South Australia is "fighting for what's right" by establishing a royal commission into the Murray-Darling Basin, Premier Jay Weatherill says.
Barrister Bret Walker is set to begin his investigation after the final terms of reference were gazetted on Wednesday.
He will examine the effectiveness of the existing Murray-Darling Basin Plan and whether it can deliver on its promise to ensure the system's environmental health and future as a sustainable resource.
The inquiry will also examine compliance from all states with the current plan and whether alternative arrangements need to be put in place.
Mr Weatherill marked the start of the commission by visiting Meningie, on SA's Lower Lakes where he says locals have been fighting for their fair share of the Murray water for years.
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"One of the first things I did as premier was stand up for the Murray and we secured 3200 gigalitres of water to deliver a healthy Murray-Darling Basin," the premier said.
"But we must always remain vigilant and it's clear some people upstream have been doing the wrong thing.
"Now it's time to stand up again and fight for what's right."
The premier announced the commission late last year after an independent basin authority review found NSW and Queensland were failing to make sure irrigators complied with water rules, a review sparked by reports of widespread water theft.
It has the support of the state opposition and South Australian irrigators while the federal government has indicated it will co-operate with the investigation.
Mr Walker is to present his final report to the SA government by February 1 next year but has discretion to hand down interim reports.
