Southern New South Wales water users say they plan to fight flood plain harvesting legislation in court, arguing it will have a detrimental impact on downstream flows.
The call follows the practice becoming legislated in two northern NSW Murray-Darling Basin valleys after close to two decades of debate.
The NSW Environment and Water ministers signed off on amended water sharing plans on Friday, meaning irrigators in the Gwydir and Border Rivers valleys will be required to meter and pay for flood plain harvested water for the first time.
Flood plain harvesting allows irrigators to capture water during floods using levy banks, diversions and pumps.
In northern NSW, it is a crucial water source for irrigators because unlike southern NSW, there are few large public storage dams.
However, Southern Riverina Irrigators vice-chairman Darcy Hare said too much water had been licensed for the practice, reducing inflows downstream and putting their water security at risk.
"There's going to be more onus put on … all of those southern basin rivers to make up the shortfall for what will no longer be coming down the Darling River," Mr Hare said.
Mr Hare said they planned to challenge the legislation in the Supreme Court, arguing the amount of water licensed exceeded legal limits.
"We will not be giving up here by any means," he said.
A spokesperson from the NSW Department of Planning and Environment said the government was confident water sharing plans were made lawfully.
They said flood plain harvesting policy reduced the practice to legal limits, including the 1994 cap, and that flood plain harvesting in the northern basin had very little impact on flows in the southern basin.
Flow targets introduced to help protect downstream
Flood plain harvesting regulations have been disallowed by the NSW Upper House three times, with some MPs questioning the legality of the practice and voicing concern for downstream interests.
To help alleviate these fears, NSW Water Minister Kevin Anderson introduced flow targets to flood plain harvesting rules, meaning a certain flow had to be reached downstream before irrigators were allowed to start flood plain harvesting.
"Among these rules, we're proposing that restrictions will apply to flood plain harvesting licences when the water volume in Menindee Lakes drops below 195 gigalitres — these are the first restrictions of this type anywhere in the Murray-Darling Basin," Mr Anderson said.
"These rules, together with proposed temporary water restriction triggers, will ensure upstream water take, including flood plain harvesting, is balanced against downstream critical human and environmental needs."
However, NSW Greens MP Cate Faehrmann labelled the legislation "disastrous" for downstream communities.
"They have licensed an extraordinary amount to both the Border Rivers and Gwydir Valley systems," Ms Faehrmann said.
"What they have licensed is essentially the death of Menindee Lakes."
Reality sets in for northern irrigators
Northern NSW irrigators have long supported the legislation, but Gwydir Valley Irrigators Association president Zara Lowien said it would have an estimated $90 million economic impact on the region.
"Now the reality of that sinks in that the majority of our irrigators having 40 per cent less access to floodwater as a result of that reform," Ms Lowien said.
"It's like, irrigators have been encouraged to … build on-farm storages, as someone might be encouraged to build a house, and we've just been told we can only use 60 per cent of that house in some cases.
"That's going to take some adjustment but at the end of the day, it was an environmental reform that had to happen."
The NSW government has said flood plain harvesting framework will be fully operational in the Border Rivers and Gwydir valleys by September 1.
While, licences for the Macquarie, Barwon-Darling and Namoi valleys will be determined and will come into effect later this year and in early 2023.
