The Australian Conservation Foundation and the Inland Rivers Network have sent the report to water ministers, pointing out that many large irrigation businesses in the north of the Murray-Darling Basin have water in their dams from summer floods and several of the properties are for sale.

But yesterday the Murray-Darling Basin Commission released its own water audit supporting the position of the Minister for Water, Penny Wong, that only rain can help the lower lakes in the short term because there is not enough spare water held in storage to help them.

Even those with water to sell agree that the amount available is just "a drop in the ocean" compared to what is needed.

Without the installation of major infrastructure it would also be physically impossible to return much of their privately stored water to the river system.

Only 350 gigalitres of water is set to be delivered to the lower lakes in 2008-09.

The commission estimates 1050 to 1250 gigalitres are needed to fill and maintain them in the same period.

Some have estimated that more than 1000 gigalitres are stored in private dams in the basin's north, but the commission puts it at 810 gigalitres.

The commission's acting chief executive, Les Roberts, said, "As little as 20 per cent of any water released in the north of the basin would reach the lower lakes … meaning that four or five times the water needed at the lakes would need to be released from that far upstream."

But the report from green groups says: "This proposal identifies six properties that could be purchased.

"They can provide at least 300 gigalitres in the short term to address the immediate crisis in the lower lakes … and over 400 gigalitres could be recovered each year on average for the Darling and Murray rivers for years to come."

The 28,000 hectare irrigation property Ballandool, on the Culgoa River in Queensland, has been on the market since 2006.

Its storages can hold 100 gigalitres but are less than half full.

Simon Southwell of Ray White Rural said Ballandool was a "$30 million-plus" property where the Government could keep the water licences and on-sell the land as a "magnificent" dryland farming property.

"The Government should have stepped in to buy it," he said.