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Government modelling ‘no fix for lakes’

Thursday, 26th March, 2015

By Andrew Robertson

Computer modelling used to justify a proposal to lower the Menindee lakes’ drought reserve should be independently verified, according to a Broken Hill water consultative committee member, who says it would do nothing to stop the lakes being drained again. 

It would also result in less water for towns on the Darling River below Menindee, said Stan Dineen.

The State Government has said it is considering changing the current 640/480 rule that dictates when control of the lakes reverts from NSW to the Murray-Darling Basin Authority (MDBA) and vice versa.

Now management of the lakes is controlled by NSW once combined lake volumes drop to 480 gigalitres, and reverts back to the MDBA when levels reach 680GL. 

Under the proposed changes, control would go to NSW at 275GL and back to the MDBA once Lakes Wetherell and Pamamaroo are filled and water begins to be stored in Lake Menindee, or at around 615GL.  

The plan is part of proposed changes to the management of the lakes that would see the bottom lakes drained more quickly and more often, and remaining water kept in the upper lakes.  

NSW deputy director general of water, Gavin Hanlon, responding to concerns about the proposed changes, said computer modelling indicated adjusting the control rules “will not reduce allocation reliability” to Lower Darling water users.  

“The underlying premise of the suite of proposals is to draw down the lakes as far as possible, as quickly as possible, in order to reduce evaporation losses,” Mr Hanlon said in a letter to water consultative committee member Stan Dineen.

However, he said, any change in management of the lakes needed to be weighed against impacts on water users and the environment. 

Mr Dineen said yesterday he remained sceptical of the government’s modelling and was concerned that lowering the drought reserve to 275GL would not leave enough water for landholders and townships below Menindee during drought.  

“The 275 (gigalitres) might see Broken Hill through but we still have to look after the river,” he said.

“I intend to move at the next (consultative) meeting that Council get an independent consultant to verify that the figures are correct.”

Mr Dineen also said he was not convinced the changes would prevent a repeat of the situation at the beginning of 2013, when the lakes were drained in order to supply water to Murray River sites in SA. 

While NSW water minister Kevin Humphries reportedly told the consultative committee that the drought reserve will not be reduced, he declined the repeat the assurance this week.

Instead, he said he and Federal Environment Minister Greg Hunt had agreed that there should be 18 to 24 months’ of recoverable water in the Menindee Lakes System for Broken Hill.

“As the Darling River and the Menindee Lakes are an unreliable long-term source for the city’s water supply, the NSW Government is committed to looking at every available option to deliver water security for the region,” he said.

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