Assessment of Water Quality Index of Groundwater Resources in Iwo Local Government Area, Osun State, Southwestern Nigeria

This study assessed the groundwater quality of 30 selected wells and boreholes in Iwo Local Government Area, Osun State, Nigeria. Groundwater sources were randomly stratified and identified according to the 15 political wards using hand-held GPS equipment. The sources were sampled during the rainy season (October) and dry season (January) to determine water quality. The physico-chemical and microbiological parameters of the water samples such as temperature, turbidity, total suspended solids, pH, electrical conductivity, total dissolved solids, total alkalinity, total hardness, chloride, sulphate, nitrate, phosphate, magnesium, calcium, iron, zinc, lead, manganese, cadmium, chromium, and total coliform were determined using standard methods. The results showed that total hardness, calcium, cadmium, sulphate, and phosphate had mean values above the acceptable values for rainy and dry seasons; their mean values in mg/l for the rainy season were 252.933, 98.267, 0.018, 305.119, and 1.762, respectively, while their values for the dry season were 299.633, 115.831, 0.020, 285.695 and 1.705, respectively. The Water Quality Index (WQI) values showed that 30% of the selected groundwater sources were fit for consumption while 60% were poor and 10% were unfit for drinking during the rainy season. During the dry season, 50% of the groundwater sources were fit for consumption, 40% were poor, and 10% were unfit for consumption