Managing a river is all about day-to-day decisions for long-term benefit, and this year we have been fortunate to have had the advice and perspective of people in the Murray region to help us grapple with challenges in a very important part of the river.
In the spotlight has been the sand that has steadily filled the deep pools, covered up snags and continues to reduce the volume of water getting through the Barmah–Millewa reach – known as the Narrows or the Choke.
We have spent a good part of the year on the first stage of this investigation, which has revealed that the sediment accumulating on the riverbed is building up no matter what the flow of water. In other words, it is not being flushed out the other end.
Looking forward, we expect the sand will further damage the river ecology through the two RAMSAR listed national parks. It will impact on cultural sites, reduce access to recreational areas, reduce the water that can pass through without breaking the banks, and it will increase the risk of a delivery shortfall for downstream water users.
A key concern is that, as the bed of the river fills with sand, the river responds by trying to get wider. We see this in the accelerated bank erosion and subsequent breakout of water into the forest. Breakouts can result in the forest receiving water at times when it would otherwise be dry, which harms the natural ecology. This unseasonal watering also means an increased loss of this precious resource from the River Murray System.
Doing nothing is not an option – it would be inconsistent with the values that the community has identified for this amazing reach of river.
So how to tackle the way forward? This century-old problem clearly can't be reversed overnight, and it needs a multi-pronged approach.
Last month, Basin governments agreed to our plan to explore a range of possibilities to manage the sand. These include potential targeted removal of sand, works to manage water that escapes from the river through the Barmah–Millewa Forest, and use of irrigation infrastructure to transfer water around the reach at peak water delivery times.
In the short term, the MDBA is partnering with New South Wales and Victoria to prevent and manage unseasonal watering while we develop options for sediment removal.
Removing large amounts of sand from such an important environment poses a significant challenge. We will need to consider how to remove the sand from the riverbed, where will it be moved to, and whether it has commercial value. And can we do this in an environmentally, culturally and socially acceptable way?
The suggestion of moving water around the forest over the summer and autumn is being scrutinised under the Barmah–Millewa Feasibility Study, which is scheduled to report to the Ministerial Council in December 2022. These investigations will be done in partnership with state agencies and private irrigation operators.
Apart from drawing on technical expertise, the success of meeting this challenge will hinge on continued discussion and advice from First Nations, irrigators, communities, local government, state water authorities, National Parks representatives and environmental agencies. This way you will know what we are considering, and we can learn from local experience and knowledge to help shape viable solutions.
We've spent considerable time this year talking, and these conversations won't stop. We know the local community, like us, are committed to preserving this magnificent stretch of river.
The report into the first stage of the investigation is available to view now at the MDBA website: Barmah–Millewa reach sediment investigations.
Find out more about The Barmah Choke.
Dr Ben Dyer
ENDS
