Assessment of groundwater quantity and quality using spatial technologies : a case of City of Johannesburg Metropolitan Municipality

Abstract: Water is one of the most important resources on earth as it is one of the essentials that supports all forms of known life. In a broad context, water covers 70% of the earth’s surface, but only 3% of it is fresh water and a mere 0.6% of the earth’s water is potable. The increasing global water crisis arising from various anthropogenic factors and activities, including expansive population dynamics and climate change, is putting extensive pressure on surface water resources. Due to the decline in water supply, the need, desirability and groundwater usage has since become indispensable globally. However, one of the most important issues around groundwater globally is the availability and reliability of information on groundwater quality and quantity. Likewise, lack of reliable hydrogeological information has been identified as one of the reasons why groundwater has not been developed to its full potential in South Africa. Spatial technologies including geographic information systems have been used globally to detect, predict and analyse groundwater dynamics. Thus, this study used these resources to assess groundwater quantity and quality (in summer and winter) as well as the influence of selected physical parameters (geology and slope) on the groundwater within the City of Johannesburg Metropolitan Municipality over a 15-year period (2000–2015). Datasets consisting of groundwater recordings from 56 water monitoring stations and 261 boreholes, the study area boundary, elevation and geological data were obtained from the Department of Environment, Forestry and Fisheries, Department of Water and Sanitation, the City of Johannesburg as well as the Council for Geoscience. Kriging interpolation was used to interpolate both groundwater quantity and quality across the study area. Overlay analysis were then used to assess the influence of slope and geology on the groundwater. The study found a general increase in groundwater quantity from winter to summer season and from the year 2000 to the year 2015. Although a single comprehensive groundwater quality trend could not be established using the selected incompatible parameters, the quality was generally higher in the summer season than the winter season and also higher in the year 2015 compared to the year 2000. Areas with dolomitic aquifers and flat to gentle slopes were shown to have higher groundwater quantity. Good groundwater quality was found to be associated with hard basement rocks such as the Halfway House Granite and also associated with flat to gentle slopes, whereas poorer groundwater quality was found to be associated with soft bedrocks (carbonates and dolomites) and steeper slopes. The findings indicate that the City of Johannesburg has sufficient and potable groundwater, especially during the summer season and within the southern regions.M.Sc. (Geography