The significance of water flow to the health of Australia’s rivers and streams was evident when as many as a million fish died in the lower Darling River in the summer of 2018-19.
There were multiple causes for the fish deaths that summer. In essence, a chain of events started with high water flows encouraging a surge in the fish population in preceding years. The extremely hot and dry summer that followed left these fish trapped in pools of water with weir barriers at one end and dry channels at the other. Climate conditions then contributed to depletion of the oxygen in the water, making the situation critical.
Research being led by Associate Professor in Freshwater Ecology Simon Mitrovic is reducing the likelihood of such events occurring in our waterways, and in particular the Murray-Darling Basin—Australia’s largest and most complex water system.
The Basin, which includes 23 major rivers and crosses four states and a territory, is particularly important because it supports what has been described as “the food bowl” of Australia. It is the subject of the Murray-Darling Basin Plan, a coordinated approach to water use across the various jurisdictions that aims to balance environmental, social and economic considerations.
Associate Professor Mitrovic, who leads the Freshwater and Estuarine Research Group in the School of Life Sciences at UTS, was among the panel of experts the Federal Government turned to for an independent assessment of the summer fish deaths in the Darling River.
The panel produced 24 findings on the causes and its report included 27 practical recommendations for policy makers and Murray-Darling Basin managers.
Associate Professor Mitrovic has spent more than 20 years researching water quality and algal blooms. His current research looks at the effects of environmental flow management—water released from dams or weirs, for example—on plant and animal life and the health of inland water systems.
His work has implications for land owners, water managers and irrigators, as well as the public as consumers of drinking water and recreational users of waterways. The Freshwater and Estuarine Research Group works closely with governments to solve environmental issues.
Among other things, Associate Professor Mitrovic has developed critical flow thresholds that can be used to reduce the chance of toxic algal blooms. These thresholds have been used in developing environmental flows to guard against blooms in the Murray-Darling Basin.
“Many of our projects are essential to determine if the environmental flows supplied in the legislative water sharing plans and Murray-Darling Basin Plan are having an environmental benefit,” he says.
There is a legislative requirement in NSW to review environmental water provisions in the water sharing plans every 10 years to ensure enough water is being allocated for a positive environmental benefit, he explains. Monitoring of the environmental water provided in the Murray-Darling Basin Plan is also required.
As well as contributing to the understanding of this particularly important water system, he says, “the work also adds to the understanding of many ecosystem processes that are poorly understood in Australian rivers generally”.
Read more about the report in the Darling River fish deaths on The Conversation.