593 GATES IN THE WAY
Twenty thousand square kilometres of South Australian coast turned toxic, more than 550 marine species died and the peer-reviewed report into what caused it lists nutrient-rich water coming down the River Murray as one of the three main ingredients.
That investigation was led by SARDI and reviewed by scientists in Tasmania and the United States, so nobody gets to wave it away. It found the bloom needed three things happening at once, the nutrients carried down in the 2022-23 flood, a record coastal upwelling in 2023-24 and a marine heatwave sitting about two and a half degrees above average from September 2024.
What the report does not go near is what those nutrients have to get past on the way out.
The Murray-Darling Basin Authority describes its own barrages as 593 gates and stoplog bays across five structures, making a barrier 7.6 kilometres long that isolates the estuarine area from the Lower Lakes and holds those lakes about 0.75 metres above natural sea level. Their words not mine. That has been the arrangement since 1940. A working estuary dilutes nutrients, processes them and flushes them out to sea, while a system pinned at an artificial level behind 593 gates does none of that, which is part of why the Murray Mouth now needs dredges running to stay open at all.
So the science traced what came down the river and what happened out in the ocean, then stopped at the barrier sitting between the two.
There is already a plan for this and it has been with the government since 2023. Ken Jury, a Goolwa journalist who has spent years working on the lower Murray, put it to the Basin Plan Implementation Review as Submission 100. It keeps the barrages rather than tearing them out. It adds one new lock above Wellington so the pool up to Lock One can be controlled, upgrades the barrage gates so releases can be timed with an outgoing tide to properly scour the mouth, and clears Bird Island, a sandbank that grew after the barrages went in and now blocks around 70 per cent of the flow out of the Mundoo Barrage toward the sea.
Run it that way and the Lower Lakes go back to being an estuary, mixing ocean water with a controlled release of fresh. On Jury's numbers that frees up roughly 2,700 gigalitres a year of freshwater currently disappearing into evaporation and seepage across two shallow lakes, water that could stay upstream growing food.
His figures deserve proper testing rather than blind acceptance, and proper testing is exactly what has never happened, while another round of buybacks keeps getting treated as the only idea in the room.
South Australia has just lived through the worst marine disaster in its history while we are still arguing about how much more water to take off farming families in Deniliquin, Leeton and Griffith. Put Submission 100 on the table and model it honestly.
