APPLICATION OF 2-DIMENSIONAL ELECTRICAL RESISTIVITY TOMOGRAPHY AND VERTICAL ELECTRICAL SOUNDING IN AQUIFER VULNERABILITY ASSESSMENT IN ABAK, SOUTHERN NIGERIA
2-Dimensional Electrical Resistivity Tomography (ERT) and Vertical Electrical Sounding (VES) were used to study the vulnerability of aquiferious zone in Abak, Southern Nigeria. A total of 10 ERT and 10 VES soundings were carried out. The Werner electrode configuration was employed for ERT data acquisition, while the Schlumberger electrode configuration was used for VES data acquisition. The data were collected using a SSP-ATS-MRP model resistivity meter. The ERT data was analysed using RES2DINV software, while the VES data was modelled using WINRESIST software. Three to four geoelectric units (laterite topsoil, medium-grained sand, coarse-grained sand, and sandy clay sand) were identified in the area. The aquifer thickness in the area ranged from 24.2 m to 43.7 m, with an average value of 33.45 m. The area has very small overburden layer above the aquiferious zone (0.6 to 13.9 m), hence it may not provide sufficient protection against infiltration of contaminants from the overlying layers. Longitudinal conductance varied from 0.0053 Ω-1 to 0.1025 Ω-1, with an average value of 0.020 Ω-1. This value is less than 0.1 Ω-1, indicating the aquifer in the study area is situated within zones of poor protective capacity and therefore vulnerable to surface contaminations.
KeyWords: Aquifer, electrical resistivity, longitudinal conductance, electrical resistivity tomography, aquifer vulnerability.
