UNCERTAINTY on water allocations and grape prices has left winegrape growers little ability to plan for the upcoming season, according to Murray Valley Winegrowers.

A water allocation of 13 per cent in the Victorian Murray Valley, 80 per cent in the NSW Murray Valley and little information on what allocations will be available in summer has left harvest planning for many growers in tatters, according to MVW chief executive Mike Stone.

Mr Stone said an allocation of 13 per cent for the Victorian Murray Valley and increasingly warmer weather meant growers now had to think seriously about buying supplementary water, which has been trading at around $500/megalitre.

"Many growers are without the financial means to make this investment, but those that can need to know likely grape prices to assist with budgeting and loan applications," Mr Stone said.

"They need to know whether investing in extra water will be viable and to make that call they need to have a good idea of grape prices."

Mr Stone said State Government must tell growers if the rebate scheme for fixed water charges would be available in the 2007-08 season, while wineries needed to start negotiations with growers to decide on prices for the 2009 harvest.