A Comparison of Water Quality Indexes for an Inland River

Abstract

The present study assessed water quality parameters and attempts to compare four different Water Quality Indexes (WQIs) for consistency, similarity and reliability in assessing the water quality of river Benue -an inland river- under wet and dry seasons. The results demonstrate that River Benue is continually being polluted in both dry and wet seasons by different sources, particularly domestic sewage and storm runoffs from farmlands. The quality of the water generally exceeded physiochemical and microbiological infection risk limits recommended in water quality guidelines concerning their use for domestic, recreational and irrigational purposes. Proper sewage treatment and river quality monitoring are needed to guard against hazards to public health and vulnerable river water resources. The WQIs applied were: CCME WQI, BC WQI, Dinius’ WQI and Weighted Arithmetic WQI. To evaluate the differences between these indexes, data on ten water quality parameters (Temperature, pH, total dissolved solids, electrical conductivity, Nitrates, Phosphates, biochemical oxygen demand, dissolved oxygen and faecal coliform count) for two distinct seasons from 6 river monitoring sites along the river Benue at Makurdi reach, were used. Significant discrepancies were observed in classification results between the Dinius’ WQI and the other three WQIs. Similarly, the WA and BC WQIs showed an over-optimistic rating due to their eclipsing limitation. Among others, it was concluded that any of the four indexes except Dinius’ index can be adopted but the CCME water quality index would be best suited for assessing water quality in River Benue.