Application of Geoelectric Survey for Delineating Groundwater Recharge Zones for Drilling Standard Water Wells in Owerri North Area, Nigeria

Vertical Electrical Soundings (VES) technique was adopted to map the groundwater flow pattern in Owerri North in order to delineate recharge zones. Twenty VES stations were sited in different communities. Field data was acquired using Omega-500 resistivity meter and processed with Advanced Geosciences Incorporation (AGI) 1D resistivity inversion software. At each VES station, the global positioning system (GPS) was used to measure the coordinates and elevation. Five of the stations were sited near existing boreholes to enhance interpretation. The modelled results revealed multi-geoelectric layers, with the aquifer layers composed mainly of sands and sandstone. Using the ground elevation and water table values, the hydraulic head for the aquifers were obtained. Aquifer resistivity varied from 0.1Ωm determined at Naze (VES 11) to 1208.5Ωm obtained at Azaraegbelu (VES 18). Depth to water table also varied across the study area with values ranging from 8.5m at ChukwumaNwoha (VES 3) to 67.07m determined at Orie Uratta. The aquifer hydraulic head varied from the value of 7.84m recorded at shoprite egbu (VES 19) to 81.50m observed at ChukwumaNwoha. The hydraulic head map shows the drainage pattern of the groundwater from which the recharge zones were delineated. The flow direction is from areas of high hydraulic head to areas of low hydraulic head. Two recharge zones corresponding to high groundwater potential areas for siting standard wells were identified. The results of this study have obvious implications in planning and construction of proper surface drainage to reduce flooding in Owerri urban and environs