Millions of fish have died in the Darling River near his town, Menindee, in outback New South Wales, Australia in March 2023. After days under the sun, their bodies had started to “break up…transforming the river that locals rely on for drinking and showering into an ecological wasteland. Authorities have said the mass death was caused by a lack of oxygen in the water, called hypoxia, a result of recent floods and a heat wave. But furious locals say the true root of the problem is the overuse of Australia’s biggest and most vital river system.

The disaster is the latest episode in a long-running battle over the Murray Darling Basin, a vast network of lakes and rivers stretching across four states in eastern Australia, which sustains much of the country’s agriculture and dozens of communities along its banks. In an arid country where social, economic and environmental interests clash whenever water runs scarce, the issue has pitted states against each other, and riverside communities against farms upstream.

The 2019 fish deaths happened during a drought and the 2023 fish deaths happened after a flood, said Richard Kingsford, the director of the Center for Ecosystem Science at the University of New South Wales. But, he said, the long-term causes were the same both times: “There’s not enough water in the river, and the whole system is engineered so that escape routes are closed.” Over-extraction means parts of the river run dry more often, he said, and the small and medium-sized floods that used to periodically clear away organic debris have all but disappeared. That means when a big flood hits, that debris is all swept into the river, where it breaks down and deoxygenates the water. That, combined with the construction of weirs that have prevented the fish from swimming to better-oxygenated water, has made this disaster worse, he said….

The New South Wales fisheries and water management bodies, by contrast, both attribute the disaster to weather-related causes…

After many of the fish had already sunk to the bottom of the river, the cleanup started with workers in small boats removing floating carcasses with hand-held nets. Authorities said this will be followed by machinery that will drag nets through the river to scoop up sunken fish….

Excerpts from Yan Zhuang, A River Choking on Fish Corpses, and a Community Full of Anger, NYT, Mar. 24, 2023