Menindee Lakes fall to five-year low as experts warn of summer fish kills

Water levels at Menindee Lakes in western New South Wales have sunk to their lowest point in five years, leading the state government to restrict upstream water use. Experts say the decline raises the risk of mass fish deaths over the coming summer.

Combined storage across the lakes slipped below 480 gigalitres earlier this month, the first time that has happened since 2021. In the upper Menindee Lakes, volumes have fallen under 250GL, a threshold that activates temporary state water restrictions across parts of the northern Murray-Darling basin.

The restrictions curb access for some irrigators and are meant to protect water for critical human needs and the environment. They follow low rainfall in the catchment over the past 12 months. Experts say the danger of summer fish kills is growing unless flows down the Darling-Baaka River into the lakes improve.

Menindee has seen catastrophic fish kills before, in 2018, 2019 and 2023, when millions of dead fish washed up along stretches of the Darling-Baaka.

Prof Jamie Pittock of the Australian National University and the Wentworth Group of Concerned Scientists said officials are predicting with some certainty that deaths will occur without more water. "Government officials are predicting with a level of certainty that unless there's more water flowing into the Baaka-Darling River that there will be fish kills at Menindee this summer," he said. He called for a major rainfall event and for state governments to stop irrigators pumping out the first flush of water.

Graeme McCrabb, one of the first Menindee residents to raise the alarm over the 2018-19 disasters, said the lakes had reached "drought reserve volumes". He said that effectively means water must be conserved "at all costs". He noted that small inflows are now arriving across the Queensland border after recent rain there, which gives some hope, though more would be needed.

"If we don't get inflows, the risk [of fish kills] would be very high in January or February," McCrabb said. A milder summer would also reduce the risk, he added. "I'm worried about fish kills to be honest," he said, describing the sadness of seeing the water take on a green algal look.

Days after winning the 2023 state election, the premier, Chris Minns, and senior ministers visited Menindee and committed to investigating the mass fish kills. An expert panel was set up under the northern basin connectivity program. It recommended limiting upstream overextraction during dry periods to help sustain flows in tributaries feeding the Darling-Baaka River and Menindee Lakes, with the aim of reducing the risk of fish kills and large-scale drying.

The panel delivered its final report two years ago, but the state government has yet to implement it. McCrabb said he was disappointed the recommendations had not been followed. "Since the fish kills, government agencies have made no policy changes to improve water quality outcomes," he said.

Comment has been sought from the NSW water minister, Rose Jackson.