Abstract
Exploratory modelling of the impact of gold mining on groundwater in a strategic water area of South Africa was undertaken. A systems dynamics (SD) model was developed to simulate the impact of gold mining on water quality, focusing on groundwater contamination risk, within the context of competing developmental priorities around water resource development and the socio-economic gains from gold mining. The model also identified interventions to minimise the impacts by the year 2040. The study area was the Blyde River Catchment (BRC), which is part of the Olifants Water Management Area in South Africa. This area is an important contributor, currently and in the future, to freshwater flows and groundwater in the Olifants River Catchment, which is one of South Africa’s most economically important catchments. The model development process included a causal loop diagram–based problem conceptualisation, followed by the drawing of stock-flow diagrams and the determining of model parameters based on a combination of background literature, data from environmental impact assessments, and from the national Department of Water and Sanitation. The model showed the potential environmental risks of gold mine wastewater production and interventions to minimise these risks. The most effective intervention identified to reduce the risk of groundwater contamination was the development and use of synthetic-lined tailings dams. The baseline simulation result of sulphate loading of 5430 t/year can be reduced by 3070 t/year to give a simulated sulphate load of 2270 t/year in 2040 using this intervention. In comparison, the simulated wastewater recycling intervention only reduced the sulphate load to 4630 t/year and the wastewater treatment interventions to 3420 t/year. This project contributes to the exploratory modelling of an understudied region of the Olifants River Catchment that is a crucial provider of freshwater flows to the Olifants, which is threatened by increasing gold mining in the upper BRC. The SD model highlighted the importance of protecting the dolomitic aquifers in the BRC for the long term sustainability of the catchment, which is particularly important if groundwater development occurs.
Highlights
Global water systems, which are responsible for sustaining the natural environment, development and rapid population growth, are under stress due to increased demand and pollution [1]
The simulation results of these interventions and scenarios are represented by time series graphs which aim to compare baseline conditions and the impact of mitigation intervention scenarios on groundwater contamination risk
Strategic water areas substantially contribute to the economy by sustaining water for people, industry, and most importantly, the natural environment
Summary
Global water systems, which are responsible for sustaining the natural environment, development and rapid population growth, are under stress due to increased demand and pollution [1]. The study area comprises the B60A–D quaternary (hydrological) catchments, as determined by the South African Department of Water and Sanitation( Figure 1C) [13]. The most recent study which looked at the feasibility of developing groundwater resources by utilising the Malmani subgroup dolomites indicated that the groundwater potential contribution could be 39.5 mcm/year [16]. This is 30.5 mcm/year less than what was initially estimated, leaving the reconciliation strategy with a significant shortfall. While groundwater development is feasible, it is not as significant a resource as was expected and will come at a great expense [13] This highlights the need to keep the available groundwater as free from pollution as possible
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