Victoria has at last signed up. We can now look to one federal authority to manage the unfolding environmental disaster in the Murray-Darling Basin. While this development is truly historic, delivery of a healthier river system and reliable water supplies inevitably depends on detail.

Any watchers of river management over time know that the fate of our rivers has always resided in the hands of the “tap-turners” – the water agencies. These are the people who implement and interpret policy, make the annual allocation announcements, and manage access to the different types of floodwaters. A lot of detail resides in state water sharing plans, but there is still considerable “interpretation” required.

The MOU from COAG trumpets a “sustainable cap” for groundwater and surface water extractions but what of the Murray-Darling Basin Cap in place since 1995, supposedly freezing diversions at 1993/94 levels of development? Soon after its announcement, there was policy creep. Queensland successfully argued that, unlike the southern states its opportunities to develop had not been realised and so caps on its tributaries should come much later. Now diversions in the Condamine-Balonne, one of these rivers, has increased to a point where modelling indicates a 75% reduction in median flows to the iconic, internationally-listed Narran Lakes. Is the new cap more sustainable than the old one?

The COAG MOU announced that “current state water shares” would be “preserved unless otherwise agreed by all signatories”. This apparently cements any developments post the Murray-Darling Basin Cap. What happened to restoration of healthier river systems and addressing over allocation? There is wide acknowledgement of over allocation, including a basin-wide study by CSIRO identifying that the story is worse in some rivers than their jurisdictional governments would have us believe. We must not forget the River Murray’s sister river the Darling – often left out of discussion but with burgeoning problems.

Then there is the elephant in the room for river policy – water that flows over the river banks. Such water has been free and available for diversion. Networks of banks and channels crisscross our major regulated rivers, diverting this water from our floodplains. All such diversions need to be measured and audited. Such details will determine success or failure.

Unfortunately, this will all take time, time in which red gums continue to die, waterbird populations decline and our internationally listed wetlands plunge down the rankings table of conservation value.

Let’s not squander the opportunity and hope a strong river authority will emerge, independent of the major sectoral influences that have run our rivers. The new Murray-Darling Basin authority must have the expertise and resources to sort out the policy quagmire and attend transparently to the detail to ensure that collective vision is achieved.