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Mining companies hunting for resources to fuel Australia’s renewable energy transition have bold plans to build mineral sand mines, and minerals processing plants, in the heart of Australia's Murray-Darling Basin.
Farmers fear those plans, which involve pumping billions of litres of water each year into pits at proposed mine sites, will raise the surrounding water tables, increasing salinity on land farmers rely on for their livelihoods.
These concerns are particularly acute in the fertile wheatbelt south of Swan Hill, in northern Victoria, where lush paddocks of cereals and legumes sit atop a groundwater system that contains water as salty as the ocean.
The region was once an ancient inland sea, and mining company VHM has discovered it is rich in rare earth elements, zirconium and titanium.
Farmers in the region have treated the aquifer with caution since they began farming the land 150 years ago, knowing if the salt water rose too close to the soil's surface, trees and crops would die.
But they say a proposal to build a mineral sands mine in the heart of the region risks doing just that.
Near the town of Lalbert, VHM has proposed a 1,500-hectare mine — digging down to a depth of up to 43 metres to extract minerals that are increasingly valuable for building the components needed for modern technologies like wind turbines and electric vehicles.
The company is proposing to pump between 3.1 and 4.5 gigalitres of water per year from nearby Kangaroo Lake to extract and process the minerals before sending them away for sale.
Farmer Stewart McCann said he was concerned pumping that volume of water into the site would cause the surrounding water table to rise.
"There will be areas that are prime country that will be affected with an overloading of the water tables," he said.
"The water table is salty. It's saltier than sea water. It'll kill the crops and the trees."
Hydrologist Phillip Macumber, who was the first person to map the Parilla Sands aquifer below VHM's proposed mine site decades ago, said pumping large volumes of water into the area would cause "mounding", or a localised rise in groundwater.
"What bothers me ... is these pits are enormous," he told an inquiry into the proposed mine.
"That mine is going to be at least 7 kilometres long."
As the groundwater flowed from east to west through the site, Dr Macumber said the mine would "act as a barrier, similar to putting a dam wall in, which will raise the groundwater".
"It brings home the instability in the southern Australian groundwater systems. It doesn't take much to tilt them from that stable, low level system, to fill them up," he said.
An independent panel held an inquiry into the proposed mine earlier this year, and has submitted its recommendations to Victorian planning minister Sonya Kilkenny.
Ms Kilkenny is yet to make a decision on whether the proposed mine can go ahead.
A VHM spokesperson said in a statement the company was "not in a position to provide comment on matters which are subject to the minister's assessment".
If the company was granted a mining licence, "VHM will be required to implement a groundwater management plan as the framework to manage and mitigate potential risks to groundwater," the spokesperson said.
Lake Victoria 'at risk'
Across the border in south-west NSW, a second mining company has submitted a proposal to dig for mineral sands 25km from Lake Victoria — a natural lake used to store water for South Australia.
Mining company RZ Resources has submitted plans to use a dredge-mining technique to extract the valuable minerals, then process them at the site, known as the Copi project, before shipping them to Brisbane by rail.
The plan would require pumping between 4.5 and 9.6 gigalitres per year of highly saline groundwater up to the surface to use at the mine, according to the Environmental Impact Statement the company submitted to the NSW government.
Farmer Warren Duncan, who runs merino sheep on a pastoral lease between the proposed mine site and Lake Victoria, said the company's plans could kill vegetation on surrounding agricultural land.
"If you bring it [groundwater] up to the surface and put it on the actual topsoil, it'll kill it, and it'll kill it for years," Mr Duncan said.
"It's probably better than Roundup [herbicide] as far as it's very long term, as far as absolutely destroys the soil."
Mr Duncan said bore tests at a site close to the proposed mine found the groundwater in the area measured about four times saltier than seawater.
Retired mining engineer Ian Magee, who has been campaigning alongside farmers against both proposed mines, said he was concerned waste from the Copi project, including salt and heavy metals, could flow towards Lake Victoria during a storm event.
“When storm water moves through the site, the risk is that saline groundwater flows downstream, of course, and in this case, the catchment about 25km away is Lake Victoria," Mr Magee said.
Lake supplies drinking water to SA
Even though Lake Victoria is in New South Wales, it is operated by SA Water, the South Australian water authority.
When full, the wide, shallow lake holds 677 gigalitres of water and covers 12,200ha.
RZ Resources chief executive Campbell Jones said in a statement: "The Copi Project's Environmental Impact Statement includes a comprehensive assessment of groundwater impact, which has been made publicly available as part of the exhibition process."
Water authority SA Water responded to the EIS with the concern that "the proposed short and long-term monitoring of groundwater bores and network does not seem sufficient to provide advance notice of any issues that may be caused by the proposal".
The authority called on the company to install and publicly report "additional monitoring on the local and regional networks".
"This monitoring should be enduring as any impacts will potentially last into the decades to remediate," the authority wrote.
Mr Jones said RZ Resources had been "considering the responses received from individuals and government agencies" and would respond to them.
A spokesperson for the NSW Department of Planning, Housing and Infrastructure said in a statement the government would decide whether to approve the proposal based on the "adequacy" of RZ's response.
"DPHI will then undertake a comprehensive assessment of groundwater and surface water impacts, including on Lake Victoria. This will be guided by advice from experts from the Water Division of NSW Department of Climate Change, Energy, the Environment and Water," the spokesperson said.
Project by project approach 'failing'
University of Sydney postdoctoral research associate and Minerals Policy Institute chairperson Lian Sinclair said Australia needed to update its mining assessment process to consider the cumulative impact of multiple mining projects on a region as a critical minerals mining boom got underway.
"This is particularly pertinent in regions like in the Murray basin, where there are several different mineral sands proposals at the same time," Dr Sinclair said.
In addition to RZ Resources' proposed Copi Project and VHM's proposed Goschen mineral sands project, mining company Iluka has received approved to mine for mineral sands at Balranald in NSW.
Astron Corporation has also received approval to mine for mineral sands at Minyip in Victoria.
"The project by project approach is failing. We need a cumulative regional approach," Dr Sinclair said.
A spokesperson for the federal environment department said in a statement: "Landscape scale considerations are generally addressed by state and territory laws."
"As part of the government's Nature Positive reforms, national environmental standards will be implemented to ensure critical habitat and other significant environmental matters are protected, including from cumulative impacts," they said.
"The Nature Positive reforms also include the development of 'regional plans' as a tool available to manage the cumulative impacts of industries such as critical minerals mining at a regional scale.
None of the current regional plan pilots are located in the Murray Basin area.
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