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

• Any effluent discharged by a mining operation affects the quality of the receiving environment and the
fitness of the receiving water for other users. In arid areas, mining effluents lead to increased salinities and
their associated effects. Examples of this can be seen in the drier regions of all three of the river basins
evaluated in this report.
• Importantly, mining operations need reliable water supplies that will be provided with a very high level of
assurance. This is necessary to avoid the risk of any processing problems in the hydro-metallurgical
processes that may be caused by water shortages. Because of the unreliability and variability of rainfall in
many parts of southern Africa, dams and water supply reservoirs are needed to ensure that the mining
operations receives the water it needs. Construction of a dam on a river has far-reaching impacts on both
ground water and river flows, as well as water quality, downstream of the structure. Typical examples can
be seen at the Phalaborwa Barrage in the Olifants basin, downstream of the Vinetia Diamond Mine near the
Limpopo River, and downstream of the Selibe-Phikwe copper-nickel mine near the Macloutse River in
Botswana. Similar, related, effects occur when hydroelectric impoundments are built to supply electricity
needed for mining and for metal refineries. The Kariba Dam that supplies electrical power to the Zambian
Copperbelt is a good example of this type of effect.
6.1.7 Impacts caused by small-scale (artisan) mining
Small-scale mining activities, particularly the unlicensed (artisan) type, seldom have access to appropriate
technologies or mining methods. Most of the activities are not subject to proper health, safety and
environmental controls, nor are they easily manageable by mining authorities. Specific concerns relate to:
• Accelerated erosion of areas adjacent to workings that have been de-vegetated for construction materials or
fuel wood leads to increased suspended sediment loads in nearby streams and rivers. Examples of this can
be seen around the Ndola Rural emerald workings and the Lundazi aquamarine workings in Zambia
• Excavation of flood terraces and riverbanks increases the instability of these riverbanks and enhances the
likelihood of increased flood scouring. Examples of this have been recorded from alluvial gold diggings on
the Mazowe River in Zimbabwe and Mozambique.
• Excavation of river sediments exposes these sediments to oxidizing conditions and enhances the
solubilization and release of any metal ions that may previously have been previously trapped as insoluble
sulphides. Examples of this can be seen in the Mazowe River in Zimbabwe.
• Gold panning and operation of sluice boxes increases loads of suspended sediments in downstream
reaches. Examples of this have been recorded from the alluvial gold diggings on the Luenha River in
Mozambique, the Mazowe River in Zimbabwe and Ruhuhu River in Tanzania.
• Washoff of mercury used to concentrate gold leads to increased risks of mercury toxicity to aquatic and
terrestrial organisms, as well as to the miners. Examples of this have been recorded on the Mazowe alluvial
gold diggings in Zimbabwe.
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