Victorian high reliability water share irrigators could face zero allocations, this year.
The total amount of water stored in the Murray-Darling Basin's dams has dropped below 30 per cent for the first time, since May 2016.
Murray Darling Basin Authority River Operations manager Andrew Reynolds said continuing dry conditions would have a significant impact on Victorian and NSW irrigators.
"If things stay dry, Victorians with high reliability water shares in the Murray catchment are facing zero allocations at July 1, 2019," Mr Reynolds said.
"We need wet conditions to prevail for entitlement holders to reach full allocations by October," Mr Reynolds said.
"The New South Wales outlook also includes indications about the effect on allocations if dry conditions continue."
In the Murrumbidgee and Murray, for example, at this stage no commencing general security allocation for 2019-20 was expected.
"Across the Basin we have 6932Gigalitres of water in storage right now, which translates to 30pc capacity," Mr Reynolds said.
"This time last year storages were at 52pc."
Mr Reynolds said while 30pc storage was a concern to water managers across the Basin, the southern basin was in better shape than the north.
What is widely regarded as the southern drought reserve, Dartmouth Dam currently held just over one third of the water, stored in the entire Basin.
"In the northern Basin, the dams are at only 11pc capacity, with 569GL available of a possible 5198GL.
"Again, the reserves in northern dams themselves vary-Lake Wyangala on the Lachlan, for example, is holding 33pc with 400GL while Split Rock Reservoir on the Namoi is about 4pc full with 14GL.
Mr Reynolds said the MDBA didn't know how long the drought would last, and continued to plan for the possibility that storage levels would be a concern into next year.
"It is usual for reserves to be drawn down every year at the end of the irrigation season, with the expectation that water availability will increase as winter and spring rains top-up the storages," Mr Reynolds said.
"In the past year those rains have not eventuated or have been very limited.
"The last time we had similar conditions was in autumn 2016, when Basin-wide storage levels bottomed out at 28pc, before recovering to 84pc, six months later, following widespread rain in the southern Basin.
"With dry conditions expected through autumn, we're anticipating people will carry-over water where they can to shore up their supply into next year
"In the Murray we will continue to notify the state water authorities about the availability of water, as they consider their allocation position for next season.
"We're keeping a constant eye on what's happening and we're working with the state governments, the Bureau of Meteorology and local communities to make sure we have the best possible information to guide water management as the year progresses."