Integrating microbiological and physico-chemical parameters for enhanced spatial prediction of groundwater quality in Harare

Abstract

We predict groundwater quality to ascertain suitability for drinking purposes in the City of Harare, using a geostatistical approach. Forty-four (44) groundwater samples collected across different parts of the City of Harare were used. Samples were analysed for twelve physico-chemical and microbiological parameters (i.e., pH, conductivity, calcium, magnesium, hardness, sodium, iron, potassium, nitrates, sulphates, turbidity, and total coliforms). An aggregate Groundwater Quality Index (GWQI) was then calculated for each sample. Ordinary kriging based on a spherical model was applied to predict GWQI in unsampled areas, resulting in the generation of the first integrated groundwater quality map for the City of Harare. The results indicate that approximately 57% of the groundwater in the city of Harare is below the acceptable standard for human consumption based on World Health Organization guidelines. The approach described here can be replicated in other cities to generate groundwater quality thematic maps that incorporate microbiological properties of water to safeguard public health.