South Australia's Murray-Darling Basin Royal Commission delivered a scathing review of the plan for the basin and accused Commonwealth officials of gross maladministration, negligence and unlawful actions.

Key points: A law expert says the Murray-Darling Basin Plan is on a knife edge

A law expert says the Murray-Darling Basin Plan is on a knife edge The uncertainty follows a scathing royal commission report into the plan

The uncertainty follows a scathing royal commission report into the plan It is not the first time the basin plan has faced a potential crisis

Commissioner Bret Walker SC reported that the original architects of the plan were driven by "politics rather than science" when it came to setting environmental targets.

As the aftermath of the report continues, here's a look at what could happen next.

The plan is on a knife edge

University of New South Wales constitutional law expert George Williams said the plan was now in limbo.

"If any one state was to seek to pull out, that could destabilise the agreement, could jeopardise parts of the legislation and its operability, and also give rise to the prospect of legal uncertainty and challenges," Professor Williams said.

"These really are uncharted constitutional questions about what happens when these agreements fall apart.

"We haven't had something like this occur before in Australian history of this magnitude."

Have there been threats to the deal before?

It is not the first time the basin plan has faced a potential crisis.

Less than a year ago, NSW and Victoria both threatened to walk away from the deal when proposed changes to reduce the amount of water being returned to the environment were blocked by the Senate.

In 2012, former South Australian premier Jay Weatherill told government lawyers to prepare a High Court challenge because of concerns the plan would not deliver enough water to wetlands.

Five years later, Mr Weatherill's government launched a royal commission following allegations of water theft by NSW cotton farmers, which first aired on Four Corners in 2017.

Will the Federal Government conduct its own royal commission?

Yesterday, Federal Agriculture and Water Minister David Littleproud said it was "way too early to make an assertions" about whether a separate authority was needed to regulate the plan, but ruled out the need for a national royal commission into the basin.

"This was a royal commission predicated in South Australia. The basin obviously goes further than South Australia," Mr Littleproud said.

"But we respect what the commissioner has done — he's done a significant body of work here that should be respected and looked through."

Today, Prime Minister Scott Morrison said it was important to "maintain bipartisanship" and for the people "on the ground" who run the plan to work without distraction.

"I don't want politics to distract them," Mr Morrison said.

"I want them to be able to get on and do the job and I'm going to do my part to make sure the Murray-Darling Basin Plan remains a bipartisan plan."

A map of the Murray-Darling Basin in Australia. ( ABC News: Ben Spraggon )

Shadow Environment Minister Tony Burke said he was alarmed by the findings and wanted to know more details about the behaviour described in the report.

"We are calling for the findings that have been made in the royal commission to be referred to the Australian Public Service Commissioner so there can be a proper investigation," he said.

"If these findings are right then serious action needs to be taken by the Commonwealth and if those findings are based on the fact that not all the evidence was before the commission then those people need to have their names cleared."

Last month, Greens Senator Sarah Hanson-Young called for a national royal commission on the Murray-Darling Basin.

This morning, she called for the authority's chief executive Phillip Glyde to resign.

"It's time for him to step down, for a new head to be put in place, someone who can restore confidence and put the environment back at the centre of the process of saving the river," she said.

Could there be a High Court challenge?

The legal basis for the Murray-Darling Basin Plan is a complex one that involves competing state and federal powers.

The 2007 Water Act was signed into law in 2012 and established the Murray-Darling Basin Authority (MDBA), which oversees the implementation of the basin plan.

"The real problem with the Murray-Darling system is that at Federation power over that system … was not given to the Commonwealth, instead it was left with the states," Professor Williams said.

Professor Williams said Commonwealth commitments to international environmental treaties played a crucial role in sustaining the basin plan.

"The two key ones here are the Convention on Biological Diversity, and the Ramsar Convention on wetlands," he said.

"When the Water Act was designed it was based upon implementing international conventions that are about environmental protection and as a result it means that any plan for the basin must give precedence to those environmental considerations.

"If indeed it turns out that the plan does not faithfully implement those environmental considerations, then that's been the basis upon which some people have contemplated a High Court challenge."

Professor Williams said it was unclear if the basin plan would survive a High Court challenge.

"I again think there are good arguments that it could, but that's really untested," he said.

"That would come down to whether the Murray-Darling Basin Plan faithfully implements the environmental considerations set out in international conventions."

Who could launch a High Court challenge?

The most likely scenario would be for irrigators or environmental groups, rather than states, to challenge the basin plan on constitutional grounds.

In 2012, a group of 500 irrigators from across the basin tried to do just that before the High Court rejected their attempt.

However, another constitutional law expert, University of Adelaide's John Williams, said the royal commission could provide grounds to take a case further.

"I don't think there's any trouble in finding someone to do it," Professor Williams said.

"People will head to the High Court when the politics of this fails.

"That's been the history of Australia — people don't go to the High Court as their first choice, they go there as their last choice, having been ignored or rebuffed in every other forum.

"States can obviously challenge it [but] it is more likely to be an affected water user and it may be an environmental group."

Professor Williams believed the likelihood of such a move depended on how far politicians were prepared to go to fix the river system.

"Either the plan starts to operate in a way that makes the river sustainable and a healthier river, otherwise people will start to walk away from it, it has no credibility with the users," he said.

Commissioner Bret Walker SC said basin officials committed gross maladministration. ( ABC News: Isabel Dayman )

What do the MDBA and other basin states say?

Yesterday, the MDBA hit back at claims it had acted illegally, but conceded more investigation was needed.

"The Murray-Darling Basin Authority acts legally … it behaves well, it's fully transparent," chief executive Phillip Glyde said.

Victoria's Water Minister Lisa Neville said up to 12 regional towns would not survive if more water was reserved for the environment, as recommended.

"I think at this point to change the goal posts, to move away from this, would be in my view disastrous," she told AM.

New South Wales Deputy Premier John Barilaro and Regional Water Minister Niall Blair released a statement that said the "the gloves are off".

"The NSW Government will fight tooth and nail for our rural and regional communities. They need certainty. They need to know they have a future in the towns they love, communities they work in and the places they raise their families," the statement said.

"What they don't need is hysteria, legal challenges or more politicking."

South Australian Water Minister David Speirs said he did not want to do anything to put the current plan at risk and said South Australia had "the most to lose" if the plan collapsed.

"And so, the Marshall Liberal Government will do everything we can to make sure that plan remains intact and it continues to deliver and delivers in a better way for the future for the environment, for our communities in a social sense, and also economically by sustaining a healthy working river into the future," he said.