SA Water Minister David Speirs says federal Labor's plans to make changes to the Murray-Darling Basin Plan are cause for concern, as "SA will suffer the most as a result".
His comments follow federal Labor environment and water spokesman Tony Burke's announcement last week that if his party forms government, it would scrap the deal to deliver 450 gigalitres of 'upwater' to SA and remove the 1500GL cap on water buybacks in the MDB Plan.
In December, the federal and basin state governments signed an agreement to send 450GL of environmental 'upwater' to SA, with water recovered through efficiency projects. A key condition of the deal - advocated for by the Vic and NSW governments - was that there be only neutral or positive socio-economic outcomes of recovering this water.
Labor has announced it will restore the original socio-economic definition for delivering the 450GL to the system.
Mr Burke - the former federal Water Minister that passed the Basin Plan into law in 2012 - maintains upwater should be recovered through buybacks.
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SA opposition water spokesperson Susan Close said "federal Labor has come through for SA and for the river".
"Cancelling the cap on voluntary water buybacks and overturning the overly complex criteria for water efficiency projects is our best part to getting SA the water we need to keep the river healthy," she said.
But Mr Speirs is concerned.
"The MDB Plan is the only plan we've got, there is no Plan B," he said.
"Tony Burke's populist announcement will simply blow up the plan and SA will suffer the most as a result.
"After the historic December agreement, NSW, Vic and the ACT are working towards projects that will deliver real water to the river.
"If this agreement is overturned, it puts $70 million of funding for the Coorong in doubt and throws away a pathway to achieve 450GL of environmental water."
SA Murray Irrigators chair Caren Martin believes the federal Labor Party is just playing politics when it comes to proposals of changing the implementation of the MDB Plan.
"I believe they are beating up an issue where there really isn't one," she said.
"Their suggestions don't really affect the overall intent of the plan - the figures stay the same, the 450GL of upwater will still need to be recovered, it's just the 'how' that Mr Burke is trying to change.
"Really he is just trying to revert the plan back to the way it was formed in 2012, but there has been a lot of politics since then."
Ms Martin said the proposal to lift the cap on water buybacks only showed a lack of confidence in their water-saving projects.
"If their modelling is wrong, or their delivery partners are inept, then questions need to be asked," she said.
Darling River Action Group vice-president Darryn Clifton, Broken Hill, NSW, believes buybacks will only be useful if they came from the Northern Basin.
"But they need to have minimal impact on irrigation communities," he said.
Mr Clifton believes long-term river connectivity should be the priority of any adjustments to the plan, which should include highly-regulating water extraction in the Northern Basin and creating a federal authority that controls the water within the basin.
"Decisions should not be left up to the states to squabble over," he said.
"The entire MDB also needs to be regulated, particularly floodplain harvesting, to ensure better water equality across the basin states."