first layer is made up of clay and laterite. The weathered basement aquifer formed the second layer with thickness ranges of 0.69 m − 6.12 m. and the resistivity range of 3.84 Ώm − 35.17 Ώm. The fractured aquiferous layer underlain the (WB) zone with thickness range of 8.44 m – 50.7m and resistivity values ranges from 429.6 Ώm -21726.6 Ώm. If the density of the fractures in the fractured column is high, the groundwater yield from this type of aquifer could be high. The final layer is the fresh basement, which has resistivity values ranging from 16.22 Ώm to 41790.1 Ώm.