Groundwater facie analysis in the upper Cross River basin, southeast Nigeria

Abstract

The study area lies between latitudes 6°02′N and 6°24′N, and longitudes 8°00′E and 8°16′E. The area is underlain by Abakaliki shale which belongs to Asu River Group of Albian age. The study determines different water types (facies) via analysis of major ion concentration of water samples using spectrophotometer of HACH DR/2010 series. Twenty (20) water samples were collected and analyzed. The laboratory results were further induced to statistical evaluations using Aqua Chem, and it showed that the groundwater of the area is hard and fresh. The results can be classified into five hydrochemical facies, namely Ca–Mg–Cl–S0₄, Ca–Mg–HCO₃–Cl–SO₄, Ca–Mg–HCO₃, Na–K–HCO₃ and Na–K–Cl–SO₄, all of which are dominantly alkaline water. Static water level was measured from hand-dug wells to determine hydraulic heads which delineated local potentiometric surface. Flow directions were deduced, and it showed isolated system of groundwater movement. Such localized pattern of water occurrence can be attributed to the underlying shaley aquiclude across the area. The hydraulic head info was correlated with facie analysis to interpret groundwater recharge zones.