The announcement that 148 gigalitres of water will be released from NSW to the lower Murray River and Lower Lakes is welcome, but it doesn't let the Federal Government off the hook, according to Greens Senator Sarah Hanson-Young.

Senator Hanson-Young, Greens Spokesperson on the Lower Murray, says Prime Minister Kevin Rudd did little to help resolve the conflict between the states on how much water would be released to the bottom end of the river, and that his government's attitude needs to change.

"The 148 gigalitres of water will be is a welcome reprieve for the Murray and Lower Lakes, but it doesn't mean the Federal Government can relax,'' Senator Hanson-Young said.

"South Australia will receive one-eighth of the floodwaters, after NSW irrigators receive everything they wanted - this just shows we need to change the way water is managed in this country.''

For decades, the Murray has not been guaranteed the environmental flows it needs, and the Greens believe that a system that does not compel the states to act co-operatively on water is to blame.

"We shouldn't have to beg for every drop of water the River, Lakes and Coorong needs, and we can't keep relying on the whim of the states to keep the whole of the river alive,'' Senator Hanson-Young said.

"Kevin Rudd must establish - as soon as possible - a national independent authority with the powers to make decisions in the best interests of the river, regardless of state vetos.''

The Greens have always opposed the Wellington Weir in South Australia, and are pleased that the Rann Government has said that the new inflows will allow the weir's construction to be postponed for a "significant'' time.

"If 148 gigalitres of water can put the weir off for 18 months or two years, then surely the Federal Government can scrap the whole proposal by ensuring an adequate environmental flow,'' the Senator said.

"The Rudd Government has hidden its inaction behind the excuse that it couldn't make it rain.

"Well now it has rained, and the heavens opening have given the Government a narrow window of opportunity to get things right once and for all - our environment cannot continue to be left at the bottom of the agenda.''