Inflows to Wyangala Dam have been critically low since 2017 and it has been almost three years since general security water licence holders were issued an allocation.

And the Department of Planning, Industry and Environment (DPIE) has restricted general security carryover water - initially by 43 per cent last July, but that was cut in half again last week.

However, high security water has continued to be allocated, albeit reduced to a 70pc opening allocation this year and 87pc last water year.

Irrigators in the Lachlan Valley have argued the continued allocation of high security water, while general security carryover remains restricted, contradicts the rules laid out in the valley's Water Resource Plan.

Tom Green, Lachlan Park, Forbes, is chairman of irrigator group, Lachlan Valley Water and runs a prime lamb operation alongside his cropping business.

He has had to reduce his breeding stock by about 80pc because of the recent years of drought and lack of water available to irrigate his lucerne crops for feed.

He said irrigators were concerned by the methodology the DPIE was using to allocate water.

"The rules say you shouldn't make a new allocation to a licence without taking into account general security carryover.

"But, you can't have a lower priority licence overtake a high priority licence, so there's been a conflict between new high security allocations and the restrictions to general security carryover."

He said it appeared the DPIE was creating different systems every year to work out the share of water.

"I think there needs to be good guidelines in place so people can see what the restrictions will be if a forecasted scenario occurs, that way there are no surprises, the surprises are what hurts confidence."

Nick Turner, chairman of Lachlan Valley private irrigation corporation, Jemalong Irrigation, said with the restrictions to carryover, it was unlikely they would be able to provide an irrigation run this season.

He described the allocation of water in the valley as "policy on the run".

"They've used their own interpretation of the rules so there's uncertainty about how water will be shared between high security and general security carryover."

Lachlan Valley Water executive officer Mary Ewing explained that the chance of carryover being restricted increased when they went from a very wet period to a very dry period quickly.

"2016/2017 was a very wet year in the Lachlan so people went into that year with a lot of water in their accounts," she said.

"In 2016/2017 there was 1,495,000 megalitres of inflows to Wyangala but in 2017/2018 it fell to about 165,000ML."

A spokesperson for the DPIE responded to ACM's inquiry about this issue saying water allocations this year, as in every year, have been shared across high security and general security licences in accordance with the Water Sharing Plans and the Water Management Act 2000.

"The Act mandates that high security licences, like town water, be given higher priority for access to water over general security licences," the spokesperson said.

"For the 2020/21 water year there is around 97 gigalitres of general security account water, including 67GL already 'frozen' in accounts in 2019/20 and 30GL still 'active.'"