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Home The River Basin People and the River Governance Resource Management
The Limpopo River Basin
 Introduction
Geography
Climate and Weather
Hydrology
Water Quality
 Principles of Water Quality
 Human Impacts to Water Quality
 Groundwater
 Agricultural Impacts
Industry and Mining
 Impact from Mines
 Waterberg Coalfield
 Salinity
 Hardness
 Microbiological
 Heavy Metals
 Persistent Organic Pollutants
 Water Temperature
 Radio-nuclides
 Case Study: Upper Olifants River
 Water Quality Fitness for Use
Ecology and Biodiversity
Sub-basin Summaries
 References

 



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Water Quality: Industry and Mining  

Mining and industry can potentially have significant impacts on water quality if effluent release and water use are not appropriately managed. The extent and nature of impact is specific to the type of mining and industry activities, but some common impacts include iincreased metal content, salinity and sediment load (DEAT 2009).

The mining and industrial activities in the Limpopo River basin are generally associated with:

  • Mining (primarily coal, but also a variety of precious and non-precious metals);
  • Power generation; and
  • Chemical industries.

The map below shows the distribution of mines across the Limpopo River basin by commodity type, from Ashton et al. 2001.  The distribution of mines is heavily concentrated in South Africa in the Crocodile, Marico and Olifants sub-basins, with another significant cluster in the Zimbabwean portion of the basin.  With the exception of a mine at the coast, there are no mines in Mozambique and very few in Botswana.

Distribution of mining activities in the Limpopo River basin.
Source: Ashton et al. 2001
( click to enlarge )

Mining

While general information is available on the impacts of industrial and mining-related activities on water quality in the Limpopo River basin, one key study, under taken by Ashton et al. (2001) - Impacts of Mining and Minerals Processing on the Biophysical Environment in Southern Africa - provides one of the most comprehensive assessments to date. This report illustrates the distribution of mining and related industries across the major river basins of southern Africa and outlines the known impacts of these activities on water quality and the environment.

One of the main conclusions drawn from the report is that it appears mines within areas of low rainfall have low or localised impacts on water quality/resources. Mines located in the wetter regions of the basin have far more extensive impacts due to chemical weathering processes predominating. The table below summarises the findings of the Ashton et al. (2001) report for the Limpopo River basin. The information is presented per sub-basin.

To access a table of impacts of mining and mineral processing activities on the water resources of the Limpopo River basin, click here.

Acid Mine Drainage (AMD) is a significant issue in the Limpopo River basin.

What is Acid Mine Drainage?

  • Mine drainage is metal-rich water formed from a chemical reaction between water and rocks containing sulphur-bearing minerals.

  • The runoff formed is usually acidic and frequently comes from areas where ore or coal mining activities have exposed rocks containing pyrite, a sulphur-bearing mineral.

  • Metal-rich drainage can also occur in mineralised areas that have not been mined.

Source: US EPA n.d.

Acid Mine Drainage (AMD) is caused when the following conditions occur:

  • Disused mine shafts fill with water, entering from above (rainfall flowing in), or groundwater draining into the shaft and workings below the surface.  The water filling the mine shafts is polluted with metals and chemicals that were the bi-products of the mining activity and are then released into the environment, when the shafts overflow or into the groundwater, contaminating aquifers (IPS 2010); or,
  • Surface water or rainwater drains through surface mine dumps containing contaminated materials, chemicals and sediments, with similar results to those described above.

AMD is contaminated with salts (sulphates) and heavy metals, and is commonly of a low pH (acidic) (Mail and Guardian 2010).  Water contaminated with AMD is not fit for human or animal consumption or for irrigation.  Depending on the type of mining occurring in a particular mine, AMD can include radioactive isotopes.  The metals and chemicals typically found in AMD can cause serious illnesses in humans and animals, including organ failure, cancer and congenital birth defects (Mail and Guardian 2010).

As the Limpopo River basin includes numerous mines, active and abandoned, the environment is under significant threat from AMD.  As numerous mines in the region become abandoned or groundwater pumping programmes stop at abandoned mines, the threat from AMD increases.  According to a study performed by the CSIR in South Africa, the mining area around Gauteng has the potential to create 350 Ml/day of AMD - a number equated to the volume of approximately 140 Olympic swimming pools.

In addition to the direct impacts on humans and livestock, commercial interests selling fresh produce (fruit and vegetables) to the local and international markets have also expressed concern about the safety of future food production (Mail and Guardian 2010).

Industry

Power generation and the chemical industries have some of the greatest impacts of any industries in the Limpopo River basin. Industries are often associated with heavy metal deposition and an example of where this is an impending concern is in the river system surrounding the proposed Waterberg Coal Power generation project, located in the Olifants sub-basin. The river system in this part of the Limpopo River basin is generally considered of good quality and there are concerns that deposition from the coal power station during operation, and all of the associated impacts from building and day-to-day operations will greatly alter this ecosystem (SMS SIEMAG 2009). 

Effluent from a Copper-Nickel mine in Botswana, seeps into a watercourse.
Source: Vogel 2005
( click to enlarge )

The Document Library of the Limpopo RAK contains a report by Schippers and Schwartz (2005) that provides a valuable insight into the AMD situation at the BCL mine in Selibi-Phikwe, Botswana.

 



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