The MDBA, an independent statutory authority formed under the national Water Act to oversee the Basin Plan, was slammed in the report of Royal Commissioner Bret Walker, who accused the body of maladministration, negligence and failure to act on the best-available scientific knowledge in determining basin-wide limits on the volumes of water that can be taken for human use.

Walker found the authority “completely ignored climate change projections for the determination of the [environmentally sustainable level of take] and the setting of a Basin-wide [sustainable diversion limit] that reflects this”.

“That is unlawful. It ignores the best available scientific knowledge. As an administrative decision it is indefensible,” he wrote.

“Politics rather than science ultimately drove the setting of the Basin-wide SDL… it is an unlawful approach. It is maladministration.

“The unlawfulness of the determination underpins and pervades the implementation of the Basin Plan.”

Walker’s report found the Basin Plan unlawful in several respects, including the determination of how much water should be returned to the environment – and recommended urgently re-setting the agreed levels of water use under the plan.

But the MDBA today published its rebuttal, roundly rejecting the criticisms and arguing the royal commission’s “main recommendations… effectively propose abandoning the Basin Plan and starting again”.

“The MDBA considers this would be a reckless act – setting back progress towards a healthy and sustainable basin, and causing substantial uncertainty for basin communities,” the authority argued in a statement signed by its five current members, including acting chair Joanna Hewitt, after the tenure of former chair and Liberal MP Neil Andrew expired last month.

The MDBA insists the Basin Plan and subsequent amendments were lawful and “were prepared consistently with the Water Act, relying on the Government’s legal advice and stand as law”.

“The fact that the South Australian Royal Commission report puts forward a different legal opinion on some aspects is not conclusive,” the response states.

“It is simply a different opinion.”

The authority “rejected” Walker’s findings of maladministration – which it labelled “assertions” and “claims”, arguing the commissioner put forward “no specific evidence for such serious accusations”.

“The MDBA is a principled organisation that abides by the Australian Public Service Code of Conduct… we demand the highest standards of ethical behaviour from our staff and from authority board members,” its statement said.

“Contrary to claims in the commission report, the MDBA is committed to using best available science and in conducting our work transparently.”

Walker’s report highlighted as “dangerous” the MDBA’s (and to a “lesser but alarming extent” the CSIRO’s), “habitual” and “unfathomable predilection for secrecy”, which he called “the bane of good science”.

The MDBA conceded that “as with any science-based organisation we can always do more to improve our work and our transparency… and we are committed to taking on the challenge”.

“We are already working with CSIRO to enhance our capacity to analyse how climate change will affect the hydrology and ecology of the basin,” it said, acknowledging that the draft business cases for supply measures “should have been shared with the community”.

But, it insists, it is the “basin states [that] are the proponents for these projects and responsible for the release of such information”.

“The MDBA reminded states at several junctures of the importance of transparency in this work,” the response said.

The response did highlight several “areas of agreement” with Walker’s report, including “strengthening our understanding of climate change and its likely effect on the basin’s water resources” and “improving the protection of environmental flows”.

Walker savaged the SA Government – and Environment Minister David Speirs – for agreeing to revised criteria that would make it easier for upstream irrigators to veto water-saving efficiency measures.

The MDBA said it agreed that “implementing the Sustainable Diversion Limit adjustment mechanism in the southern basin poses real challenges”.

“We are also concerned that progress towards recovering the additional 450GL through efficiency measures has been slow, and more work is needed to protect environmental flows,” it noted.

“For our part, we believe it is in the best interests of the basin, its environment, communities and industries to stay the course.”

The authority said the commission’s damning findings about its governance “overshadow other useful analysis and insights in the commissioner’s report that could improve future Basin Plan implementation”.

“The Basin Plan is starting to deliver,” it insisted.

“Once fully implemented, it will reduce water extractions across the Basin by around 20 per cent or equivalent and improve water use efficiency.”

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