Environmental organisations have slammed the Murray Darling Basin Authority for compromising on water flows.
Following public backlash and political pressure resulting from its initial proposal to withhold 3000 gigalitres to 4000gL of water for environmental flows, the MDBA is now proposing a figure of about 2800gL for its upcoming basin plan.
The authority is also seeking to reduce that by a further 890gL, citing "water volume that accounts for a history of effort", in recognition of buybacks and improved infrastructure, leaving a figure of about 1910gL by the year 2019.
But 10 environmental organisations from all four MDB states have condemned the proposal, saying the South Australian floodplain would be written off and a legacy of salinity, acidification and species extinction would be left for future generations.
This includes Australian Floodplain Association president Mark Etheridge, who said non-extractive agriculture would lose under the plan.
"Floodplain grazing and opportunity cropping are significant contributors to the economy and they rely on natural healthy river systems to survive," he said.
Other groups included the River, Lakes and Coorong Action Group, the Queensland Conservation Council, Environment Victoria and the Nature Conservation Council of New South Wales, which called for a minimum of 4000gL to be maintained for the environment.
MDBA chairman Craig Knowles said the new figure was based on the latest modelling and left room for schemes that would result in better water flows.
This included 'adaptive management' to create flexibility as developments took place, using local knowledge to implement water savings, and incorporating recommendations of the Tony Windsor review to update State water management rules dating back more than 100 years.
"This is about more than just a volume of water," Mr Knowles said. "It's how you run the river, how you recognise its restraints, and recognising that what we're doing at this point is just one more step in a pretty long story that started years ago."
With a target of 955GL by 2015, the plan would also leave room to either increase the remaining target of 955GL by 2019, or reduce it, depending on progress.
But SA Murray Irrigators committee member David Peake said the authority should start with its original worst case scenario so it can work down, rather than upwards.
"This idea of starting low and then going up or down is worrisome," he said. "There's only one way to go, and that is down, and we can't work any lower than 2800gL.
"I'm an irrigator, but I'm also for the health of environment too, because without that, we're all doomed."
State River Murray Minister Paul Caica said the plan should be based on peer-reviewed science and should not represent a "political fix".
He said the Goyder Institute for Water Research review – commissioned by the State Government – found environmental flows of 3500gL to 4000gL was most likely to be required for the Chowilla floodplain and the Coorong, Lower Lakes and Murray Mouth.