Determination of Aquifer Parameters from Resistivity Data: A Case of University of Ilorin Campus, Northcentral Nigeria

Abstract

A total of twenty-one (21) vertical electrical sounding (VES) data were acquired using Pz-02 resistivity meter within the Precambrian basement area of part of Ilorin Metropolis north central Nigeria to evaluate the hydraulic characteristics of aquifers. The Schlumberger configuration with half-current electrode separation (AB/2) varying from 1 m to 60 m was used. The aquifer hydraulic characteristics such as hydraulic conductivity K and transmissivity T (Ωm2) were calculated from the interpreted VES data using the concept of Dar-Zarrouk parameters. The data, processed with computer software IPI2WIN, indicated three to four geo-electric layers, namely; topsoil, clayey (wet to dry), weathered or fractured basement and fresh basement with resistivity values ranging from 130 to 1469 Ωm, 52.6 to 8552 Ωm, 46.2 to 249 Ωm and 454 to 5022 Ωm, respectively. The depth to aquifer ranges between 6.17 m and 24.9 m and the overburden thickness ranges between 4.1 m and 22.7 m. The assessment of the materials above the aquifers showed that longitudinal conductance lies between 0.02 and 0.468 Ω–1, transmissivity values vary from 246 to 2419.8 Ωm2. The results obtained have offered worthwhile hydrologic information that will aid both exploration and exploitation of the groundwater system of the study area.

Keywords: Dar-Zarrouk parameters; aquifer; groundwater; VES; geoelectric layer