Evaluation of Groundwater Potential of Crystalline Basement Area of Kogi State Polytechnic, Osara Campus, North-Central Nigeria using Electrical Resistivity Method

Abstract

Hydrogeophysical study was carried out in the Basement Complex area of Kogi State Polytechnic, Osara Campus, to investigate the groundwater potential of the subsurface layers. Acute water shortage and challenges of abortive and non-functional open and closed wells has prompted this study on the development of the groundwater resources. This work involves using the electrical resistivity method to investigate concealed fractures within the area with the aim of delineating near surface/subsurface geological layers to determine the depths, thickness, structural trends and spatial distribution of basement rocks as potential sources of groundwater.  A total of thirty six vertical electrical sounding (VES) using the Schlumberger configuration was employed for the study. The depth and resistivity of the subsurface layers were determined.  The interpreted results of the geo electrical sections indicates the presence of four subsurface layers: top soil of thickness and resistivity values ranging from 0.2 – 5.0m and 169 – 3728 ohms meter, weathered basement ranging from 5 – 12m and 100 – 914 ohms meter, fractured basement ranging from 6.2 – 196 meters and 42 - 196 ohms meter the fresh rock bedrock ranging from infinity in thickness and 741 – 3691 ohms metres.  Geo electric sections, overburden Isopach maps of the area were drawn with basement depressions and elevations, the basement depressions are the priority areas for groundwater abstraction within the study area. Keywords: Osara, Groundwater, Electrical Resistivity, Fracture, Geoelectrical sections