WA farmers could be entitled to use the 7.5 billion litres of water sitting in the Logue Brook Dam after Harvey Water and the Water Corporation agreed on a water trade.
Last week both companies signed an agreement that would involve the unused water in the dam becoming available to irrigation farmers.
The proposal will be submitted to the Department of Water for approval but Harvey Water expected the trade would occur in the next month.
"This will enable farmers to know what water they have available to them when they develop their summer production plans," Harvey Water's acting chief executive Steve Iceton said.
Mr Iceton welcomed the signing of the agreement because very low winter inflow into the south west irrigation dams had meant that Harvey and Waroona irrigation farmers were facing allocations this summer of about 34 per cent of their full water entitlement.
Due to the circumstances facing farmers this summer Harvey Water had been looking at the corporation's unused water in Logue Brook.
"We were extremely keen to negotiate a trade to unlock the Water Corporation's allocation housed in Logue Brook because of the 2008 State Government decision to retain Logue for recreational use," Mr Iceton said.
"We are now very happy because by agreeing to this trade the corporation has provided us with the mechanism to ensure some farmers who are faced with a shortage of water this summer will have the opportunity to increase their allocation."
But Shadow Water Minister Fran Logan said Logue Brook Dam should never have been used for recreational purposes.
Mr Logan said Water Minister Graham Jacobs abandoned Labor's plan, to purchase the water from Logue Brook Dam in 2008 for drinking, which would have made extra water available this summer.
"In reality, the water was there for drinking purposes," Mr Logan said.
"Water Corporation had determined that water was very important if we went through a dry period, because they were expecting a dry winter and here we are in a dry winter and that water is not available.
"Despite repeated warnings and criticism, Minister Jacobs' first decision as Water Minister is to deny Western Australian's this vital water supply in favour of allowing water skiers to continue to use the dam for recreational purposes.
"Labor invested $16 million into the water trade program to secure the future of WA's water supply.
"The Minister's decision not to follow through with the plan is a slap in the face to taxpayers."
But Mr Logan said selling the water back to Harvey Water would assist farmers to deal with this year's low winter rainfall.
"Given this water has been for recreational use such as water-skiing for the past two years, it cannot be put into the drinking water system, so using it for agricultural purposes is appropriate," he said.
WAFarmers president Mike Norton said there was a possibility that some farmers might not be able to purchase the water because it could be too expensive.
"It will depend on the value at auction to whether it's financially feasible to purchase the water," Mr Norton said.
"The Agriculture and Food Department in Harvey is developing a computer model so that farmers can add the various costs of water versus hay and dry seeders, as to what value they can afford to put on the water that's going to be auctioned.
"At least they've got access to the water, but the next thing is to work out what value that water makes at auction, then the farmers need to work their own numbers to see whether they can make money out of it."