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

local geological formations. High concentrations of the same trace metals in other river reaches are attributed
to the consequences of mining activities.
In some areas, complaints have been voiced about the prevalence of asbestos fibres in water used for domestic
consumption and laundry purposes. This is probably due to rain-induced erosion of waste rock dumps at the
closed Penge Asbestos Mine.
5.5 The Steelpoort sub-catchment
5.5.1 General description
5.5.1.1 Hydrology
This sub-catchment consists of the area drained by the Steelpoort River and its main tributaries, the Klip,
Dwars, Waterval and Spekboom rivers (Figure 4.2). All of these tributary rivers are perennial and rise on the
western slopes of the north-south trending Drakensberg Mountains and flow north-north-eastwards where they
join. The Steelpoort River then flows north-eastwards through a gorge in the escarpment before joining the
middle reaches of the Olifants River. Ground water inflows from the Chuniespoort dolomites provide an
important component of the water in the Steelpoort River.
Two small impoundments on the Dwars River provide water supplies to numerous small towns and settlements
in the sub-catchment. Most of the mines and industries, as well as several settlements, rely either on ground
water supplies via boreholes or direct run-of-river abstraction from the perennial rivers and streams in the subcatchment.
Several small farm dams in the upper reaches of the Steelpoort River and its tributaries trap water
for domestic purposes and for limited areas of commercial irrigation along the Steelpoort valley, as well as
livestock watering.
Flow patterns in the upper reaches of the Steelpoort River and its tributaries are relatively stable as these rivers
drain an area that receives some of the highest rainfalls recorded in South Africa (average rainfalls in the
headwater regions of these two rivers exceeds 1,100 mm per year). Whilst all the rivers are perennial, flows
increase during the summer months when rain is received. Smaller tributary streams in the upper reaches are
also perennial, though their flows are more variable.
5.5.1.2 Geology
The underlying geological formations beneath the Steelpoort sub-catchment consist predominantly of basic
rocks of the Bushveld Igneous Complex, consisting predominantly of magnetite-rich gabbros, norites,
anorthosites, pyroxenites and gabbroic rocks of the Rustenburg Layered Suite (RLS). These rocks form the
base of the relatively flat-bottomed valley areas as well as forming the watershed marked by the steep-sided,
more mountainous or hilly terrain to the east and west of the Steelpoort River.
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