Spatial analysis of groundwater quality in Bulawayo, Zimbabwe: Geogenic and anthropogenic contributions

Abstract

Over-exploitation of groundwater owing to urbanisation and industrialisation compromises its quality, spatially and temporally. The objective of this study was to analyse the spatial groundwater quality due to geogenic and anthropogenic activities in Bulawayo, Zimbabwe. Eighty boreholes were mapped and sampled for selected water quality parameters. The groundwater quality parameters that were adopted in this study were the temperature, electric conductivity, dissolved oxygen, pH, bicarbonate alkalinity, chloride, sodium, calcium, magnesium, sulphates, chlorides, potassium, iron, nitrates, fluoride, phosphates, arsenic, aluminium, zinc, strontium, barium and manganese. Groundwater samples were evaluated for drinking water suitability as per the 2011 World Health Organization (WHO) guidelines. Prediction of groundwater quality parameters at unsampled points was achieved by using the Inverse Distance Weighted interpolation method using Geographic Information Systems (GIS) software. Population, land use and geological data were superimposed onto the groundwater quality to generate integrated maps. There were noticeable distinctions in groundwater quality within different geological areas, particularly for fluoride, arsenic, sodium, calcium, chloride and strontium, signifying natural groundwater contamination. High levels of nitrate were detected near agricultural areas and in medium to high-density residential areas suggesting possible contamination from nitrogenous fertilizers and leakages from wastewater infrastructure respectively. The application of GIS to spatially map water quality, can be used by hydrogeologists and local authorities in planning, monitoring and protecting groundwater resources.