FARMERS will have to reduce the amount of water they take from the Murray-Darling by 30 per cent if the river is to return to an environmentally healthy state, the Wentworth Group of Concerned Scientists says.
In a report released in Melbourne yesterday, the Wentworth Group found that the Murray-Darling Basin would need an extra 4400 billion litres of water a year to protect wetlands, rivers, animals and plants in the dwindling basin environment.
That would return river flows to two-thirds their natural rate - the best chance of keeping all major rivers and wetlands healthy.
After including water recovered through government-funded buybacks and efficiency programs, Wentworth finds a 30 per cent cap for environmental water would deliver the additional water needed.
That would cost communities across the basin $2.7 billion in lost profits, which Wentworth recommends the government offer to rural communities as compensation through additional water buybacks.
Caps on water extraction from the basin have become a fiery issue and a major political battle is looming between the federal government and the opposition on water reform.
The Wentworth report is the first major attempt to quantify what type of cuts farmers should take to save the dwindling river system.
Caps - known as sustainable diversion limits - are currently being worked out by the independent Murray-Darling Basin Authority and will be the central part of a draft basin plan due out next month.
Wentworth Group director Peter Cosier said yesterday that now was the time to reform the Murray-Darling Basin.
''We have the money, we have the legislation, we have the river in trouble, and we have communities that need some certainty,'' he said. ''We can't waste this opportunity, now is the time to make the change and make the reform.''
National Farmers Federation president David Crombie, who has been a strong critic of the way sustainable diversion limits are being determined, dismissed the report, calling it a grenade thrown from the sidelines.
The Wentworth Group's proposal recommends modest cuts for 16 of the 18 catchment areas across the Murray-Darling.
But two rivers - the Murray and Murrumbidgee - would take massive cuts of 39 per cent and 65 per cent respectively under the proposal.
That would equate to cuts in profits of 12 per cent for the Murray region and 26 per cent for the Murrumbidgee.