RICHARD KINGSFORD. The catastrophic fish kill on the Darling River– decades in the making

Jan 16, 2019

The plight of the Darling River shocked the nation last week, when up to a million fish were killed by lack of oxygen, accompanying the disruption of a blue-green algal bloom on a forty kilometre stretch of the river near Menindee, southeast of Broken Hill. This followed a similar kill of tens of thousands of native fish in December.

The ongoing coverage on social and mainstream media has been dominated by widespread finger pointing, principally about whether this was a natural event caused by the drought or mismanagement of the river.

This catastrophe is about what’s happened the length of the river over the last three years and last thirty years. The fish kill is tied to mismanagement of the river, exacerbated by the drought, but avoidable in the future if we learn from our mistakes. Blue-green algae, naturally in our rivers, usually start ‘blooming’ when rivers stop flowing and temperatures climb above about 20oC.

Blooms have inexorably extended their grip along the length of the Darling River, turning it green, as temperatures have increased over the last few months. But after searing forty degrees temperatures in the first week in January, air temperatures at Menindee dropped to 16 oC on 6 January.

As a result, authorities believe two factors sucked the oxygen out of the river: mobilisation of oxygen depleted water from the bottom and the death of blue-green algae. With little oxygen exchange over their gills, there was this unprecedented fish kill, a magnitude never experienced previously in the Murray-Darling. The proximate causes were clear, but the questions everyone is asking could we have avoided it and what of the future?

A video from Tolarno Station went viral, as a local farmer and his friend passionately pointed the finger at government mismanagement, while holding a large dead Murray cod, probably at least two to three decades old. They had survived similar previous droughts, including the Millennium Drought (peaking in the 2000s), the next worst drought after the Federation drought of the late 1800s.

However, NSW Minister for Department of Primary Industry and Water and Federal Minister for Water, David Littleproud and Cotton Australia pointed their fingers at the drought. Most of the irrigation water from the Darling River catchments is used to grow cotton. These protestations ignore the evidence that this once mighty river is now only a shadow of its former self. Over the long term, nearly half of the average annual river flow (44-47%) at Menindee is taken out upstream, mainly for irrigation. The Darling River is now experiencing ‘river droughts’ much more severe and prolonged than ‘droughts’ measured in rainfall. The river stops flowing more often and for longer than it used to. This drives more blue-green algal blooms and other river degradation.

A moderate 2016 flood in the Darling, which filled Menindee Lakes, is now just a distant memory. The lakes filled to above 640 GL (around a third of their total capacity) and this water was progressively managed by the Murray-Darling Basin Authority, under an agreement with all the states, to supply downstream irrigation, towns and the environment of the lower Murray. The New South Wales Government then took over management responsibility when lakes fell to just above a quarter full (480 GL). In water, everyone is managing.

There are questions about where all the 2016 water went to and why wasn’t some kept back to deal with potential blue-green algal problems – and save the fish.

More importantly, there are questions about the current and future strategy of managing the flows in the whole river and its tributaries. Despite the Murray-Darling Basin Plan, water management still largely remains a ‘business as usual’ approach, with lip-service paid to environmental issues while engineering the system into more efficient delivery of irrigation water. A government water engineer once remarked that Murray-Darling rivers are like F1 racing cars, you need to keep fine tuning them to get the most out of them. The culture, governance and policy of water management is pre-dominantly about saving water for productive uses and not ‘wasting’ it in wetlands or rivers where it might evaporate.

Last year, the Australian Government, supported by the Labor Party in the Senate, decided not to grant the Darling River an additional 70 GL a year of flow under the Murray-Darling Basin Plan, on the recommendation of the Murray-Darling Basin Authority. This water would certainly have helped avoid similar future catastrophes.

Instead, the political argument of cost to the irrigation industry prevailed, despite many experts arguing that ecosystem services such as native fish populations, water for Broken Hill and communities along the river would be the causalities. The old argument that water recovery was killing Basin towns reared its head, despite the plethora of other factors, including ageing populations and mechanisation.

What will be the environmental cost of this disaster?

The science is unequivocal – in the long run substantial reductions in water are neither good for fish, nor for other river plants or animals. There is little, apart from widespread flooding in the Darling River catchment, which will alleviate the current crisis, with experts predicting more kills to come this summer. Re-stocking the river, as suggested by NSW Primary Industry Minister Blair, is a nonsense – without water these stocked fish won’t survive, and they often don’t do nearly as well as wild bred fish anyway.

Buying back at least 70 GL a year of flow for the river from willing irrigators upstream is essential. Protecting flows down the length of the river is mandatory.

Taxpayers are paying for environmental destruction in the misapprehension that it is good for the river. It’s a nonsense. The $150 million Menindee Lakes efficiency project should be ditched, as it will make life for Murray cod and Golden perch even worse, destroying large expanses of their feeding, breeding and nursery habitat.

Until governments adequately heed environmental advice that is built on solid scientific evidence, then we will continue to see ongoing environmental disasters for the Darling and other rivers. Otherwise, decisions made by politicians for one small sectional interest will be to the enduring detriment of our rivers, the many who currently depend, enjoy and live on them, and future generations will be denied the benefit of these extraordinary inland water systems.

Richard Kingsford is the Director of the Centre for Ecosystem Science and Professor of Environmental Science at the University of NSW, Sydney

Share and Enjoy !

Subscribe to John Menadue's Newsletter
Subscribe to John Menadue's Newsletter


Thank you for subscribing!