Raising the amount of water returned to the environment to 3200 billion litres a year and finding ways around the flooding of private property, bridges and roads could significantly boost the health of the Murray Darling basin's wetlands and flood plains, new modelling has found.
The latest research by the independent Murray-Darling Basin Authority (MDBA) has found that relaxing so-called ''constraints'' by allowing more water through dams and finding ways to stop flooding of infrastructure and private property could greatly help the environment of the lower basin.
But, crucially, it finds there would be only marginal benefits for key South Australian sites such as the Murray Mouth, Coorong and the Lower Lakes.
South Australian premier Jay Weatherill has vowed to push for the additional water.
"We have always known that the proposed 2750 billion litres was simply not enough for a healthy river," he said.
"Today we have been shown 450 billion reasons why we have fought for the Murray and why will keep fighting for it."
The authority's current Murray-Darling rescue plan involves returning 2750 billion litres to the environment - a figure green groups say is not nearly enough - mostly by buying back irrigators' water rights. Environment Minister Tony Burke is racing to have a final plan that he can put to the federal Parliament by the end of the year.
The authority's latest report found that boosting the total to 3200 billion litres and easing the constraints could lift the water flows through the Lower Murray and Darling River junction from 60 billion to 80 billion litres a day.
This ''could be of critical importance to the long-term sustainability of vegetation communities'', the report finds.
But it notes that it is harder to help regions further up the river basin as this would ''involve a much greater degree of flooding risk''.
It could benefit areas such as the Barmah-Millewa Forest in southern NSW, the Hattah Lakes in north-west Victoria and the Riverland-Chowilla floodplain in western South Australia.
But it notes that there would be a considerable cost involved. It would ''require a commitment and significant investment from both state and federal governments''.
Crucially it also finds that there would be little benefit for key South Australian areas, saying the ''overall results were not significantly changed''.
New South Wales Irrigators Council chief executive Andrew Gregson said the latest modelling had placed the process "entirely in the realm of the absurd."
"The report concludes in relation to the lower Lakes and Coorong that the overall results were not significantly changed by increasing from 2750 to 3200 - this model run was driven by the SA premier," he said.
"The report has now conclusively told him that it won't benefit his Lakes - so perhaps he might finally stop bleating and the rest of us can get back to ensuring a balanced Basin Plan."
SA Liberal MP Tim Whetstone said social and economic impacts of the new modelling were unknown.
“The question left unanswered is what this means for South Australia’s sustainable diversion limit,” Mr Whetstone said.