Groundwater potential evaluation in parts of Southwestern Nigeria using Dar-Zarouk parameters

Abstract

Dar-Zarouk parameters namely longitudinal conductance, transverse unit resistance, longitudinal resistivity, traverse resistivity, and coefficient of anisotropy, derived from electrical resistivity soundings,were employed in the western and south western portions of Sheet 223 Ilorin NW, Southwestern Nigeria to evaluate the subsurface water prospect. This is aimed at determining the potentiality and vulnerability of groundwater in the area.The longitudinal conductance values obtained range from 0.027 S at VES 3 in the north, indicating the poorest protective capacity, to 26440.95 S at VES 157 in the south, indicating the highest protectivity. Thus, the protective capacity rating of the study area shows very poorly, weak, moderate, good, and excellent ratings at VES stations 10, 12, 9, 2, and 178 respectively.The total transverse resistance range is 8.6 - 32733.87 Ωm², with the lowest at VES 206 in the southeastern part, indicating high prospects, and the highest at VES 47 in the northern part of the area, indicating poor prospect.The lowest longitudinal resistivity (0.1951 Ωm), indicating high potential as well, occurs at the southern part and while the highest value of 8095.63 Ωm is obtained at the northern part.Furthermore, the coefficient of anisotropy in the area ranges between 0.029 and 5349.78. The south-western boreholes have values that fall between the standard range of 1.39-1.66, indicating that those areas have boreholes with high productivity.In conclusion, most parts of the study area have excellent protective capacities and high potentiality.