Groundwater Physicochemical Characteristics and Water Quality Index Determination from Selected Water Wells in Akure, Ondo State, Nigeria

The natural quality of groundwater is controlled by aquifer hydrology, geochemistry, and the geology. The principal objective of the study was to estimate and characterize the water quality parameters of groundwater using World Health Organisation (WHO) for drinking purpose. In view of objectives of the study, groundwater quality assessment was carried out in selected 67 water wells in Akure, Ondo State, Nigeria. The analyzed parameters are electrical conductivity, pH, oxidation potential (Eh), acidity, total alkalinity, total hardness, temperature, total dissolved solids (TDS), turbidity, calcium (Ca2+), magnesium (Mg2+), Sodium (Na+), potassium (K+), chloride (Cl-), bi-carbonate (HCO3-), sulphate (SO42-), and nitrate (NO3-). The temperature of the groundwater varies from 25.9 – 30.8°C with a mean of 27.9°C. All the water samples are colourless, odourless, and tasteless, with clear appearance. The recorded pH varies from 5.2 – 7.0 and characterized by an acidic condition. The EC of water samples is in the range of 53 - 874 S/cm (avg. of 189.8S/cm). The water type is a recharged water, with value of TDS ranging from 40mg/l to 424 mg/l, and an average of 96.7 mg/l, indicative of fresh water. The cations and anions satisfy the WHO standard for drinking purpose with about 95% compliance. The sequence of the abundance of the major ions is in the following order: HCO3-> Cl-> SO42-> NO3- for anions, and Ca2+> K+> Na+> Mg2+ for cations .The calculated values of WQI vary from 22% to 60%. The study area is widely (90% areal coverage) characterized by “Good water” in the range of 26 – 50%, with hardness varying from soft to very hard water. The “Excellent water” is only associated with Sample S-34 in the northwestern part of the study area, while “Bad water” fall (S-21, S-28, S-57, and S-65) within a small portion of biotite granite and migmatite geologic units.