Farmer representatives are backing the Victorian government's move to put a lid on the impact of the booming nut industry in the southern Murray Darling Basin, and urging other states to follow suit.
Victorian Water Minister Lisa Neville announced last week there would be no increase to irrigation extraction in the lower Murray region, below the Barmah Choke, for the next 12 months.
Her policy is a response to the recent boom in thirsty permanent plantation nut crops that has driven irrigation demand so high in the southern Basin that the price of water may become unaffordable for rice, dairy or even cotton irrigators.
The new plantations are concentrated in the lower Murray, far away from established irrigation districts, and getting the water that far down the system incurs much greater losses than delivery for entitlements in traditional dairy and cropping districts.
"We have to make sure the risks to the environment and Victorian entitlement holders don't increase due to more extractions - that's why I will personally review all licence applications for the next year," Ms Neville said.
Ricegrowers Association president Jeremy Morton said the rising demand from permanent plantings, which requires the bulk of their water entitlement to come in a lump at the start of the season, strained the river system beyond its capacity.
"The issues are largely below the restriction in the system (at the Barmah Choke). It's about the physical capacity of the system and being able to get the water to the users when they want it, and the volume they require.
"The impact on all irrigators is it takes more water to deliver a megalitre further down the river and by definition that means there is less water available to everyone."
Responding to rising concerns, the Almond Board of Australia called in May for a rethink of water allocations.
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"We were calling for a moratorium, pending a full review, which is what Lisa Neville is suggesting," said Almond Board chief executive Ross Skinner.
"What we were concerned about was the deliverability of water and the issuing of new licences (using that as a generic term). Before new licences are issued we want to know whether there is capacity to deliver during the peak of the irrigation season."
The Victorian Farmers Federation water council chairman Richard Anderson said the market review must cover water trading rules and urged other Basin states and the Murray Darling Basin to contribute.
"The new modelling and review of water trading rules must be an urgent priority for the MDBA," Mr Anderson said.
"It is critical that NSW and South Australia take action now so we can collectively put a pause on the rapid expansion of water licences, review water trading rules, and then decide how to move forward in a way that protects everyone.
"Careful management of water licences in the lower Murray will not only protect irrigators in that section of the river, but also farmers in the Goulburn Murray Irrigation District that have had a large amount of their water traded downstream."
Mr Morton said inter-valley trade rules "aren't fit for purpose" and policy makers who developed them years ago had not envisioned some of the problems which are now biting.
"If the purpose of them was to manage how and where water was used, then it doesn't seem to have worked," he said.
"There was a failure to deal with where the water use might shift to in the future and whether the pattern of use might change from winter, spring or summer, whenever the demand was.
"They generally thought that if water use did shift it would move closer to the dams, because that's more efficient. But the other part of that is the land is already developed there, and it can be expensive.
"If someone wants to develop a new enterprise they will look downstream for the large contiguous plots close to the river."