Murray River research finds centuries-old ‘sand slug’ in Barmah Choke | Ralph-Lauren

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The Murray Darling Basin Authority (MDBA) says a “sand slug” accumulating in the Murray River is the result of historic mining practices rather than poor water management.

A report commissioned by the MDBA estimates more than three million tonnes of sand has settled in the Barmah Choke, the river’s narrowest stretch, which is located in southern NSW, reducing its capacity by 20 per cent over the past 40 years.

Nearby landholders have long claimed the choke’s capacity issues are due to bank erosion caused by the river running high.

It was a point of contention during the recent drought that Murray River irrigators frequently had a zero general security water allocation.

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The Barmah Choke restricts the flow of water down the Murray(Trudi Arter and Clint Jasper)

MDBA river management executive director Andrew Reynolds said it was thought the sediment came from mines that processed it through river channels to filter gold.

“We know it’s not sourced locally,” he said.

“It’s very different to the material in the banks in the river, so it’s not eroding from the banks into the bed, it’s coming from somewhere.

“That makes the river that little bit shallower, reduces the amount of water we can see downstream and it’s why we’re seeing a reduction in the capacity of the river.”

A sepia photo showing a wall of rock that has been subjected to a mining technique.
An example of sluicing on the Mitta Mitta, which the MDBA says may be the cause of silting at the choke.(Supplied: MDBA/State Library of Victoria)

‘Clutching at straws’

But John Lolicato, chairman of the Wakool River Association, is not convinced.

“The MDBA is clutching at straws and doesn’t want to acknowledge that there’s a natural constraint stopping large volumes of water from flowing down the river,” he said.

“This whole exercise seems to revolve around trying to find some way to justify putting in something that will allow water to bypass the choke.”

He said the answer was to restrict development downstream of the choke, which would require irrigation.

“Developers and others can’t continue demanding more water downstream, it’s collapsing the system and collapsing societies,” he said.

A narrow river banked with gum trees.
The Murray River narrows at the Barmah Choke.(ABC News: Peter Healy)

Mr Reynolds predicted that the findings would feed into a government investigation looking at how to improve management of the choke, a key part of the Murray-Darling Basin Plan.

He warned there was not an easy solution.

“It’s not as simple as just saying, ‘We’ll dredge the sand out of the river bed,'” he said.

“We’re not looking to increase the amount of water we can get downstream beyond what we’ve had to do in the past — we expect the existing trade limitations will stay in place.

“But what we need to be able to do is make sure we can service all that water demand downstream that’s already there, in a sustainable way, to take pressure off the choke.”

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