Floods and frustration: the fish kill crisis in Menindee

In March 2023, a major ecological crisis near Broken Hill in outback New South Wales (NSW) hit the national headlines.

It was days before the United Nations Water Conference, the first in 46 years. Shocking news media stories and video showed a ruptured Darling-Baaka River blanketed by dead fish, its waters putrid with decomposing carcasses and town hall meetings thick with an atmosphere of anger and dejection.

So shocking was the extent of this mass fish kill that the newly sworn-in Premier of NSW, Chris Minns, flew to the small town of Menindee along with NSW Minister for Environment Penny Sharpe to witness the aftermath of the fish kill and speak to locals on the ground.

The Menindee Lakes community has seen this type of carnage before. It was only four years ago that massive fish kills in this same area of far west NSW attracted global attention. Now it has happened again.

A system of natural lakes fed by flows down the Darling-Baaka River, the Menindee Lakes are home to the Barkindji people. Called Wontanella in Barkindji language, meaning “many waters”, the lakes are an important nursery for golden perch and attract more than 200 species of birds, rivalling Kakadu for avian diversity.

Back in 2018 and 2019 the Darling-Baaka River, the third longest river in Australia, suffered one of the longest dry periods in recorded history and was reduced to a chain of stagnant green pools of water that were disconnected by the sun-baked sand of the riverbed.

More than a million fish suffocated in the dwindling weir pool at Menindee, causing an uproar about the effects of extraction for irrigation in catchments upstream of the Darling-Baaka River.

Two independent panels were commissioned to investigate the 2018-2019 fish kill. Both reports found that upstream irrigation and climate change had exacerbated a climactic drought. Water sharing arrangements led to the extraction of small and medium water flows that would have otherwise kept the pools of water in the Darling-Baaka River until the drought broke.

Since the 2018-2019 fish kills, the Murray-Darling Basin has had three years of very high rainfall and enormous floods, which have brought much-needed relief to the floodplains, lakes, billabongs, creeks and backwaters, creating an abundance of life and giving Menindee Lakes a chance to be restored to their former glory.

But after floodwaters had receded from Menindee, fish started to die, eclipsing the previous fish kill, with numbers upwards of 10 million.

The affected fish are mostly bony bream — a small-bodied native species that is a critical part of the food chain for other wildlife.

It’s not uncommon to see fish die after a flood, especially bony bream, which are susceptible to low oxygen water. This is because during and after a flood, as water recedes from floodplains it brings with it leaf litter, twigs, dirt, bacteria, insects and other organic matter that provide valuable nutrient and food for fish and other aquatic life. Too much of this nutrient can create a bacterial reaction, which strips oxygen from the water and suffocates fish. This is referred to as hypoxic blackwater.

While death events from blackwater have been known to occur, no one in Menindee had ever seen this level of decimation before. Locals wanted answers.

An inter-agency operation coordinated by NSW Police was set up three days after fish began dying in droves. But agency representatives from various water authorities deflected community concerns about how upstream irrigation had impacted the health of the river, instead trying to limit the conversation to the safety of the drinking water and the pending clean-up.

According to some community members and experts, the recent fish kills are a result of poor flood management and operational decisions around managing the accumulation of hypoxic blackwater. There have been criticisms about the lack of preventative measures, as well as the agencies’ slow response times, despite community members reporting deaths well before dead fish turned up in their millions.

At the community meetings held in the days after the March 2023 Menindee fish kills began, residents raised concerns about contaminants from upstream affecting water quality and the long-held concerns that water extractions, which reduce the frequency of floods, have altered the flooding regime and left the ecosystem vulnerable. 

For decades, river communities along the Darling-Baaka River have been actively trying to reverse the ongoing degradation of the river’s ecological health and urged to be included in the co-design of the solutions.

But trust between local stakeholders, departmental staff and policymakers is at an all-time low, and despite investment in restoring the Murray-Darling Basin’s ecological health, water injustices continue to plague the Darling-Baaka community. This is especially damaging for the Barkindji people who have no rights to cultural water and have been marginalised by decision-making processes.

With climate change expected to produce longer and more frequent dry periods, as well as bigger wets, managing the rivers in the Murray-Darling Basin sustainably is crucial for Menindee.

Fortunately, there has been some good news.

On the banks of the Darling-Baaka, Premier Minns promised an independent inquiry into the most recent fish kill. The exasperated residents of Menindee are hopeful the findings may provide some answers and lead to actions that reverse the rapid decline of one of Australia’s mightiest rivers.