University of Canberra water ecologist Ross Thompson is hoping there's a simple explanation for Lake Tuggeranong's constant toxic blue-green algae outbreaks.
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"It wouldn't be impossible that when the suburb was built there was a cross-plumbing issue; a sewer has been plumbed into a storm water drain," Mr Thompson says.
But Mr Thompson isn't holding his breath as he works to determine how to rid Lake Tuggeranong of the nutrients that fuel the constant outbreaks.
While it's always been known Lake Tuggeranong has an excess nutrient problem, it's never been determined how.
For Mr Thompson, the first step was to figure out the extent to which nutrients were stored in sediment in the lake.
"A lot was the answer to that question," Mr Thompson said.
He then needed to determine the amount of nutrients coming into the lake.
"It was just so much more than anything we expected," he said.
"We went back to the ACT government and said 'It's not about whether you've got nutrients in the lake or nutrients in the catchment - you've got both'."
The water ecologist set up a series of what he called "big plastic bags", which create miniature versions of Lake Tuggeranong in five separate 160,000-litre columns, with a total volume equal to a third of an Olympic-sized swimming pool.
They allowed Mr Thompson to test different products and ways of treating Lake Tuggeranong on a small scale, before the government spent millions treating the entire lake.
"Some of those products could cost five or six million dollars, and it might have to be treated every two to five years," he said.
But when asked why he wanted to try to save a lake with what he called a deserved reputation for being near unswimmable, he pointed to his young son Zac, playing with another child by the lake's water.
"These guys," he said.
"It's nice in a hot landscape on 40-plus degree days to come down to the lake."
He said he hoped his son could more frequently enjoy Lake Tuggeranong, like Canberrans could already enjoy Lake Ginninderra and Lake Burley Griffin.
In the 10 years to 2017, the lake was closed for an average of 93 days each year due to blue-green algae outbreaks.
But even if Mr Thompson and his colleagues manage to determine the best way to treat Lake Tuggeranong, it will still need a decade of treatment before it becomes swimmable.
Another experiment Mr Thompson is running is determining whether a lack of light penetrating the lake makes it forever untreatable.
"You can try and improve the clarity of the lake but it's pretty tough to do," he said.
Then there is the invasive carp in the lake which keep stirring up the nutrient-rich sediment, exacerbating the algae outbreaks.
To make things worse, Mr Thompson said he'd even caught fisherman introducing baby carp to the lake by the bucket load.
"It's a real pain because you'll clear them out and they'll move them back in," he said.
"They're a horrible fish. There's little to like about the carp. They're not even good eating."