Groundwater Quality Assessment in Ondo City, Southwestern Nigeria

Groundwater is an important source for drinking water supply in the hard rock terrain of Ondo town, southwestern Nigeria. Groundwater quality was investigated in Ondo town to determine its suitability for domestic use and human consumption. To achieve this aim, twenty-five groundwater samples were collected and analyzed for physiochemical parameters. Water quality was classified using the Water Quality Index (WQI). Except for phosphate, the results demonstrate that the groundwater characteristics were below the World Health Organization's allowed range. The dominance of main ions was Na ⁺> Ca2+ > K+ > Mg2+ \({Na}^{+}\) ${\mathit{Na}}^{+}$ > \({Ca}^{2+}\) ${\mathit{Ca}}^{2+}$ ˃ \({K}^{+}\) $K^{+}$ > \({Mg}^{2+}\) ${\mathit{Mg}}^{2+}$ for cations and \({{HCO}_{3}}^{-}{{>{Cl}^{-}>NO}_{3}}^{-}\) ${{\mathit{HCO}}_3}^{-}{{>{\mathit{Cl}}^{-}>NO}_3}^{-}$ ˃ \({{PO}_{4}}^{2-}\) ${{\mathit{PO}}_4}^{2-}$ ˃ \({{SO}_{4}}^{2-}\) ${{\mathit{SO}}_4}^{2-}$ for anions. Within the research region, the WQI varies from 52.69 to 118.07. With the exception of a few isolated regions in the study area, WQI shows that the bulk of the samples are of good quality, implying that the groundwater is safe for consumption and other household applications. Groundwater in places where the quality of the water is declining has to be treated before being used.