OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

5.3.6 Implications for water quality and quantity management
The available evidence suggests that the extensive areas of coal mining in this sub-catchment have had, and
will continue to have, very high impacts on the sub-catchment’s water resources and particularly, the water
quality of all streams and rivers. The primary cause of these impacts is the extensive acid mine drainage where
water of low pH, with high concentrations of total dissolved salts and metals, enters local water courses and
results in a complete change in the water chemistry. The large volumes of acid mine drainage and the long
period of time over which these discharges and seepages have taken place has resulted in the impacts still
being discernable (as altered water chemistry characteristics) over two hundred kilometres downstream from
the Witbank and Highveld Coalfields
These effects are also accentuated by seepages from power station ash dumps, as well as effluent discarded
by different industries, including the Highveld Steel Plant and various foundry operations. The small, closed
copper mining operations in the lower reaches of this sub-catchment have no impacts on the basin’s water
resources.
One of the positive aspects of increased salinity values caused by acid mine drainage is that the increased salt
concentrations tend to diminish the presence of suspended sediments in local streams and rivers by autoflocculating
sediments.
Overall, the serious nature of the impacts caused by mining or attributable to mining in this sub-catchment has
been the subject of concerted research and management attention for several years. The latest development
has been the launching of the COALTECH 2020 programme that seeks to harness the collaborative efforts of all
role players in a concerted attempt to derive appropriate and cost-effective management strategies that will help
to resolve these problems.
5.4 The Middle Olifants sub-catchment
5.4.1 General description
5.4.1.1 Hydrology
This sub-catchment comprises the portion of the Olifants basin between Loskop Dam and the junction of the
Selati and Olifants rivers. It receives upstream inflows from the Wilge and Little Olifants-Riet sub-catchments,
as well as the Steelpoort and Blyde sub-catchments. Within this sub-catchment, the most important tributaries
are the perennial Elands, Moses, Selons, Bloed and Makhutswi rivers, whilst several smaller tributaries, both
perennial and seasonal or episodic, enter from the north-west and south-east.
One very large impoundment on the Olifants River, the Mogoma Matlala (Arabie) Dam, provides water supplies
to numerous small towns and settlements in the sub-catchment, as well as large volumes of water for irrigation
schemes along both banks of the Olifants River. Nine other medium-sized dams are also located in this subcatchment
and supply water for domestic use and for irrigation. Many of the mines and industries in this sub-
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