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

In the south-west of the sub-catchment, felsites and gabbros of the Rooiwater Complex are found at the foot of
steep hill slopes. Similar outcrops, comprising rocks of the Banderlierkop Complex, outcrop in the northwestern
portion of the sub-catchment. Both of these rock types are relatively easily eroded and contribute
increased levels of sediments in the valley depressions and river channels. Granitic and gneissic rocks of the
crystalline Basement Complex underlie most of the central and eastern portions of the sub-catchment. These
rocks outcrop at various points across the Lowveld, forming prominent hills or koppies. The exposed weathered
granites are easily eroded, particular where the vegetation cover is sparse or denuded. Accelerated rates of
sediment production occur in this region, with large amounts of coarse and fine sediments accumulating in river
channels. The eastern portion of the sub-catchment is marked by the Lebombo Mountains, consisting of acidic
and intermediate rhyolites and lavas of the Karoo Sequence. Small areas of Quaternary deposits line the broad
shallow bed of the Great Letaba River along its lower reaches.
A large number of dolerite dykes and sills have intruded the Basement Complex granites and gneisses. These
rocks are less resistant to weathering than their granite and gneiss host rocks and give rise to negatively
weathered linear features in the landscape, often forming or delineating drainage lines that become filled with
coarse rock and gravel fragments.
5.8.1.3 Pedology, agriculture and land use
Soils in the Selati sub-catchment can be divided into four broad groups or regions:
• Large areas of moderately deep to deep, reddish clay-rich soils in the upper reaches, occasionally
becoming leached to form pale-coloured kaolinitic deposits;
• Areas of sandy colluvial soils at the foot of the escarpment, grading into red sandy-clay soils in the western
part of the sub-catchment;
• Shallow, brownish to greyish-brown sandy soils overlying coarsely weathered rock in the central and
eastern portion of the sub-catchment; and
• Transported alluvial deposits of coarse to fine-grained sands and silts located along drainage lines.
The upper reaches of the Great and Middle Letaba sub-catchment contain large areas of plantation forestry
(both Pines and Eucalyptus) and there are important natural forests on the steep escarpment slopes and upland
areas. The central portion of the sub-catchment supports extensive rain-fed and irrigated agriculture, consisting
primarily of citrus and sub-tropical fruits, as well as smaller areas of cotton, oil seeds and vegetables. The
central and lower reaches of the Great Letaba River provide an important source of water for game farms and
livestock (cattle and goats) rearing farms. In areas located away from the main river channel, rain-fed
subsistence agriculture of drought-tolerant crops is important, with livestock rearing of cattle, goats and
donkeys.
Land use in the entire eastern portion of the sub-catchment is wildlife conservation, with the Kruger National
Park occupying the largest area. Several smaller game reserves and game farms are also located close to the
western border of the Kruger National Park in some of the driest areas of the sub-catchment.
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