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

The mountainous area located to the northeast of the sub-catchment (close to the confluence of the Steelpoort
and Olifants rivers) consists predominantly of erosion-resistant quartzites shales and silicified shales of the
Transvaal Sequence. These rocks form steep-sided hills and cliffs with little surface soil.
The Steelpoort Valley itself is a steep-sided valley that trends in a predominantly northeasterly direction as a
result of the Steelpoort Fault. This regional structure appears to have been exploited by the Steelpoort River
during its evolution. The valley floor is covered with extensive, deep deposits of colluvium (hillwash), with more
recent (Quaternary) alluvial deposits located on the flood terraces on either side of the Steelpoort River.
5.5.1.3 Pedology, agriculture and land use
Soils in the sub-catchment can be divided into three main groups:
• Moderate to deep, stony sandy-clay loam soils on the foot slopes, as well as the sloping and undulating
terrain in the upper reaches of the sub-catchment;
• Shallow to moderately deep clayey loam soils lining the valley bottoms in the middle reaches of the subcatchment;
and
• Shallow to moderately deep fine to coarse sandy alluvial soils lining flood terraces on either side of the river
channels, particularly in the central and lower reaches of the sub-catchment.
Most of the clayey loam soils in the upper and central parts of the sub-catchment are very suitable for cultivation
and extensive rain-fed and irrigation agriculture is practiced in these regions. Water is pumped either directly
from the Steelpoort River or from small storage dams on tributary streams for small-scale irrigation. Minor use
is made of borehole water for irrigation, especially in the central and lower reaches, due to problems with
vanadium contamination and possible toxicity. Further away from the main channel of the Steelpoort River, land
use consists almost entirely of small- and medium-scale livestock (dairy and beef cattle) farming.
A few towns and several small settlements are located in the upper and middle reaches of the sub-catchment,
though population densities become much lower in the lower reaches of the sub-catchment. The central and
western portions of this sub-catchment support several small-scale subsistence farmers.
5.5.1.4 Surface water users
All the relatively small towns in the Steelpoort sub-catchment rely on water supplied from the water supply
impoundments. In contrast, most of the numerous settlements in the sub-catchment have to rely on water
supplied from boreholes, springs, and hand-dug wells or from run-of-river abstraction points. The areas of
irrigation agriculture consume moderate quantities of water in the upper and central reaches of the subcatchment.
Formal irrigation boards control the allocation of water to each of the irrigation schemes in the subcatchment.
Most of the mines and industries in the sub-catchment rely on water supplies from local boreholes.
5.5.1.5 Water management systems
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