Blue-green algae concerns prompt push for demolition of Mannus Lake Dam

Australia Broadcast Center

a day ago

Over a decade, Leigh McColl and his family would walk down to a nearby creek to cool off in the warmer months.
The family swims ended in 2017 after testing of the water showed it contained blue-green algae, a bacteria that causes blooms in bodies of warm and still water.
"Charlotte, my middle daughter, got extremely sick … we used to swim in [Mannus Creek] every night," Mr McColl said.
Charlotte's symptoms included fatigue, respiratory infections, "ice-pick" pain, joint pain and severe brain fog.
Mannus Creek runs through Mr McColl's property, south of Mannus Lake Dam at Tooma, in the New South Wales Riverina.
The farmer said he had not been able to use the creek water for agriculture due to the algae blooms.
"I've got business implications … we are in the second year of drought and we've got water that we can't use," Mr McColl said.
The dam in the NSW Snowy Mountains was built in the early 1980s by a local man for private fishing use.
It became property of the Snowy Valleys Council following the man's death and remains under council operation.
Mr McColl is part of a group of landholders calling for the dam to be destroyed and turned into a wetland.
A report to the council estimates the demolition cost would be $13 million.
Simon Mitrovic, professor of freshwater ecology at the University of Technology Sydney, said blue-green algae was becoming more prevalent across Australia, with summer the most common season for blooms.
"The surface of the water gets hotter than the bottom of the water, and those two layers actually separate," Dr Mitrovic said.
Mr McColl's mother-in-law, Yola Cox, moved to Tooma in 1977 and lived on a property surrounded by Mannus Creek.
"It was the most beautiful crystal-clear water and had every fish variety, and every platypus and every frog," she said.
"Since then, a lot has changed.
"We used to use it as drinking water. All my children grew up on the Mannus Creek water, and so did all of my animals."
The federal government's Water Quality Australia website states that exposure to blue-green algae can cause damage to the nervous system and liver, as well as irritation to the skin and eyes.
Mannus Lake Dam is no longer a source of drinking water, but Dr Mitrovic said the algae was "also a potential risk for people using water recreationally" and some animals.
Dr Mitrovic was contracted by the Snowy Valleys Council in 2018 to conduct a study into the dam's blue-green algae.
He recommended a mixer be placed in the dam in 2019 to help circulate the water, however, a follow-up report in 2022 found the effectiveness was minimal.
Dr Mitrovic said his team had to wait until "a low inflow period" to test the efficacy of the mixer.
"At that time, it did coincide with more algae blooms," he said.
His most recent report, which indicated it would cost up to $13 million to deconstruct the dam, was discussed by the council last month.
Councillors voted to further investigate the feasibility of a wetland.
The Downstream Users Group advocates for demolishing the dam, which was under green alert last month for blue-green algae at low water densities.
The algae blooms have been present at Mannus Lake Dam for about seven years.
Spokesperson John Williams, who is Ms Cox's partner, said turning the dam into a wetland would "soak up" the algae.
"The flow will be running the whole time," he said.
"There will still be swimming, fishing, everything will be here, and it would be a lot better area."
Fellow Tooma resident and Downstream Users Group member Roger Paton said it had been a long campaign calling for the destruction of the dam.
"Whatever we send downstream goes to South Australia, so pretty much everyone will feel the consequences of it."
Mr McColl believes his daughter's illness was the result of exposure to the blue-green algae.
The family received inconclusive results after several medical appointments.
After exhausting all options, they contacted a naturopath in Western Australia in 2024, who found Charlotte had Chronic Inflammatory Response Syndrome (CIRS).
CIRS is a multi-symptom illness caused by inhaling biotoxins, which include mould and blue-green algae.
The disease is not formally recognised in Australia, however, its biomarkers are the subject of a Macquarie University study in relation to mould and dampness.