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

5.10.6 Implications for water quality and quantity management
In the absence of any mining activities, there are no implications for water quality or water resources in this subcatchment.
5.11 The Lower Olifants (Mozambique) sub-catchment
5.11.1 General description
5.11.1.1 Hydrology
This sub-catchment consists of the lowest portion of the Olifants basin in Mozambique and contains the area
drained by the Olifants River as it emerges into Mozambique from South Africa, down to its confluence with the
lower reaches of the Limpopo River (Figure 4.2). A few small episodic tributary streams also enter the Olifants
River in this sub-catchment and the Olifants River is known in Mozambique as the ‘Rio des Olifantes’.
The large Massingir Dam is located in this sub-catchment and controls all flows in the lower reaches of the
Olifants River before it joins the Limpopo River. Water is released from Massingir Dam to supplement flows in
the lower Limpopo River and to provide irrigation water for the large Chokwe irrigation Scheme. Most of the
small settlements located in this sub-catchment rely either on the Massingir Dam or on shallow hand-dug wells
for their water supplies.
5.11.1.2 Geology
The acidic and intermediate rhyolites and lavas of the Karoo Sequence that form the Lebombo Mountains, mark
the western boundary and dominate the geological features of the lower Olifants sub-catchment. Elsewhere,
extensive Quaternary deposits of the Mazamba, Jofane and Cheringoma Formations, underlie the subcatchment.
In addition, there are a few outcrops of Grunja and Sena post-Karoo complex rocks that consist
predominantly of alkaline dolerites and shales. Recent alluvial deposits are present along wide flood terraces
on either side of the lower Olifants River.
5.11.1.3 Pedology, agriculture and land use
Soils in the lower Olifants sub-catchment can be divided into three broad groups:
• Areas of sandy colluvial soils at the foot of the Lebombo Mountains, grading into shallow, reddish- or
greyish-coloured sandy-loam soils in the western part of the sub-catchment;
• Deep, brownish to greyish-brown sandy soils overlying coarsely weathered sedimentary rocks 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 and
riverbanks.
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