A new monitoring system being used at a mine in Western Australia's Pilbara shows promise for future mining legacy management, helping companies to monitor evaporation rates in mine pit lakes.

The challenge

Managing discontinued, legacy mines

Managing discontinued mining sites for future natural resource production comes with numerous challenges, of which water management is a high priority.

A disused open-cut mine which has been excavated beneath the water table is likely to fill with water from rising groundwater and rainfall, forming a pit lake with a unique chemical composition.

Effective environmental management of such a site depends on information about the geology and any possible contaminants remaining in the mine tailings, as well as the lake's water balance—the ebbs and flows of water and its evaporation from the lake.

Our response

New technology allows greater access to evaporation data

We have been working to understand and measure the water balance in the pit lake of a major mining company's disused iron ore mining site in the Pilbara.

Researchers have deployed a new monitoring system that improves evaporation estimates through a combination of measurements and improved computer models.

The evaporation data collected is then coupled with information from surrounding weather stations to generate computer models to help predict how evaporation rates will change as pit lake levels rise in the future.

The system is designed to float upon the surface of open-cut mine lakes and take daily evaporation measurements, with its durability allowing it to remain within the mining site for long periods of time, and because it’s autonomous it requires minimal labour once deployed.

The results

Accurate modelling data for management practices

The evaporation monitoring system has been successfully deployed in the Pilbara, which experiences high temperatures and evaporation rates, demonstrating its ability to provide accurate evaporation data under extreme environmental conditions.

The combination of accurate data and evaporation modelling will enable the team managing the mine to predict pit lake levels and possible negative impacts from changing water levels on the surrounding environment. Anticipating the evolution and impact pit lakes pose for adjacent water resources is crucial for effectively managing the long-term legacy of mining.

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