Resilience and risk in mining water management

Addressing water supply and related water challenges is a key part of successful and sustainable mining operations. Integrated Water Management (IWM) models can be used to help address water risks and provide resilience for mining companies. Here, GHD’s Scott Anderson, Caroline Holmes and Tyler Tinker share insights on how IWM is helping to effectively manage water in the mining industry.

Since humans first began extracting minerals from the earth and processing them into usable material, they have had to manage water. In many cases, too much, too little or poor quality water can limit mine production capacity and, in severe cases, completely halt it. Therefore, it is no surprise that optimising the management of mine water is not only an exercise in risk management, but also presents a major opportunity to increase mine efficiency and profitability.

With the increased focus on sustainable use of water, combined with the resource uncertainties that climate change presents, it is now more critical than ever for mining operations to manage their water systems effectively and build in resilience to water shocks that are becoming more and more common.

Often water and contaminant balance models consider each component of a mining project in isolation such as tailings storage facility, and they generally only assess a static design scenario rather than changes over the mine’s life. Impacts on other components of the system are often ignored or based on assumptions that may not adequately reflect the system complexity. This is especially true under extreme events, where Mine Water Management Systems (MWMS) are pushed to their limits and can behave in unexpected ways.

Integrated Water Management models

To overcome this, an approach using IWM models can provide insights and optimised solutions that could not be inferred by simpler models, avoiding situations where simplistic ‘worst case’ design assumptions may lead to over design.

Best practice incorporates all components of a MWMS, as well as the interdependencies between them to provide probabilistic outputs of the magnitude of impacts. Inputs from hydrological, hydraulic, hydrogeological, chemical and tailings specialists are essential. The modelling incorporates all of these inputs and the probabilities surrounding them to provide improved predictions of a MWMS behaviour and then assigns a likelihood to a certain impact occurring.

A model comprises a spatially lumped representation of the components of a MWMS and their interactivity including water supply and conveyance infrastructure, hydrological and hydrogeological processes, ore processing, water treatment, waste disposal and tailings storage facilities.

Scenario risk analysis

IWM models can be used to assess different operational and expansion scenarios over a mine’s life, to determine the impacts to the water system and also identify areas where capacity is constrained and optimisation opportunities exist.

A model can provide answers to the following water-related questions:

What type of capacity constraint exists – water surplus/deficit or inadequate quality
Where does the capacity constraint exist – tanks, dams, pump or pipeline
When does the issue manifest – immediately or in several years
Likelihood that the issue will occur under climate change
Impact on mine performance measures – ore production, safety or environment
Magnitude of the impact and what will be the cost – financial, environmental and social

IWM models can be applied to any mining operation but yield greatest benefits for complex MWMS. GHD has successfully implemented this approach to mine resilience and risk identification in large lithium, gold and iron ore mining operations across Australia to identify solutions that are time, cost and impact optimised.

Case Study
Water Treatment Plant Reject Water Diversion Assessment

GHD is playing a key role in helping iron ore mines in Western Australia to quantify and then manage the risk associated with their water systems. The client wanted to understand the implications of diverting Wastewater Treatment Plant (WTP) reject water from its processing facility to its evaporation ponds. The scope of the project also included assessing the risks of water surpluses or shortages into the future and providing options for risk mitigation.

GHD developed a water balance model of the iron ore mine and associated infrastructure, including an ore processing facility, a water treatment plant, a gas fired power station, a dam, several evaporation ponds and the runoff and dewatering from several mining pits.

The modelling:

Identified the proposal to divert WTP reject water from the processing facility to evaporation ponds would significantly increase the risks of impacts to ore production volumes and environmental non-compliance. Further analysis found increasing pit pump-out rates would not significantly improve the risks associated with their water systems.
Demonstrated that increasing the capacity of a discharge pipeline could significantly reduce these risks at a relatively minor cost.
Informed the client that these risks were unlikely to manifest for approximately five years, which provided a timeline for planning and implementation for the required upgrades.

Water as a resource is one the most significant issues facing the mining industry moving forward. Special measures are needed to manage water and so the use of IWM models for mining operations is a proven effective way to provide improved visibility of water related risks and opportunities over a projects life. It not only provides solutions for improvements to mine production and profitability, but also helps mining organisations use water more sustainably and de-risks potential impacts to local communities and the environment. This is particularly critical given the government and community focus on water scarcity and sustainable use of water resources for the greater good.