They find that reducing water to the river system will mean a loss to the environmental and Aboriginal cultural values of the river, its estuary and the Ramsar-listed Gippsland Lakes.
“Continued water resource use under a future drier climate will lead to the decline in environmental values of the Latrobe system and a loss of biodiversity,” an ecological assessment says.
Even under a “median” climate scenario, by the early 2040s the additional water used for mine rehabilitation will exceed average water availability. Yet some of the mines will take decades to fill.
These findings raise serious questions about government-approved plans to divert enormous amounts of water from the river system towards mine rehabilitation in the Latrobe Valley.
When coal power stations close, power station operators have a legal responsibility to rehabilitate mine sites. Hazelwood closed in 2017, while Loy Yang and Yallourn are set to close in the coming decades.
Environment Victoria campaigns manager Nick Aberle said the government and operators should rule out using water from the river system.
“It’s staggering that the mine operators are still putting forward proposals to fill the pits with water,” Mr Aberle said. While mining companies didn’t have current climate predictions when they made their original plans, that information was now available, he said.
If river water cannot be used, mine rehabilitation will become considerably more expensive because operators would have to buy recycled or desalination water, or undertake earthworks deeper into the pits. This could cost hundreds of millions of dollars.
Frankie Mills, a dairy farmer and irrigator with a family farm at Kilmany, in Gippsland, said about three-quarters of his water allocation came from the Latrobe River system. “If they are going to take extra river flow away, it might mean I don’t have enough water,” Mr Mills said.
During the Hazelwood Mine Fire Inquiry the two options identified for all Latrobe Valley mine pits involved filling or partly filling the voids with water.
Filling the Hazlewood pit alone will require 638 gigalitres, and take between 15 to 20 years without interruption. In comparison, Sydney Harbour holds approximately 500 gigalitres of water.
A third document released to Environment Victoria under freedom of information laws shows the Environment Protection Authority issued Hazelwood owner Engie with a clean-up notice in October. This notice reveals a coal ash dam on the floor of Hazelwood mine pit has been known to be polluting groundwater since 2005.
A spokesman for Engie said its plan to fill the mine void had been informed by more than 100 independent technical studies and was universally understood as the best way to manage fire risk and long-term ground instability in brown coal mines.
The company’s proposed access to future water would not impact on other users and would take account of environmental concerns and drought conditions, he said.
“Engie Hazelwood remains very focused on commencing the mine void fill so that our continued investment in the rehabilitation program can proceed,” the spokesman said.
There are international examples of mines being rehabilitated into pit lakes, particularly the former industrial Lausitz region of Germany. This region has higher rainfall than Victoria and they have faced challenges, including the slow filling rate and environmental contamination.
The state government said the region’s environment and rights of existing users would be fully protected during any process for mine rehabilitation.
“Earlier this year we established the Mine Land Rehabilitation Authority to work with the local community and ensure experts are providing independent advice in how the projects are managed over the coming decades,” a spokesperson said.
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Miki Perkins is a senior journalist and Environment Reporter at The Age.