ASSESSMENT OF HOW WATER QUALITY AND QUANTITY WILL BE AFFECTED BY MINING OF THE WATERBERG COAL RESERVES

摘要

From local and international experience, it is known that coal mining has a pronounced impact on surface and groundwater quality and quantity. The influx of water may be as low as 1% of rainfall for deep border and pillar mines with no subsidence, to as much as 20% for some opencast mines (Hodgson et al. 2007). Such differences have significant impacts on the quantity and quality of surface and groundwater resources on the local scale and further afield. The Waterberg coal reserves represent the only large area with proven coal reserves remaining in South Africa. These reserves are targeted for large-scale mining in the foreseeable future. The application of lessons from other mining areas is appropriate here. The fact that new extraction options such as in-situ coal gasification are considered in addition to more traditional mining options, brings additional uncertainties to the fore. Although several factors, in addition to the effect on water resources, should be considered when selecting a mining method, the long-term effect on water quality calls for a careful consideration of alternatives. It is desirable that both developers and regulators be aware of the long-term liabilities and costs associated with different mining methods.The Waterberg coal reserves are situated in a relatively dry area. In view of the low rainfall and limited surface water resources, the necessary level of safeguard measures to ensure the quantity and quality of existing water resources is unclear. Experience from other areas cannot necessarily be extrapolated directly. A scoping level study was performed to consolidate the existing information on the geohydrology and pre-mining water quantity and quality of water resources associated with the Waterberg coal reserves. New data regarding water quality and acid-base potential for the different geological areas (through field investigations) and geology and mining methods, were obtained.