Ms McKenzie moved a motion on Wednesday to amend a government bill so 450 gigalitres of water would not be required to be returned to the environment and the Commonwealth would not be allowed to buy back any more water rights from irrigators.

The move, which marked a split from the Liberals, came just two days after Barnaby Joyce was returned as Nationals leader and deputy Prime Minister.

Ms McKenzie is expected to be promoted to the cabinet under Mr Joyce.

"For too long our Basin communities have been hurting," she said.

"The science is now telling us the approach adopted 12 years ago is outdated and the plan must change."

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Greens and Labor criticised the move, with South Australian senator Sarah Hanson-Young saying Mr Joyce had 'launched war on South Australia and the Murray Darling'.

However, the Nationals' action had been welcomed by Blightly farmer and Speak Up 4 Water chairman Lachlan Marshall.

"I think it shows they're listening to the community voice because for a long time we've been saying [their talk] means nothing unless legislation is amended," he said.

"What is means is that attitude of 'just add more' comes to an end.' The basin plan is basically predicated on bad science that says the more water you jam down the better things will be and that's failed spectacularly.

"We need to be smarter with resources and more efficent with the resources we have to deliver much greater benefits."

Barmah residents and speak up deputy chair Lloyd Polkinghorne said a proper review of the Murray Darling Basin Plan was needed.

"We've lost five to seven metres of Murray Bank here in Barmah in eight years," he said. "If we've got a plan to save rivers and help rivers it should be doing that not destroying what we've got."