Lithologic characteristics of parts of the crystalline basement complex of northern Nigeria in relation to groundwater exploitation

The extent of relationship between lithologic characteristics and productivity of crystalline aquifers has been considered with respect to rural water supply in the Galma river basin in northern Nigeria. Five lithologic units delineated across the basin were lateritic top soil, silty clay, kaolinitic sandy clayey silt, the weathered granite and the lowermost fresh basement rock. The crystalline Basement rocks were found to have areas of weathered and deeply fractured regolith which constitute useful aquifers. The overburden thicknesses were observed to be larger at the central and western parts of the basin than at the south eastern tip. Statistical evaluation showed that the regression line of yield on weathered zone thickness has a regression coefficient of +0.232, while the Pearson Product Moment Correlation analysis gave a correlation coefficient of 0.233. This revealed a weak, linear and direct interrelationship between the yield and weathered zone thickness, which suggests that the thickness of the weathered zone has a low but positive level of influence on well yield, but yield is not entirely dependent on weathered zone thickness.