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‘Too good to lose’

Friday, 13th April, 2012

By Andrew Robertson

The Commonwealth's bid to secure water savings for the Murray-Darling Basin from the Menindee Lakes failed because it did not meet NSW Government requirements.

The State Government has explained the reasons behind its decision to withdraw from the 'memorandum of understanding' it struck with the Commonwealth in 2010.

The two governments entered into the MoU to investigate and implement "key water reform initiatives" in NSW which centered on Broken Hill's water supply and the Menindee Lakes.

According to the NSW Department of Primary Industries (DPI), the NSW Government identified "three specific requirements" that needed to be met in the investigations.

After 18 months of work, said the DPI, it became clear that the Commonwealth's preferred option - which included decommissioning two of the four lakes and storing Broken Hill's water supply in an underground aquifer - failed to meet all three requirements.

Indicative capital costs of the proposed Managed Aquifer Recharge scheme were found to be prohibitively expensive.

"Further, this did not include the significant costs of water treatment and the on-going costs of operations and maintenance that would have to be borne by residents of Broken Hill and Menindee," the DPI said.

Another requirement, that there be no reduction in the reliability of water availability to downstream users, including those in NSW, Victoria and SA, was also unable to be met.

"The investigations showed there would be significant impacts on water availability to downstream users in sequences of dry years," the DPI said.

This was because the Commonwealth's preferred option involved effectively decommissioning two of the four lakes - Menindee and Cawndilla.

Hydrologic modelling showed that under the Commonwealth's proposal the lakes were effectively dry, at less than 100 gigalitres capacity, for 18 per cent of the time, as opposed to two per cent of the time under current arrangements.

"This gets worse if you overlay extended dry sequences under a future climate change scenario," the DPI said in an information paper, titled "Menindee Lakes water savings opportunities".

Ensuring the environmental values of the lakes were maintained, another NSW requirement in the MoU, would also have been compromised, according to the DPI.

The Commonwealth's proposal involved the surcharge and extended inundation of the two upstream lakes, including the floodplain of the Darling River that connects the four smaller lakes, which would destroy the habitat for "the enormous biodiversity found at the Menindee lakes".

The DPI said the Darling River Water Savings Studies had found other potential infrastructure works and changes to operating rules that would generate more modest water savings while protecting the value of the lakes.

"The NSW Government will continue to work with the Commonwealth to progress these options but it not prepared to compromise the enormous water supply benefits provided to all states and the natural values of the Menindee lakes, to meet unspecified environmental objectives downstream."

The Darling River Action Group (DRAG) said too much attention had been paid to the Menindee Lakes and the Commonwealth should be looking upstream to find water savings.

The MDBA's draft plan has set a goal of finding 143 gigalitres of water from the Darling River and its tributaries for environmental flows.

"There should be buy-backs or infrastructure upgrades to get more water to the Darling," DRAG Secretary Barney Stevens said.

Mr Stevens said DRAG did support some structural changes to the lakes.

These included making the outlet to Lake Menindee larger and putting a regulator between lakes Menindee and Cawndilla.

DRAG would also support the dredging of channels to access residual pools in lakes Menindee and Pamamaroo, and modifying the channel between the Darling River and Tandou Creek.

"We have said we'd support certain engineering changes to the lakes," Mr Stevens said.

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