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

4.15.1 General description
4.15.1.1 Hydrology
This sub-catchment consists of the area drained by the Matlabas and Mokolo rivers and their main tributary
streams. These two small river systems flow northwards or north-westwards from the area to the east of the
town of Thabazimbi, joining the Limpopo River (Figure 4.2). The flow patterns in these two rivers is very
variable as a result of the prevailing low and unpredictable rainfalls (average 450 mm) and the rivers normally
only contain surface water during the summer months. Most of their tributary streams are episodic and only
flow for short periods of time after local rainfalls in their vicinity. The two rivers contain four small dams and
numerous smaller farm dams that are used to supply water for domestic and irrigation purposes, as well as
livestock watering (Boroto & Görgens, 1999).
4.15.1.2 Geology
The geological features of this sub-catchment are relatively simple. Porous consolidated and partially
consolidated sedimentary strata, predominantly sandstones, underlie the upper two-thirds of the sub-catchment.
This is succeeded by a broad band of intercalated arenaceous and argillaceous strata and undifferentiated
sedimentary extrusive and intrusive rocks, mainly granites and gneisses, together with coal-bearing rocks of the
Karoo Supergroup, in the lowest reaches alongside the Limpopo River (Midgley et al., 1994).
4.15.1.3 Pedology, agriculture and land use
Soils in the sub-catchment can be divided into three main groups:
• Moderate to deep sandy loam soils on the sloping and undulating terrain in the upper reaches of the subcatchment;
• Moderately deep sandy loam soils lining long stretches of the valley bottoms in the middle reaches of the
sub-catchment; and
• Shallow to moderately deep sandy soils in flat and undulating terrain in the lower reaches of the subcatchment.
Most of the clayey loam soils are highly suitable for commercial agriculture when sufficient water is provided.
Virtually all of the suitable soils along the Mokolo River 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 small-scale livestock farming as well as the raising of game animals. Virtually no irrigation takes
place along the Matlabas River due to the scarcity of water. In the Mokolo irrigation schemes, a very wide
variety of drought-tolerant crops are produced, ranging from Cotton, Citrus and Sub-tropical Fruits, to Sorghum,
Sunflowers and Soya bean.
A few small towns and several small settlements are present in the upper reaches of the sub-catchment, though
population densities decline with increasing distance downstream. The north-eastern portions of this subcclvii