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

Mountains, flowing first to the north-east and then east-south-east to join the Olifants River inside the Kruger
National Park shortly before it enters Mozambique. The “perennial” of the Great and Middle Letaba rivers are
only perennial in their upper reaches, becoming progressively more seasonal and episodic as they flow
eastwards. The three episodic tributaries rise at different points in the drier eastern portion of this subcatchment
within the Kruger National Park.
From the mid-1960s, flows in the Great Letaba River have declined progressively sue to rapidly increasing
water abstraction in the upper reaches. For the last twenty-five years, flows in the lower reaches of this river
have been entirely seasonal with no surface flow recorded during the dry winter months. This has posed
several problems for the Kruger National Park, as the Great Letaba River is an important source of water for
game animals. Accordingly, several small reservoirs were constructed along the lower reaches of the Great
Letaba River inside the Kruger National Park to provide assured supplies of water during the dry winter months.
There are several water supply dams and reservoirs located in the headwater zones of all the tributaries of the
Great and Middle Letaba rivers. These reservoirs supply water for domestic consumption in the several towns,
as well as irrigation water for the extensive areas of irrigation agriculture at the foothills of the Drakensberg
Mountains and along both banks of the larger rivers. In the drier central and eastern portions of this subcatchment,
the many settlements, farmsteads and small towns rely on boreholes or run-of-river abstraction for
their water supplies. During the dry winter months, these communities depend entirely on borehole water
supplies.
The sub-catchment also contains several hundred small farm dams. These provide important sources of water
for small farming operations, livestock watering and domestic consumption.
5.8.1.2 Geology
In its upper reaches, this sub-catchment is underlain by rocks of the Transvaal Sequence, which form the major
portion of the Drakensberg Mountain range. Quartzites, silicified sandstones, chert, hornfels, basic lava and
dolomite dominate the lithology. The dolomite outcrops, in particular, are important sources of good quality
water in the upper catchment and contribute water throughout the year. These rocks form prominent landscape
units along the watershed.
Further to the east and north-east, rocks of the Gravelotte Group (part of the Murchison Sequence) and
Rooiwater Complex outcrop and are visible as a range of low hills that trend south-west to north-east.
Quartzite, schists, basic lava and granitic rocks, with considerable base metal mineralization and numerous
pegmatites on the periphery of this formation, dominate the lithology. In the south, these greenstone formations
are referred to as the “Murchison Greenstones” and contain important deposits of antimony and gold, with minor
deposits of mercury and zinc. In the north, these formations also outcrop as low ranges of folded hills and are
named the “Giyani Greenstones”. The Giyani Greenstone area has a very similar lithology to that of the
Murchison Group and is also heavily mineralised, with important gold deposits. An unfortunate aspect of the
lithology here is the presence of arsenopyrite.
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