Finding new ways to manage water responsibly
Last updated: 4 February 2022
It may not be the cutest creature. But what the blind cave eel lacks in beauty, it makes up for in scientific value.
“It’s one of the world’s rarest fish – it’s found only in the Pilbara Coast and Barrow Island,” says Shane, who leads the team of 90 water experts in our Iron Ore business in the Pilbara, Western Australia.
“We discovered the eels were living in the aquifer near our Robe Valley iron ore mine, and so we needed to make sure that any future water activities, like dewatering, wouldn’t have an adverse effect on their habitat.”
As we dig deeper to get the iron ore used to make the steel found in everything from bridges to buildings, we often need to mine below the water table. To safely access the ore, as we dig down we need to remove the groundwater that would otherwise enter the pit. This is known as dewatering.
“Our job is to understand whether our dewatering activity could lead to a change in the groundwater level in local aquifers, and whether that would cause any adverse impacts on the aquifer, and on the animals and ecosystems that depend on it – like the blind cave eel,” Shane said.
Managing the impacts associated with dewatering and other water supply activities in the Pilbara are a long-term challenge for our business. To help us address this challenge, we have set a specific water target for our Pilbara iron ore business to complete six managed aquifer recharge investigations by 2023.
“Managed aquifer recharge” (MAR) is a process where we return water to aquifers in a controlled way, such as through boreholes or an infiltration gallery. A key part of our investigations is to determine the appropriate triggers that initiate operation of our MAR schemes. For example, if monitoring shows groundwater levels have declined to a pre-determined threshold or that dewatering in our mines has the potential to adversely impact environmental or culturally sensitive features, we identify this early and take steps to return water to the aquifer.
Over the last decade or so, MAR has come on a long way and is emerging as an important method for managing water resources responsibly in the mining industry.
“MAR is a pioneering and developing practice and its application in the Pilbara will be fundamental to improving our long-term environmental performance,” Shane says.
A shared resource
Water is a vital resource in the Pilbara, and we need to take into account a wide variety of needs.
“Water is essential for our operations,” says Shane, “We need to get access to ore when it is below the water table, and we need to keep the water available to our operations, our processing infrastructure and our camps.
“Water is also hugely significant for many other stakeholders and ecosystems in the Pilbara. We are in a surface water-scarce area, and although we get episodic rain – like cyclones – less than 2% of our annual rainfall finds its way back to the aquifers.
“So if we were to allow for natural conditions to recharge the systems, it could take many hundreds of years.
“Water also holds great cultural value for Pilbara Traditional Owners, and it is important we listen and develop an understanding of both the technical aspects of water but also its spiritual significance. MAR has the potential to help with this, by returning water to the aquifer.”
To be successful, MAR requires a thorough understanding of the hydrogeology in the region and finding a way to “recharge” the water in a way that suits the local environment and that gives proper consideration to our long-term water balance.
“Through our first two investigations, we have already learned a lot about how to design and engineer MAR systems.
“It’s all about being prepared, so if in the future, there is any indication our operations could adversely affect groundwater levels, we’ll be able to counteract that by returning water back to the aquifers.
“Closure is a real driver for our MAR investigations too.
“What we are learning now could be used longer term when we are closing mines,” Shane says.
Protecting a national treasure
Our team has also been looking at how MAR can help us protect water beneath the Karijini National Park, in the Pilbara, Western Australia.
We have started mining new deposits at our West Angelas mine, which are located a few kilometres from the boundary with the National Park – to reach these deposits we need to mine below the water table. Our approvals to mine them are conditional on there being no drawdown of the water table beneath the park.
"Hydrogeological investigations indicate there is potential for drawdown to occur beneath the Karijini National Park," says Shane.
"So we are putting the engineering in place to be able to maintain groundwater levels at the National Park boundary if needed.
“We've recently installed eight reinjection bores just outside the Park boundary and are now in the process of commissioning them."
Banner attribution: Holotype of the Blind Cave Eel, Ophisternon candidum © Mark Allen / Australian Museum 2018. Sourced from http://fishesofaustralia.net.au/Home/species/3203. This file is licensed under the Creative Commons Attribution 3.0 Unported license. (Note: We have expanded the black space around the image to suit our website requirements)
Lower image attribution: Blind Cave Eel, WA Museum.