AN $84-million proposal to stop the regular flow down Yanco Creek, the "jewel" of the Riverine Plains, won't save water for the environment as intended and could be redirected to big irrigators downstream, a new report says.
The plan, put forward by the NSW government, aims to return 20 to 35 gigalitres to the environment to help reach the Murray Darling Basin Plan's 605GL water recovery target.
It involves two projects, an $84m weir extension to stop the Mumbidgee River flowing in to Yanco Creek and on to the Murray River, and the rebadging of water to make it more accessible to downstream irrigators.
About 250 licence holders rely on the Yanco Creek system and have raised serious concern about their future access to water should the projects go ahead.
Report co-author and water consultant director Maryanne Slattery was "doubtful" the proposal would save any water - most likely it would cause more damage to the environment.
"The transmission losses they purport to save are actually natural and necessary parts of the water cycle," she said.
"Even the water agencies tasked with implementing these projects have said that benefits of the projects have been 'overstated' and that any 'savings are largely taken up delivering environmental flows back into the system they were saved from'."
The Australia Institute and Slattery and Johnson report states the water saved from Yanco Creek would remain in the Murrumbidgee and be turned into water entitlements.
"This water will no longer flow down the Yanco Creek system [and eventually into the Murray], but down the main channel of the Murrumbidgee," the report states.
"It is likely to encounter difficulties there, particularly given the increase in irrigation activity in the lower Murrumbidgee.
"In other words, water will be taken out of the Yanco Creek system, potentially denied to some Murray users and diverted into an entitlement with uncertain reliability."
Ms Slattery said the Yanco Creek "is one of the best managed parts of the basin", with irrigators paying a voluntarily levy to keep the system healthy.
"It is the ideal of a healthy, working creek system, but this is at risk," she said.
In its plan, the NSW government refers to the system as "effluent creeks", which Ms Slattery said gave "an idea of what they are planning for this region".
"If governments persist with these projects they will be leaving communities and taxpayers up the proverbial 'effluent' creek, without a paddle," she said.
"The Yanco Creek supply measures should be abandoned as they would damage this creek system and its communities."
The NSW government was contacted, but it did not respond by deadline.
The Murray Darling Basin Authority (MDBA) said the NSW government was leading the project.
"The MDBA's role is to reconcile the outcomes of the projects in 2024, and ensure the state governments take appropriate action should the projects fall short of Basin Plan requirements," a spokesperson said.