Quality assessment of groundwater in Share and its environs, Southwestern Nigeria

Abstract

Groundwater quality assessment is of great concern for mankind due to its direct influence on human life. Increase in population of Share and its environs due to ongoing oil exploration in the Bida Basin and agricultural activities putting pressure on the groundwater resources. This study assessed the impact of human activities and urban growth on the quality of groundwater in Share and its environs, Southwestern Nigeria. Forty (40) groundwater samples were randomly taken in the study area from hand-dug wells and boreholes. Physico-chemical characteristics of the groundwater were examined. Results shows that the pH of groundwater ranges between 6.5 to 6.9 with a mean value of 6.7. The pH is acidic and falls within the world health organization (WHO) acceptable standards for domestic use. The groundwater's electrical conductivity ranges from 103 to 235 μS/cm, with a mean of 173 μS/cm. The electrical conductivity (EC) complies with WHO guidelines. Total dissolved solids (TDS) values falls between 118 and 265 with a mean of 185, which below acceptable limit of 1500 mg/l. The average mean concentrations of major ions in mg/l are (Ca²⁺ = 4.9; Mg²⁺ = 5.7; Na⁺= 0.8; K⁺ = 1.5; SO₄²⁻ = 77.0; NO₃⁻ = 36.1; Cl⁻ = 21.3; and HCO₃^- = 4.1) and all are found to be within WHO standard limits. The variations of chemical parameters are in order of abundance (Mg²⁺ > Ca²⁺ > K⁺ > Na⁺) and (SO₄²⁻ > NO₃⁻ > Cl⁻ > HCO₃^-) for cations and anions, respectively. The Piper’s diagram characterized the hydrochemical facies of groundwater as Mg(Ca)SO₄^2- - water type_.  Gibbs and Schoeller diagrams confirmed that the dominant process influencing groundwater chemistry in the study area is the interaction between water and host rock. The Wilcox diagram and Kelly's ratio indicated that groundwater in the study area is appropriate for irrigation use with values less than 1. In conclusion, findings from this study shows that the groundwater quality of the study area has not been adversely affected by the current human activities and population growth.