Balancing water resources

Water management is a significant issue for mining companies — and this goes beyond finding enough water for operations and the disposal of wastewater.

Increasingly, the issue involves the impact a mine has on the water supplies of its neighbours. Mining companies are frequently faced with finding ways to not only reduce the negative effects on communities bordering mine sites but also make positive contributions to the people living in them.

With the growth in the global population, people are settling in more remote areas and mining projects are being developed in ever more populated regions. As a result, a mine’s impact on the lifestyles and livelihoods of these communities must be considered. In addition, environmental regulations are becoming stricter, requiring greater attention to the potential impacts on local water supplies. This is resulting in a different approach to water management — one that strives to balance competing needs for the best use of the resource.

The mining sector has responded with better effluent treatment technologies and more rigorous environmental protection programs that minimize the impacts from mining on water resources, along with measures to reduce the amount of water used in mining operations and systems that reuse that water.

One development in water conservation is the increasing use of paste tailings systems in surface disposal. And other mining projects are collecting rainwater and using it at the mine site to lessen the dependence on shared water resources.

However, there are still opportunities for improvement.

For a look at the next stage in water policy for mines, consider the example of a mine in southeast Asia. Predating the mining company’s involvement at this location, significant water-quality issues had been identified — there was naturally occurring arsenic in the soil, and historical mining had affected the local water supply. Partly as a result of these issues, there were few sources of clean water available to locals.

The mining company is looking at ways to mitigate the background arsenic levels and remediate some of the effects of historical mining on the property. A public awareness program was launched to inform people about the health risks associated with arsenic. This is expected to help lead to an improvement in the quality of local water.

The mine’s ability to store water in its reservoir allows it to help augment the water supply in downstream watercourses during drier months. Other improvements will come at the end of the mine life cycle, when the reservoir is made available to the local population.

Other ways to mitigate impacts from mining operations on local water users include providing the local community with a more effective water supply system and/or an alternative water source.

The best possible use of water requires a thorough understanding of water flows between the various components of a mine, along with the associated downstream effects. This involves the development of a comprehensive site-wide water balance model to simulate the changing conditions or scenarios over the life of the mine.

A risk-based analysis on the performance of the mine-site water management system — based on both deterministic and probabilistic simulations — provides a rational means to determine, in advance, water supply needs. Such a study will also determine effluent quantity and quality, as well as potential impacts on the local water resource — and corresponding mitigation strategies.

Having accurate historic hydrological and meteorological information is vital to producing reliable simulation models of mine-site water management systems. This generally entails having years of site-specific data, which may not be available in some parts of the world, requiring extrapolation from other sources, reducing the reliability of simulations. Therefore, it is important to start gathering meteorological and hydrological data as soon as possible within the project cycle to establish an accurate baseline that will be credible with regulators, financiers and other stakeholders.

The success of a mining project is increasingly dependent on the ability of the mining company to show that the project uses water responsibly and its impacts on people and the environment are minimized through careful planning. Rational decisions on water use can be made with the aid of an appropriate planning tool such as a site-wide water balance model.

And seeking ways to improve the water resource for the local population should be a key part of a mine’s strategy to conserve water.

— Mei Lin Shelp and Shiu N. Kam (skam@golder.com) are members of the mining group at Golder Associates. They can be reached at 1-905-567-4444.