The construction of additional dams has been contentious, not least because of their rising costs.

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A 10-metre increase in Wyangala’s dam wall, originally identified in 2019 as a $650 million project to improve the reliability of water for farmers in the Lachlan River, could now cost as much as $2.1 billion, documents reported by the Herald this year show. The federal government has pledged to contribute the funds.

NSW Labor’s water spokesman Clayton Barr there was good reason to be sceptical when these projects were less than half the current price.

“If they were obvious and easily done, we’d have built them before.”

Helen Dalton, a water spokesman for the Shooters Fishers and Farmers Party, said the big problem with the projects was “the complete lack of transparency”.

“They also provide dreadful value for taxpayers’ money,” Ms Dalton said, noting that lifting the Wyangala dam wall would only increase water availability by 21 billion litres.

Taking a midway price tag at $1.5 billion, that would amount to $70,000 per megalitre, “making it the most expensive water in history”, she said.

NSW Water Minister Melinda Pavey said the state’s communities faced the full force of drought and water restrictions.

“With the threat of climate change it’s likely we will be faced with longer and more severe dry periods, punctuated by large floods which is why we are delivering more water infrastructure,” she said.

The Herald sought comment from NSW Treasure Dominic Perrottet.

Officials from the MDBA said any new dams would not increase the amount of water available for any particular river value and would even reduce it if there was more evaporation from a larger storage.

MDBA’s chief executive Phillip Glyde said the authority was concerned about the effect on the environment.

“You’re basically changing the time in which you’re using [the water],” Mr Glyde said. “You’re moving where you’re holding the water [so that] it’s a headwater storage rather than a wetlands if there’s a big flood.”

Any new dam would also require the particular state to resubmit its water resource plan for that valley, and show how it would alter environmental water flows.

“We’ve got to have a look at that change in the plan, and we have to accredit it,” Mr Glyde said.

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Mr Pitt also announced that it had set aside $25 million, split evenly by Queensland and NSW, to improve metering in the northern Murray-Darling Basin.

“This is all about ensuring we can get transparency and trust in the information you get...to give confidence to all users,” he said, adding the money would include boosting satellite monitoring water extractions.

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