Hydrochemical characterization and vulnerability assessment of unconfined groundwater systems in Ore area, Southwestern Nigeria

Abstract

The inhabitants of Ore and its environs, Southwestern Nigeria, rely exclusively on groundwater for their domestic, industrial and irrigation purposes such that there is the need to identify and subject the recharge and discharge areas for pollution potential integrity assessment. A total of 144 dug wells were selected for the study. Topography, water table levels and hydrochemical trend methods were employed to identify twelve recharge and eighteen discharge areas. Wells in each of the areas were selected and subjected to hydrogeochemical tests to determine their hydrochemical facies types. Results showed that concentrations of cations and anions are in the order of Ca2+> Na+> Mg2+> K+ and HCO3− > Cl− > SO42− > NO3−, respectively. The dominant hydrochemical facies is Ca–HCO3 type. These results were integrated with DRASTIC parameters to determine their pollution potentials. The results showed that both the recharge and discharge areas have low pollution potential based on their DRASTIC index values. Water quality indices result of Ore groundwater fall within good to excellent/very good categories with 31.43% and 68.57%, respectively. This study indicated that groundwater sourced from both recharge and discharge areas is safe for domestic and agricultural purposes and that the groundwater is generally less vulnerable to pollution.