Assessment of Groundwater Potential and Aquifer Characteristics using Inverted Resistivity and Pumping Test Data within Lokoja Area, North-central Nigeria

Abstract

Kizito O. Musa*, Jamilu B. Ahmed^*, Fabian A. Akpah, Ernest O. Akudo, Ikenna A. Obasi, Solomon S. Jatto, Andrew C. Nanfa, Jacob B. Jimoh

Aquifer potential were evaluated within Lokoja and environs with the aim of estimating their hydraulic parameters from resistivity and pumping test data. Twenty-six (26) vertical electrical sounding (VES) and eight (8) pumping test data were obtained and utilized for this purpose. The results of the analysis indicate that the area is underlain by five (5) geoelectric sections which have been interpreted as the topsoil, lateritic clay, sandy-clay/weathered/ fractured basement complex rocks (aquiferous units), and clay/fresh basement complex rocks for the sedimentary and basement portions respectively. The resistivity and thickness of these lithologic units are; the topsoil (10.8 – 407.7 Ωm; 0.7 –17.5 m), lateritic clay (1.1 – 1488.5 Ωm; 2.2 – 42.0 m), sandy-clay/weathered/ fractured basement (10.4 – 3,595.6 Ωm; 5.2 – 82.6 m), clay/fresh basement (3.2 – 3,844.2 Ωm; 4.5 – 23.4 m). The resistivity of the aquifer zone indicates that the southeastern to the northwestern portion of the study area has higher groundwater potential than the other portions. The aquifer thickness is higher in the southern portion compared to the rest of the study area. Depth to the aquifer is higher in the northern and parts of the southern portions. Transmissivity (7.605 – 721.648 m²/day) and permeability (0.423 – 45.103 m/day) values support the view that the southeastern portion is most prolific for groundwater exploration in the study area. The Longitudinal conductance (0.013 – 1.600 mho-m), and the transverse resistance (119.0 – 29,710.7 Ωm²) values suggest that the area has a poor – good vulnerability index. The fracture contrast (0.040-22.430) and reflection coefficient (-0.902-0.915) indicate that the water-filled fractures occur mostly in the southern part of the study area. The study highlighted the efficacy of the VES data in estimating aquifer hydraulic parameters and hence is recommended in areas with no available pumping test data.