Hydrogeological Studies for Groundwater Resource and its Vulnerability to Contamination in Owo, Southwestern Nigeria

Hydrogeological investigations were conducted at Rufus Giwa Polytechnic, Owo, Southwestern, Nigeria with the aim of evaluating the groundwater resource and vulnerability of the aquifers to contamination in the area. The geophysical survey involved Vertical Electrical Sounding (VES). The hydro-geological survey includes measurements of thickness of the vadose water, static water level determination, and hydraulic head in existing wells across the study area. A total of twenty seven (27) traverses were established in the studied area. The geoelectric section revealed 3 to 5 major layers comprising the topsoil, clay, laterite, weathered layer, partly weathered layer/fractured basement, and fresh basement rock. The Iso-resistivity map and isopach maps shows that the northeastern and southwestern parts of the institution show a high overburden thickness suggesting a high degree of weathering. Transverse unit resistance map shows that the northwest through the central to the southeastern part of the study area constitute the medium groundwater development areas, while the northeastern and southwestern parts are high groundwater development areas. The longitudinal unit conductance map shows low high L. U. C. values observed around southwestern and northeastern/eastern part of the area. The overburden protective capacity map shows a moderate protective at the southwestern and northeastern/eastern parts, while all other areas have poor/weak protective capacity. The static water level, water column and depth to water level vary between 316.9 m and 330.5 m, 1.3 m and 4.8 m, and 8.1 m and 10.5 m respectively. The average depth to the water level is about 9.4 m. This implies that the vadose zone is fairly thick, hence less vulnerable to contamination. Therefore considering the thickness of the vadose zone across the area, the resistivity parameters of the topsoil and the longitudinal conductance of the geomaterials, the southwestern and northeastern/eastern parts have would be fairly protected from contaminants arising from anthropogenic activities (moderate protective capacity) while other areas have poor/weak protective capacity