South Australia's lower lakes are likely doomed because of water over-allocation and drought, a Senate committee report has found.
The report found the federal government may have to resort to flooding the freshwater lakes with salt water to save them.
"There is not enough water in the system," the Senate committee's report said.
"This is the result of historic over-allocations, the current unprecedented drought, and the emerging impacts of climate change."
The report, endorsed by Labor senators, was non-committal about flooding the lakes with sea water to keep them functioning.
"If the admission of sea water becomes necessary, the potential environmental impacts should be subject to further detailed investigation and community consultation," committee chair and Labor senator Glenn Sterle wrote in the report.
The report's findings were described as overly pessimistic by committee member and Australian Greens senator Sarah Hanson-Young.
"The government's report has basically dismissed the evidence that was given to the inquiry," Senator Hanson-Young said.
"The evidence given shows there are things we can be doing to ensure the survival of the lower lakes and the Coorong and give the communities in that area some hope."
Federal Climate Change Minister Penny Wong said the report showed how grim the situation is in the Murray Darling Basin.
"The evidence presented to the inquiry indicated there is very little fresh water available right now for either the lower lakes or for the numerous other icon sites throughout the basin," Senator Wong said.
She said the danger of acidification of the lakes had been delayed until well into next year because of recent rains, but that did not avoid the need for an enduring solution.
Senator Hanson-Young said 60 gigalitres of fresh water was needed to secure the future of the lower lakes, and it was available for allocation within the southern areas of the Murray-Darling Basin.
"We know that all we need now is 60 gigalitres of fresh water to avoid the crisis situation we were going to be facing," she said.
"We know the water is there .. what we need is the political will," Senator Hanson-Young said.
SA's independent Senator Nick Xenophon, another committee member, also said the lakes could be saved.
"If we had one river system with one set of rules, we could ensure an equitable share of water for irrigators and the environment," Senator Xenophon said.
"Right now we have a situation where the eastern states basically take what they like, and South Australia is left facing an economic and environmental disaster."
Liberal environment and water spokesman Greg Hunt said the report findings were an indictment of wasted months.
"The report highlights the folly of the irresponsible delays in carrying out urgent infrastructure works in the area by this (Rudd) government," Mr Hunt said.