Assessment of ground water quality status for the Tarkwa mining Municipality in Ghana

Abstract

The present study assessed the water quality index (WQI) based on physicochemical analysis of twenty­six ground water sampling stations in the Tarkwa mining municipality in Ghana. In calculating the WQI, seven parameters were considered; pH, nitrate, sulphate, total dissolved solids, chemical oxygen demand, sulphates and turbidity. WQI values range from 100.36 (sampling station B10) to 4294 (sampling station B6). The mean WQI is 825.89 (i.e., 8 times more than the upper limit for potability). All of the groundwater samples exceeded 100, the upper limit for drinking water potability. The high value of WQI at these stations could be attributed to the higher values of total dissolved solids, and turbidity in the groundwater. Approximately 35% of the samples had WQI values which were up to 5 times or more than the threshold value of 100. Fifteen percent of groundwater samples had WQI values more than ten times the threshold for potability. Pearson correlation coefficients among selected water properties showed a number of strong associations. Turbidity correlated strongly with sulphates. Similarly, pH showed strong associations with EC, TDS and sulphates. Multivariate statistical (principal component and cluster) analysis suggest that the data is a three¬ component system that explains 72% of the total variance. The analysis reveals that the groundwater of this mining area needs some treatment before consumption, and it also needs to be mitigated against the risk of contamination