The geology and hydrogeology of parts of Minna Sheet 164NE

Abstract

A study of the geology and hydrogeology of part of Minna was conducted with the aim of determining the geological conditions controlling groundwater flow and storage and safe abstraction methods. Many boreholes have failed in this area principally as a result of poor understanding of the groundwater conditions and relying solely on geophysical surveys using Electrical Resistivity. The area is basically underlain by the rocks of the Nigerian Basement Complex system comprising chiefly of granites, gneiss, migmatites and schist. Geologic mapping was conducted on a scale of 1:25000, surface fracture orientations were mapped to determine the principal joint directions. Hydrogeologic mapping was conducted on existing dug wells and boreholes using gridding method. This information was used to plot the water level map and depth to water map. Groundwater in the parts of Minna studied occurs mostly within weathered to fractures portions of the underling rock. The a weathering profile is shallow and mostly between 3 – 10 m. water level contour map revealed that area with greatest potential are located within the central and northwestern portions of the area. No appreciable change was noticed in the water level change map. Sites that could be exploited for groundwater development showed targets areas having the highest water level and the least depth to water levels. Groundwater potential was found to be higher in areas underlain by granites followed by gneiss with scist having the lowest potential for groundwater storage and transmission. The schist in the part of Minna studied was found to be belong to the Birnin-Gwari Schist belt. This research has buttressed the need for geological and hydrogeological studies in choosing sites for the development of groundwater resources.