The future of the Murray-Darling Basin Plan is unclear, with states at an apparent impasse ahead of Tuesday's Ministerial Council meeting of water ministers.
Southern basin irrigators have described the meeting as "the most critical in the history of the Murray-Darling Basin Plan".
Earlier this month during the Convoy to Canberra, federal Water Minister David Littleproud agreed to ask his state counterparts to give basin interim-inspector general Mick Keelty the power to investigate the impact of the plan and other water-sharing agreements.
Speak Up campaigner Shelley Scoullar said the move would give irrigators some much-needed confidence, while Convoy co-organiser Darcy Hare said it would allow Mr Keelty "to find buckets of water that are locked away and not utilised due to archaic rules", which could provide relief to farmers and communities.
Ms Scoullar said while it wasn't ideal, southern irrigators would support NSW's decision to walk away.
"Certainly southern NSW and northern Victorian food producers have nothing to lose, it can't get any worse," she said.
But the National Irrigators' Council has warned the NSW government's decision to walk away from the plan could cost communities along the Murray and Murrumbidgee rivers more than $1 billion.
NIC's chief executive Steve Whan said NSW's decision to leave the plan could be damaging for communities.
"The plan itself is federally legislated, if NSW walks away it doesn't take away the law that says the federal government is obligated to recover 2750 gigalitres of water across the basin for the environment," he said.
Mr Whan said 650GL of the 2750 GL total can be delivered through programs which deliver equivalent environmental benefit rather than through buy backs.
He said the commonwealth was obliged to recover or deliver programs equivalent to 287 billion litres of water from the Murray and Murrumbidgee rivers. Mr Whan estimates that water is worth more than $363 million in crops and more than a billion dollars to the region's economy.
"If NSW walks away work stops on those projects, which might mean come 2024 the federal government comes in and buys 650GL from the market," he said. "It could have severe negative impact on irrigation communities."
Mr Littleproud said pulling out of the plan would "not return one drop of water to NSW farmers" and the government would need to recover the final 20 per cent, rather than investing in infrastructure to recover it.
Victorian Water Minister Lisa Neville said she supports the establishment of a formal Office of the Inspector General but the review of water sharing arrangements "seems to have come out of nowhere".
She said changes to water-sharing arrangements which pre-date the basin plan would penalise Victoria.