Development Of An Integrated Water Quality Index For Monitoring Water Quality Of Selected Estuaries In Ghana

Abstract

There is currently no country-specific water quality index (WQI) for monitoring estuarine water quality in Ghana. This study addresses this gap by developing an integrated WQI for monitoring the quality of estuarine water in Ghana, i.e., IWQIGh. This was achieved by reviewing literature on limitations and potential of adapted WQIs for water quality monitoring in Africa; field assessment of water quality of Ankobra, Volta, Whin and Kakum Estuaries using physicochemical parameters and benthic fauna; and developing the IWQIGh using multivariate statistical approaches. From results, the Weighted Arithmetic and Canadian Council of Ministers of the Environment WQIs were the most adapted with major limitations occurring in parameter selection and final index classification schemes. Statistical approaches in parameter selection and logical linguistic descriptions in classification schemes were suggested to ensure objectivity in WQI development process. Moreover, Kakum and Whin Estuaries were moderately polluted. Despite the moderate pollution levels, Kakum was the most diverse of the four estuaries. Based on ecological stability, Kakum Estuary was ecologically healthier than Whin, Volta, and Ankobra Estuaries, in that order. The most representative parameters for IWQIGh that contributed to high index values included nutrients, turbidity, electrical conductivity, chemical oxygen demand as well as pollution-tolerant low scoring taxa. Based on the IWQIGh, the selected estuaries were categorised as “polluted-Class 4”. Incorporation of benthic fauna in the WQI development process in further studies was recommended to address region-specific concerns in Africa rather than adapting existing WQIs.