A million dead fish, floating on putrid green water. Images of this ecological catastrophe on the Darling River over summer shocked the nation. Was it the result of drought? Blue-green algae poisoning? Excessive summer temperatures and climate change? Too much water taken upstream for irrigation? Mismanagement by the authorities?
After several months and at least four published reports, we know the answers. It’s time to state plainly what has been going on, and who is to blame.
For the immediate crisis of the fish deaths, we can look at the Interim Report to the Australian Government, released 20 February. There were three large-scale fish kills, all in the Menindee region of the Darling River. This is the point in south-west New South Wales where the river reaches the Menindee Lakes. It’s hot and dry, averaging about 250mm of rain a year.
During two periods in 2012 and 2016, it rained enough to fill the lakes. When full, these lakes become important nurseries for native fish. If a lot of water is flowing through the river, the fish can travel both upstream and downstream. Flowing water also circulates oxygen within the water column and helps to reduce algal blooms.
After 2016, there were no further inflows of water to the lakes. Some water was released downstream for the environment, but the largest flows (peaking at 6200 megalitres a day) were for the River Murray, to meet commitments at the South Australian border and for the irrigation season. To get there, the water passed over a nearby pool called ‘Weir 32’, which is much smaller than the lake. Fish and algae went with the flow, but as the water level dropped they became trapped in the weir pool.
The dry conditions continued. Rainfall for the northern Basin in 2018 was about half the long-term average. Most of the Murray-Darling had its hottest December-January period on record. The highest temperature in Menindee was 48.8 degrees, three days before the third mass fish death.
When it gets this hot and the river isn’t flowing much, the water column splits. There’s a layer of hotter water at the top, and cooler water at the bottom. The temperature difference means the layers can’t mix. This keeps most of the oxygen in the shallow and warmer surface, while the much larger and deeper bottom layer becomes deprived of oxygen. The fish would have been pushed into the shallow surface waters, which were also covered in algal blooms.
Then the cool change arrived, and the water temperature plummeted. Winds stirred the waters, mixing the two layers. Suddenly the amount of oxygen in the shallow surface layer wasn’t enough for the total volume, and the die-off of algae also sucked up more oxygen. The fish had nothing to breathe and nowhere to escape. They suffocated in their millions.
That’s the immediate reason for the deaths, but for the ultimate cause we have to look at a different report from the Australian Academy of Science. For all the technical explanations, it’s actually pretty simple. ‘The root cause of the fish kills is that there is not enough water in the Darling system to avoid catastrophic decline of condition through dry periods.’ And prevention is simple too. To reduce the risk of algal blooms and splitting of the water column, we need more water flowing down the river.
So why isn’t there enough water in the Darling? The answer is ‘excessive diversions upstream’. In other words, it’s big irrigators in NSW and Queensland taking too much water for their own purposes. One particular concern is unregulated ‘floodplain harvesting’. Agribusinesses have built channels, levees and huge storage dams to capture water flowing on the floodplains and use it to irrigate thirsty crops like cotton, but this isn’t properly monitored or reported.
However the biggest swindle isn’t irrigators taking advantage of loopholes, but how the whole system has been rigged in their favour — possibly illegally. This argument is set out in the South Australian Royal Commissioner’s scathing assessment of the Murray-Darling Basin Plan, released late January.
The whole point of Australia’s Water Act 2007 and the subsequent Murray-Darling Basin Plan, writes the commissioner, is to restore the degraded environment. In fact, the Commonwealth’s key legal justification for muscling in on the states’ business is our international treaty obligations on wetlands and biodiversity. The act requires setting an environmentally sustainable level of water that can be taken from the river, based on the best available science.
Instead, the Murray-Darling Basin Authority has consistently dismissed independent scientific recommendations and based its water targets on politics. The environment is supposed to be primary, but the MDBA has adopted a ‘triple bottom line’ approach that includes social and economic factors. And their target has failed to take into account the hotter and drier conditions expected under climate change.
The target of 3200 gigalitres of water to be recovered for the environment was a political compromise, and it’s been further compromised since. Myths and lies about the economic impact of returning more water to the river have spooked communities in the Basin. Bowing to this backlash, the government has capped ‘water buybacks’, which are the most efficient and socially just way of restoring our river to health. Instead, millions of dollars has been wasted on efforts to make irrigation more efficient, without evidence that the water saved will actually benefit the environment.
Even the water that has been recovered may not have flowed where it was intended. A study by the Wentworth Group of Concerned Scientists found that ‘there has actually been no improvement or even a decline in water flows since the implementation of the Basin Plan’. Dams and weirs are impeding the flow of water and it’s hard to ‘shepherd’ this water through the system. Most scandalous of all, under NSW water-sharing rules ‘water that should have been left in the rivers, for environmental purposes, can be extracted’ by irrigators.
The result? If a similar situation occurs that led to the recent fish kills, we won’t have enough water flow to do much about it. The best we can do is localised techno-fixes like using mechanical aerators to increase oxygen levels in the water.
Even less encouraging is that key solutions to deliver more water involve repealing recent compromises of the Basin Plan, such as the cap on buybacks. That’s the right thing to do for the environment, but it could just lead to another cycle of fighting. It’s starting to look a lot like the politics of climate change, with back-and-forth policy that achieves very little.
When you think about it, the future is downstream of the present: our children will inherit the consequences of any decisions we make today. In this sense we all live downstream, and we need to take the long-term view when considering the Murray-Darling Basin.
I believe we should implement the recommendations of the South Australian Royal Commission — even at the risk of starting another fight between the Basin states — because it’s better than the current trajectory: the long, slow death of our greatest river system.