Worsening climate change will force farms and towns along the Murray and lower Darling rivers to live with 41 per cent less water within 20 years, a new CSIRO report says.
The report says food production and wetlands ecosystems will bear the brunt of change, with water diversions for irrigation projected to be cut by 30 per cent in South Australia, 32 per cent in NSW and 18 per cent in Victoria.
Dams, weirs and irrigation channels have already reduced flows to the lower reaches of the Murray including the dying Coorong wetlands and Lower Lakes by 61 per cent, with the region receiving no water about 40 per cent of the time, the report says.
It also refutes recent claims by Prime Minister Kevin Rudd that the deteriorating state of South Australia's Coorong wetlands the beautiful coastal setting for the film Storm Boy is solely due to climate change.
The CSIRO report warns, ''during the recent drought, South Australian irrigation allocations have sometimes been higher than current practice would recommend''.
It suggests the full extent of water extraction for irrigation may have been under-reported in South Australia, opening up the possibility that long-term water theft may be linked to the collapse of the Coorong.
Mr Rudd and the Federal Minister for Climate Change and Water, Penny Wong, visited the Hume Dam on the Murray River near Albury after the release of the CSIRO report on future water availability in the Murray River catchment.
Ahead of tomorrow's much anticipated government options paper outlining how emissions trading will work, Mr Rudd said yesterday that tackling the problems in the Murray-Darling Basin requires serious action on climate change.
''We have some real problems on our hands, and this report seeks to put some science around this in terms of defining the problem. And that's why we are here today. But, apart from defining the problem, our responsibility is to outline a course of action,'' he said.
But the director of the CSIRO's Water for a Healthy Country Flagship, Dr Tom Hatton, said yesterday that over-extraction had contributed significantly to the state of the Murray-Darling.
''Even if the climate isn't changing, we've changed the river. It would be up to our democracy, having done that maths, what they wanted to do about it,'' he said.
Mr Rudd said his Government was committed to three courses of action the enactment of a scheme to reduce carbon pollution, dealing with the over-allocation of water entitlements throughout the Murray-Darling Basin and improving the efficiency of irrigation systems.
''If we are going to deal with the long-term challenge of climate change, we need to act and we need to act with a clear-cut course of action.''
''Because what we are warned by the scientists is if we fail to act on climate change long-term, and we fail to act on the causes of climate change long-term, then what will happen to river systems like this is they will start to get worse,'' Mr Rudd said.
The Australian Greens' water resources spokeswoman, Senator Rachel Siewert, said the report showed the future for rural communities depending on the Murray River was grim if climate change trends continued.
''The Rudd Government is continuing to tinker around the edges of a problem that has enormous social and economic consequences for rural communities,'' she said.
''Massive changes are required and it's dishonest to everyone involved to pretend things can go back to business as usual. This is a crisis.''
Professor Mike Young, who holds the chair of water economics at the University of Adelaide, said the recent Council of Australian Governments meeting in Sydney showed Australia's political leaders had chosen ''more plans above rapid action'' and politics above vision.
''At a time when they should have empowered someone to solve this problem ... quickly, they have choked. The sad thing is, we already know the solution. It isn't rocket science. As the late [agricultural scientist] Peter Cullen said, it is really pretty simple housekeeping: How much water do we have to allocate?''
Inland Rivers System coordinator Amy Hankinson said the report showed that major wetlands and floodplain forests would bear more of the risk than other water users. Annual flood volumes to the Barmah-Millewa forest have already declined by 81 per cent and to the Hattah Lakes by 88 per cent, with further declines of 93 per cent predicted for both sites.
''Real action from the Federal Government on this issue is being stymied by the states and vested interests, and real leadership is required to cut through. Instead, the need to acquire water is being treated as a big money grab, with a market cap on water reducing the ability for willing buyers to find sellers.''
with AAP