What killed a million Darling River fish?

Reports that around one million fish have died along the Darling River in New South Wales have caused a stir this week, among conflicting reports about the roots of the problem.

This is the second incident in a few months – the first occurred upstream just before Christmas last year, resulting in the death of 10,000 fish along a 40km stretch of the Darling River.

Water NSW and the NSW Department of Primary Industry initially blamed ongoing drought conditions, which they say resulted in algal blooms consuming so much oxygen that fish could no longer survive, and reducing water quality.

Locals and the media have said the real problem lies in water mismanagement and, in an Expert Reaction to the AusSMC, Professor John Williams from the Crawford School of Public Policy at ANU said he too wasn’t convinced the drought is to blame.

“Dead fish and dying rivers are not because of the drought, it’s because we are extracting too much water from our rivers,” he said.

“Many of the large fish which are dying have lived for more than 50 years through many equally severe droughts. Drought is part of the system and any plan must be able to manage our rivers through drought whilst maintaining ecological resilience of the rivers and floodplains.”

Unusual situation

Associate Professor Simon Mitrovic, from the University of Technology Sydney told the AusSMC that algal blooms are actually fairly common in the river during summer. But “it is unusual to get a fish kill occurring at the same time”, he said.

And while it is an unusual situation, experts told the Centre that this kind of devastation has happened before.

“We have been here before with the algal bloom of 1991 along the Darling River and the ‘blame game’. Water reform and the Basin plan was supposed to fix this, but it hasn’t,” said ANU’s Professor Quentin Grafton, UNESCO’s Chair in Water Economics and Transboundary Water Governance.

“The problem is that we are extracting too much water from the river and not leaving enough for the fish or anyone else who actually wants to swim or enjoy our river systems,” he added.

“Sadly unsurprising”

Professor John Quiggin from the University of Queensland described the disaster as “sadly unsurprising”.

“The Murray Darling Declaration, released by leading water experts in 2018, pointed out how political decisions driven by ignorance and expediency have compromised the environmental goals of the 2007 Water Act, and led to massive waste of public funds on projects of little or no benefit,” he said.

Prof Quiggin said the 2007 Water Act outlined required measures that still haven’t been put into place, such as an “independent, scientifically-based entity to publicly document what is happening in the basin”.

Professor Jennifer McKay from UniSA went one step further, saying: “we need the Water Act to be applied to the entire nation. There is no reason in law why it could not.”

Limitations to irrigation needed

To reduce the risk of another mass fish death, Professor Mike Young from the CRC for Future Fuels said Australia should set flow requirements and limit irrigation to areas where water offtake is metered.

And Prof Williams told the AusSMC that he believes those responsible for the mismanagement of the Darling should be held to account.

“The vision of returning the Basin Rivers to healthy, sustainable, working rivers has been lost. We must find it again and place it on centre stage,” he said.

“It’s a national shame and international embarrassment how we are currently managing our iconic and much-loved river system. Australians can do better than this.”

Read more comments from Australian experts here

This article was first published on Australia’s Science Channel, the original news platform of The Royal Institution of Australia.