At least 148 billion litres will be released, meaning South Australia's Lower Lakes will have a temporary reprieve from completely drying out and becoming saline.

"NSW and South Australia have been working co-operatively to make sure the Lower Lakes are given a reasonable flow from the water from recent floods," the Premier, Kristina Keneally, said after a meeting of the Murray-Darling Basin Authority yesterday.

Most of the floodwater is still winding its way south along the Darling River in western NSW.

Some has been allowed to fill the once dry Lake Pamamaroo and Lake Wetherell, though neighbouring Menindee and Cawndilla lakes have been sealed off by locks and channels to let more water flow downstream. When the lakes are full they are home to more bird species than Kakadu National Park in the Northern Territory.

The floodwater has also meant some farmers along the Darling can access their full water allocations for the first time in years.

Ms Keneally said the exact volume of water in the flood was not yet known, but the states had agreed the minimum amount of 148 gigalitres could be spared.

The flows are expected to keep the ailing South Australian lakes above their survival minimum for a year.

"Right now a majority of the water from recent rainfall is still making its way downstream from north-west NSW,'' Ms Keneally said. "This water has to travel hundreds of kilometres downstream to the Menindee Lakes before it can be released. In the coming weeks we'll have a better understanding of how much water has reached Menindee Lakes after travelling from north-west NSW.

The South Australian Premier, Mike Rann, said: "The extra water will ensure that, even if record low flows continue throughout 2010, we will maintain water levels in the Lower Lakes above the critical levels necessary to avert further environmental damage."

He said the flows would reduce the risk of acidification, lower salinity levels and improve the habitat for wildlife.

A Senate committee report in 2008 found the lakes and nearby Coorong region were in danger of becoming acidic because of poor water flows.