JOHANNESBURG (miningweekly.com) – There is no evidence of water supply concerns related to the current drought compromising mining operations in South Africa, the Department of Water and Sanitation (DWS) tells Mining Weekly.
However, project management and engineering consultancy Royal HaskoningDHV mining director Berte Simons said last month that the drought could become a bigger problem in areas where underground water reservoirs, mining operations and communities interacted, as this would “inevitably” lead to mines and their host communities competing for water.
The department does acknowledge, though, that mining might have an aggravating effect during the current drought on the quality of the water supplied in certain parts of the country, as historical mining activities governed under the previous National Water Act of 1956 have damaged certain water resources.
“Current mine water uses must be authorised in accordance with the National Water Act of 1998, as this authorisation aims to ensure water resource protection and equity in water access and use,” the DWS stresses.
However, the department notes that the mining industry “is a relatively small consumer”, as it uses only about 2.5% of the nation’s water resources, while other sectors, such as power generation, the manufacturing industry and agriculture, use 2%, 3% and 62.5% respectively.
The DWS further states that most mines have long recognised the need to use water prudently.
The DWS states that surface gold miner DRDGold has substantially reduced its reliance on clean water sources.
Its mining operations are located adjacent to Johannesburg on the central and eastern Witwatersrand of Gauteng, covering about 62 km from east to west and 25 km from north to south.
DRDGold has established infrastructure to use purified sewage effluent water in its processes, with additional projects using other grey water sources also being considered, the department highlights.
According to DRDGold, about 6 Mℓ of sewage is treated and delivered to the company’s closed water circuit at its new Rondebult water sewage plant.
DRDGold CEO Niël Pretorius says, to further reduce the company’s dependence on potable water resources, it is in ongoing discussions with local government to increase the use of treated sewage water.
Other gold miners in Gauteng – such as Sibanye Gold, which has mines in the Westonaria-Carletonville area, and Mintails, which operates in Krugersdorp – also rely on grey water sources.
“Sibanye Gold, which acquired the assets of the former Gold One and Rand Uranium mining operations in Randfontein, has assisted with the treatment of acid mine drainage, leading to an improvement in the water quality in the Tweelopiespruit downstream of the discharge point,” the DWS points out.
Natural resource and development solutions provider SRK Consulting South Africa partner and principal hydrologist Peter Shepherd says “a win-win situation” for mines and communities can be achieved when mines partner with local authorities’ waste-treatment plants. Mines can use the treated effluent water in their operations, allowing potable water to be used by communities.
He notes that the improved use of mine wastewater through reticulation systems is becoming standard for new mines, while older mines are slowly improving their reticulation in order to use recycled water.
Drought Warnings Ignored
SRK senior hydrologist Dr Hartley Bulcock argues that the current drought seems to have caught many people off guard, but that “it really should not have,” as there were early indications that this was bound to happen in the near future.
“Rainfall patterns are very cyclical and the data indicated that South Africa was entering a dry period.”
SRK hydrologist Lauren Bulcock remarks that a mining company is often very enthusiastic about ensuring responsible water use, but the implementation of these programmes is much more difficult, owing to financial and/ or capacity constraints.
Hence, she believes that it is important that mining consultancies work with mine managers to implement water management strategies to assist in improving operations.
Adapting to Climate Change
Lauren Bulcock adds that many mines manage their water based on average rainfall, which is part of the problem, as they need to plan according to the cyclical nature of rainfall.
“Just because there was plenty of rain in previous years does not necessarily mean that there will be good rains in the years ahead,” she states, noting, however, that what does become more difficult is correctly predicting rainfall patterns when climate change is factored into the equation.
She adds that mines can no longer calculate their water use yearly and must plan in accordance with two- to five-year periods, while implementing flexible plans to adapt accordingly to changes in rainfall patterns.
Hartley Bulcock adds that people’s perceptions regarding climate change are that a massive shift in weather patterns will occur. However, he asserts that it is not the long-term average that is changing, but rather a change in rainfall variability, with more frequent extremes between seasons.
He emphasises that this is particularly important to consider in terms of mines that are located in the drier parts of South Africa.
Hartley Bulcock says it is, therefore, “highly probable” that the country will have drought years followed by flood years, owing to a combination of the El Niño cycle and climate change.
This scenario differs significantly from 40 years ago, when rainfall variability was much smaller in range, he adds.
“Any variation in rainfall has an exacerbating effect on water runoff volumes. A 10% reduction in rainfall can result in a 20% to 30% reduction in water runoff volumes; hence, it is not a proportional reaction and far more complex to calculate. This is . . . often missing in mine planning,” Hartley Bulcock elaborates.
Subsequently, water resources planning will become extremely difficult because the dams, spillways, culverts and drains of a mine will either be too big or too small.
Mining-affected communities face similar challenges, such as dependence on local infrastructure to supply them with sufficient water resources. Hartley Bulcock notes that, going forward, mining houses and local communities will, therefore, have to place significant emphasis on all parties having sufficient water resources.
Lauren Bulcock adds that water has to be managed on an integrated basis. “We have a lot of technologies and tools that enable us to do this effectively. Thus, it is imperative that mines use the tools at their disposal to accurately monitor and manage their water use.”
She highlights that large volumes of water evaporate in tailings dams, which is one of the first aspects mines can consider when saving water. The dams are traditionally managed by engineers and other technical staff, who mostly deal with infrastructure and not necessarily the way water is managed on site, she explains.
“Hydrologists can play a crucial role in ensuring a mine’s water resources are managed effectively and optimally,” Lauren Bulcock contends.
A mine’s technical team develops water reports based on the water that is already at the mine. But from a hydrological point of view, it is far more complex, notes Hartley Bulcock.
“We analyse all aspects of the hydrological cycle, including rainfall, groundwater ingress, evaporation and seepage, as well as the reticulation of the water throughout the mining end-process. This ensures we have a holistic understanding of water availability and use patterns.”
Shepherd states that there is currently a greater tendency for mines to have buffer water storage systems, as opposed to the attempt to evacuate the water from site as quickly as possible when there was too much water previously.
“This is because most mines’ stormwater dams are operated at minimum capacity to allow for sufficient storage to capture extreme flood events.
“However, the problem with trying to empty out the dam as soon as possible is that, during low rainfall – as is the case at present – there are serious water shortage challenges. There is, however, always a silver lining, as times of drought inspire innovative solutions to survive the water crisis,” he concludes.