ASSESSMENT OF GROUNDWATER POTENTIALS USING 2D ELECTRICAL RESISTIVITY AND RADIAL VERTICAL ELECTRICAL SOUNDING TECHNIQUE IN DUSTEN-KURA-MAITUMBI MINNA, NORTH- CENTRAL NIGERIA

Abstract

The availability of sufficient fractures are the main features that enhance the development of groundwater resources in crystalline rocks of the Basement Complex. In order to achieve a better understanding of the groundwater potential of the study area, geologic mapping was conducted first, followed by Radial Vertical Electrical Sounding (RVES). These were complimented with a 2D electrical resistivity tomography (ERT) surveyso as to provide sufficient information about the subsurface structures and lithology ofDusten-Kura-Maitumbiin Minna, north-central Nigeria. RVES was carried out in four different stations along two profiles using a portable Geo-Sensor resistivity meter.Electrical resistivity sounding data obtained were used to produce Vertical Electrical Sounding (VES) curves, basement resistivity mapand depth to basement map. Coefficient of anisotropy polygons were produced using RVES data. The 2D ERT survey covered three profiles of 100 meach designed to be orthogonal to the predominant structural orientation of the area. Geologic map show that the area is composed of amphibolite schist which have been intruded by porphyritic older granite rocks.The VES model curves reveal that the area is generally characterised by three geoelectric layers. Resistivities and depths of top soil layer range from 64 Ωm to 333 Ωm and 1.1 m to 4.2 m respectively. The middle layer consisting of slightly weathered rocks have resistivity values ranging from 15 Ωm to 781 Ωm and depths of 1.0 m to 4.2 m. Generally, the area has not undergone appreciable weathering which is evident from the depth to basement map which indicate shallow overburden. The degree of fracturing as indicated by the anisotropy polygons show that there is a decrease in fracturing with increasing depth.The results of the 2D ERT show strong correlation with interpreted VES and anisotropy polygons. However, conclusions drawn from the research suggest a low groundwater potential for the area.This research has shown that a combination of RVES and 2D ERT surveys are good complementary tools in delineating groundwater potential in a basement terrain.