WaterNSW will release more water from Menindee Lakes to make space for the massive inflow of water coming down inland rivers.
Downstream communities have welcomed the decision but said it should have happened much earlier because crucial farmland and wetlands were crying out for water.
Water equalling another five Sydney Harbours is expected to flow into Menindee Lakes in the next couple of months.
WaterNSW spokesman Tony Webber said there had been several exceptional rain events in Queensland and across New South Wales to the upper reaches of the Barwon-Darling.
"That's changed our calculations, moves us to a flood operations mode, and lets us increase the releases," he said.
The amount of water will increase from 18 gigalitres a day up to 23GL from Friday, which will cause some flooding in Menindee.
WaterNSW will work with the Bureau of Meteorology to monitor inflows and river heights, and the NSW State Emergency Services to manage flood impacts.
It was estimated about eight to 10 properties would be affected, including issues with access roads, but at this stage WaterNSW did not believe homes would be flooded.
"Nonetheless, it's inconvenient for people," Mr Webber said.
"We think we'll hit that 23GL/day in early June and those releases as they occur won't be immediately felt downstream, so it will give people the opportunity to take what steps they need to protect their property to make other arrangements."
Water needed downstream
Meanwhile, environment groups and graziers have said more water should have been released earlier to allow critical wetlands as well as productive farmland to flood.
Mel Gray from the Nature Conservation Council said bigger water releases were needed to get the river up over the banks and onto the flood plains.
"Because that's what triggers native fish breeding and that's what is going to protect stands of red gum and black box that won't be able to withstand the next drought if they don't get a flood now," she said.
Farmers want bigger flows too
Farmers downstream are also relying on the water to set them up for cropping and grazing for the next few years.
Grazier Angus Whyte has a property that is adjacent to the Anabranch/Talyawalka River, which is in the Lower Darling.
He said a good flood is really needed after large sections dried up in 2019.
"Every centimetre over the high flow level of 18,000 megalitres a day results in more floodplain being inundated, more trees and plants watered, more food for river life, fish, frogs, yabbies and turtles," Mr Whyte said.
Water releases kept low
WaterNSW has been releasing water from Menindee since December last year.
It started at the rate of 23-25GL/day, a rate that would have resulted in water spilling over the banks of the main channel of the Great Anabranch and into thousands of hectares of parched flood plain.
But four days later, on December 20, WaterNSW cut the release volumes to 18GL/day.
Mr Whyte said that was due to concerns expressed by the State Emergency Services (SES) about possible inundation of some river shacks.
"I express no ill-feeling towards anyone in the SES," he said.
"The question I have is, why do we say that our man-made property trumps the environment every time?"
'Not enough time', say residents
Locals have questioned why it has taken so long for WaterNSW to act, given that there have been heavy falls upstream for months.
Menindee resident Graeme McCrabb said he believed the town of Menindee had been forgotten about.
"I think three days notice for people who might be away or have stock to move, is just not good enough," Mr McCrabb said.
"We're in 2022 not 1922."
Mr McCrabb believed it was inevitable even more water would need to be released, despite WaterNSW currently setting the cap at 23GL/day.
"In the next few months, whatever comes over the Wilcannia weir has to go down the river, so there's no controlling that," he said.
"That's just in the hands of the gods.
"The rainfall predicted going forward for the next two or three, or even six months, is staggering, so we could be in a world of hurt here.
"There's been just no thought to planning for that."
