Characterization of Groundwater Aquifers using Electrical Resistivity Tomography (ERT) in Some Parts of Rivers State, Nigeria

Abstract

This study is aimed at characterizing groundwater aquifers using electrical resistivity tomography (ERT) in parts of Rivers State, Nigeria. About five (5) vertical electrical soundings (VES) were conducted using the Schlumberger configuration, with current electrode spacing of 200m to 600m across different VES points. ABEM Tarrameter SAS 300B was used for earth probing and the data collected were analyzed using IP 12 WIN software. The results obtained reveled aquifer resistivities and thicknesses ranging from 7.667Ωm – 160,000Ωm and 0.331m – 35.1m respectively. The resistivity values obtained revealed the depth through which people of the area can obtain fresh water ranging from 35m to 50m, with adequate transmission rate. The hydraulic conductivity and transmissivity values obtained from the empirical equation range from 0.3274m/day – 606.314m/day and 0.212m2 /day – 514,919.84m2 /day respectively. The results show that VES 1 = 5 have a good hydrualic coductivity values greater than 5m/day indicating coarse sediments (sand/gravel), enabling efficient water transmission. The Isoresistivity, isopach, hydraulic conductivity and transmissivity maps were constructed using Surfer 29 software to show variation in resistivity and thicknesses across the VES points. The isoresistivity map at 10m revealed the resistivity range from 40 Ω𝑚 - 520 Ω𝑚, having a better aquifer for fresh water supply within the region. The second isoresistivity map at 50m revealed resistivity values ranging from 200Ω𝑚 – 2,600 Ω𝑚 indicating the presence of resistive materials within the study area. The isopach map of layer 1 shows coutour lines of equal thicknesses connecting different VES points , also indicates that the VES were positioned on a steep terrain.