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

4.13.5 Water quality data
The available water quality data refer only to the water quality in two dolomitic springs located at the headwaters
of the sub-catchment. As such, the data provide little insight into the general water quality of the subcatchment.
Future studies should seek to obtain details of all effluents discharged to the sub-catchment, as well
as information on agricultural return flows. These data will help decision-makers to appreciate the implications
of deteriorating water quality for irrigation water users.
4.13.6 Implications for water quality and quantity management
Most of the mining operations in this sub-catchment are relatively small or are still under prospecting permits.
Minor contamination can be anticipated from the operating chrome mines in the form of possible toxic
hexavalent chrome. Minor acid mine drainage impacts can also be expected but, since this is a relatively dry
area, this is unlikely to be significant. Some increase in suspended solids can be anticipated in the rivers and
streams located close to mining and quarrying (dimension stone) operations.
4.14 The Crocodile-Elands-Pienaarsrivier sub-catchment
4.14.1 General description
4.14.1.1 Hydrology
This sub-catchment consists of the area drained by the Crocodile River and its two main tributaries, the Elands
and Pienaars Rivers, from the area immediately to the north of the City of Johannesburg, to its confluence with
the Limpopo River (Figure 4.2). Elands River drains the area to the northwest of Johannesburg, whilst the
Pienaars River drains the area from Pretoria northwards to the Waterberg Mountains near the town of
Warmbaths. All these rivers are perennial and their flows are supplemented by substantial discharges of
treated domestic and industrial effluent. Flows in these rivers are also enhanced by water imported from the
Vaal River system to the south of Johannesburg, which is used principally for domestic and industrial water
supplies prior to treatment and discharge.
There are sixteen relatively large water supply dams located in this sub-catchment, all of which supply water for
domestic and industrial use as well as for irrigation activities. In addition to the larger water supply dams, the
sub-catchment also contains a very large number (> 850) of smaller farm dams that are used to trap runoff in
seasonal channels and supply this water either for livestock watering or for small-scale irrigation schemes.
Extensive areas of the lower reaches of this sub-catchment are internally draining and provide little or no runoff
to flows in the Limpopo River.
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