Hydrochemistry and water quality index (WQI)application in the assessment of groundwater quality in Oyo State, Nigeria.

Abstract

Groundwater quality assessment and the application of WQI in Oyo State, Nigeria were studied. Twenty five of the 33 LGAs in the State were selected while five villages were randomly selected from each for this purpose. Samples were collected from each of the villages and analysed. The results revealed that the groundwater is generally fit for human consumption by World Health Organisation standard. Weighted average water quality index analysis showed that the groundwater in the 24 LGAs fell in the 'excellent water' while one fell in the 'good water' category indicating its potability. Multivariate analysis showed that four pairs of water quality variables (EC and TDS, EC and NO3, TDS and NO3, Na+ and K+) have positive correlations. Only EC and TDS correlate positively with WQI results and so positively influenced WQ analysis results. Regular investigation is recommended for the optimal relevance of WQI in water quality management.