There may be no federal royal commission into the Murray-Darling Basin Plan, but South Australia's version will be the next best thing, says state Water Minister Ian Hunter.
Barrister Bret Walker, an expert in constitutional law, will head the state-based investigation when it begins early in the new year.
Mr Hunter said he was confident the royal commission would have the power to call witnesses and demand evidence from interstate lines.
"There will be an extra-territoriality to the royal commission because the River Murray is connecting states," he said during a visit to Murray Bridge last week.
But he said there would be no need to compel people to come forward, as a number of interstate parties including primary producers and ex-public servants had already indicated they would give evidence.
The royal commission's draft terms of reference focus on whether the basin plan is likely to achieve its goals; the likely impact of illegal activity or non-compliance upstream; whether the enforcement and compliance powers available to governments are up to scratch; and whether the plan properly accounts for climate change, among other matters.
Mr Walker will deliver a final report by February 1, 2019.
In a statement, Premier Jay Weatherill said his government would take legal action after that if necessary.
"If evidence emerges of criminality, we'll have no hesitation in pursuing the perpetrators," he said.
"And if South Australia can demonstrate loss as a consequence of this misbehaviour, we will pursue our civil rights."
Andrew Curtis, the chief executive officer of the South Australian Dairyfarmers Association, said he supported Mr Hunter's efforts to keep the pressure on.
But he said the state's dairy industry would take a wait-and-see approach to the royal commission.
"We have some concerns ... around the ability for it to deliver what some people hope it'll deliver," he said.
"We recognise there are inconsistencies and inefficiencies in the way the whole Murray-Darling system works, but a lot of the folks are in other jusisdictions.
"We take the minister at his word in that he believes it can go far enough, but we still have some concerns others won't play ball."
Monteith dairy farmer Glenn Dohnt said he hoped the royal commission would help deliver the outcomes promised when the basin plan was finalised in 2012.
He said his family’s property had experienced strong growth since the 2009-10 drought and he did not want it put at risk.