Abstract
Understanding the groundwater dynamics is very important for strategic management of the water resource as urbanization and population growth put South Africa’s current water supply under tremendous stress. The groundwater resources potential and quality characteristics of the greater Johannesburg area, was thoroughly assessed using hydrogeochemical and environmental isotope techniques. The results of the geochemical and stable isotope investigations help understand the groundwater setting. Mixing process of fresh and polluted water is taking place at shallow zones within the weathered crystalline rocks and dissolution cavities in dolomites, where the rocks are characterized by the lithological and structural complexities. Furthermore, it was confirmed that the solute composition of the water results from two basic contributions: the reaction of meteoric water with weathered zones in the near surface area and direct infiltration through dolomite dissolution cavities. The results further indicate that the dominant movement mechanism of ions is through a diffusive process, which could be due to the limited availability of fractures with depth and its possible sealing by calcite precipitation. Consequently, the provenance of groundwater circulation is limited to shallow depths, however, dissolution cavities, fractured and sheared zones allow deeper circulation of groundwater. Moreover, the natural water quality is found to be highly impacted by acid mine drainage which is derived from the gold mines in the Witwatersrand basin as it has been observed in previous studies.
Highlights
Most countries, located within the arid and semi arid regions like South Africa, are categorized as water stressed [1,2] and depend primarily on groundwater as water supply for various developmental activities
The natural water quality is found to be highly impacted by acid mine drainage which is derived from the gold mines in the Witwatersrand basin as it has been observed in previous studies
The extreme precarious geoenvironmental setting of the greater Johannesburg area highly impacted the groundwater resource where the influence of the lithology and pollution on the water composition is manifested through the variation in the groundwater quality
Summary
Most countries, located within the arid and semi arid regions like South Africa, are categorized as water stressed [1,2] and depend primarily on groundwater as water supply for various developmental activities. Groundwater plays strategic role in supplying water for large irrigation fields in the area which is extracted from deep wells located within the dolomitic aquifer in the Transvaal Supergroup [3,4,5]. Understanding the nature of groundwater circulation and hydrogeochemical characteristics of the aquifers is crucial for sustainable development of the country’s water resources. Previous knowledge on the groundwater circulation media, natural quality of water could give insight on the state of pollution, which are generated from urban, irrigation, mining and industrial activities
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