Since 2005, the Water Resources Commission (WRC) has computed an annual Water Quality Index (WQI) using data from its national biannual monitoring programme to provide a simplified assessment of surface water quality across Ghana. The WQI is derived using a weighted aggregation of key water quality parameters.

WQI Score Classifications

· 81 to 100: Good to excellent (Class I)

· 51 to 80: Fair to good (Class II)

· 25 to 50: Poor (Class III)

· Less than 25: Grossly polluted (Class IV)

Data Gaps and Interpretation

· Stations like Ampansie (Ankobra River) still face severe access challenges, leading to missed sampling events and underreported WQI scores. These gaps are flagged and are not due to errors in WQI calculations.