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

Soils in the sub-catchment can be divided into four main groups:
• Moderate to deep sandy and clay-loam soils on flat, gently-sloping and undulating terrain overlying
dolomite, limestone and sandstones in the upper reaches of the catchment;
• Moderate to deep sandy to clay loam soils lining long stretches of the Blyde and Ohrigstad river valleys in
their middle reaches;
• Moderate to deep clay loam soils over much of the middle portions of the sub-catchment (located away from
the river channels), overlying the more porous unconsolidated sedimentary and hillwash material; and
• Moderately shallow to moderately deep, coarse-grained sandy loam to clay-rich, fine-grained soils derived
from granites and gneisses over most of the lower reaches of the sub-catchment.
Most of the clayey loam soils are very suitable for irrigated agriculture when sufficient water is provided.
Virtually all of the suitable soils are contained within the jurisdiction of formal irrigation boards or Government
Water Control Areas. Further away from the main river channels, most of the land use is given over to smallscale
irrigation from farm dams as well as the raising of small and large livestock (dairy and beef cattle, goats
and sheep). A wide variety of crops are produced, ranging from intensive vegetable production to tobacco,
maize, citrus and sub-tropical fruits, sorghum and sunflowers. Minor areas of plantation forestry (mostly Pines
and Eucalyptus) are also located in the wetter portions of the sub-catchment.
A few small towns and numerous smaller communities are present in the upper reaches of the sub-catchment,
whilst numerous scattered settlements and small towns characterize the lower portions of the sub-catchment.
The number and density of population declines with increasing distance from the upper reaches. Most of the
towns in the sub-catchment are service centres for the agricultural sector and have small fruit and vegetable
processing operations.
5.6.1.4 Surface water users
All the towns in the sub-catchment rely on water supplied from small water supply impoundments located
nearby. In contrast, most of the settlements have to rely on water supplied from boreholes or from run-of-river
abstraction points and, occasionally (in the lower reaches), from local boreholes. The areas of irrigation
agriculture consume most of the water used in the upper reaches of the sub-catchment. Immediately
downstream of the Blydepoort dam, the large Blyderivierspoort Irrigation Scheme is a major water user. Water
from the Blydepoort Dam is also released on demand to flow downstream to the Phalaborwa Barrage on the
Olifants River, where it is used to supplement the declining Olifants River flows that are available to water users
in the urban-industrial complex at the town of Phalaborwa. Recent estimates suggest that the water from the
Blydepoort Dam may account for some 30% of the total water used by Phalaborwa.
A formal Irrigation Board controls the Blyderivierspoort Irrigation Scheme. Recent improvements in the methods
of delivering water to the farmers are likely to achieve a 40% reduction in water use by this irrigation scheme.
However, this “water saving” is seen as an ideal opportunity to improve the reliability of water supplies to the
large number of settlements in the lower reaches of this sub-catchment who lack access to formal water supply
infrastructure.
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