The CSIR Water Research Institute
undertook water quality monitoring and assessment of the Southwestern and the
Coastal Rivers Systems of Ghana from 2005 to 2008 for the Water Resources
Commission of Ghana (WRC) under WRIS II Project, a Danish Government Funded
Project. The Southwestern and the Coastal Rivers Systems cover approximately 30%
of the total drainage basins of Ghana. A total of 19 surface water stations
were selected for the monitoring programme. The Adapted Water Quality Index
(WQI) was to be used as a tool to classify the overall ambient water quality at
the 19 different stations. The index classified water quality into one of four
categories: good (Class I, >80), fairly good (Class II, 50 - 80), poor
(Class III, 25 - 50), and grossly polluted (Class IV, <25). This paper
presents the Water Quality Index approach to the assessment of water quality of
the waters in the different stations during the period of study. These ten
water quality parameters were used to determine the water quality index (WQI):
Dissolved Oxygen (DO % Saturation), Biochemical Oxygen Demand (BOD), Ammonium
Nitrogen (NH4-N), Faecal Coliform (FC), pH, Nitrate as Nitrogen (NO3-N),
Phosphate as Phosphorus (PO4-P), Total Suspended Solids (TSS), Conductivity
and Temperature. Evaluation of the waters with the WQI indicated that most
Ghanaian waters are currently in Class II, the fairly good water quality state,
but with variations in this range within the seasons and stations, and from one
water body to the other. Potroase in the Densu basin had the best water quality
during the study period while Nsawam had the poorest. Efforts should be made to
prevent further pollution of the waters to improve their quality.