Geoelectrical evaluation of groundwater potentials of Bwari basement area, Central Nigeria

An investigation has been made of the groundwater potentials of Bwari basement area using solely geoelectric surveys. Twenty vertical electrical soundings along different transverses were conducted with maximum electrode spacing of 300 m. The results revealed that the area is characterized with 3 to 6 geoelectric subsurface layers with variability in resistivities and thicknesses of the different layers. The overburden thickness ranged from 6.9 to 72.9 m, with thinnest and thickest overburden observed at the central and western areas respectively. Dar Zarouk parameters (transverse resistance and coefficient of anisotropy), reflection coefficient, resistivity contrast, weathered layer thickness and overburden thickness were used as indices for evaluation of groundwater potentials. The area’s groundwater productivity potential was hence, classified into two zones namely; high and low. This study has revealed that no single factor (index) determines the groundwater productivity potential but a combination of two or more factors. For example, not all the areas with thick overburden or high weathered layer thickness correspond to high groundwater potential.   Key words: Groundwater potential, electrical resistivity, transverse resistance, coefficient of anisotropy, Bwari.