18 November 2022

Thoughtful planning can reduce the risk of toxic algal blooms in Lake Ginninderra

| Katrina Condie
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algal bloom in lake

There are fears that Lake Ginninderra could experience a toxic algal bloom of the magnitude seen in Lake Tuggeranong in 2019. Photo: Alica Tschierschke.

Scientists fear a decline in water quality could increase the likelihood of significant toxic blue-green algal blooms in Lake Ginninderra.

University of Canberra Professor of Water Science Dr Fiona Dyer says ongoing development and a sharp population increase in the Gungahlin and Belconnen areas could lead to a rise in algae levels in the lake, making it unsafe for swimming.

She says there has been an increasing incidence of toxic algal blooms over the past 10 years in Tuggeranong, Ginninderra and Lake Burley Griffin.

“For me, Ginninderra’s the worry because it has previously had the best water quality of all the lakes,” Dr Dyer said.

“Everybody has had their eyes on Lake Tuggeranong and Lake Burley Griffin, but haven’t really kept an eye on what’s going on in Ginninderra.

“With the increasing development through that catchment, including up north into Gungahlin, there’s increased pressure on Ginninderra’s water quality.

“I would hate to see it go the way of the other two lakes.”

The warning signs are obvious, with more instances of high concentrations of blue-green algae recorded in Lake Ginninderra over the past five years than in the previous five years.

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To reduce the risk, Dr Dyer says, urgent changes are needed to the way new suburbs are planned, to ensure more environmentally sensitive development occurs in Canberra’s lake catchments.

“We’ve got to stop nutrients getting into our waterways and flowing into our lakes,” she said.

“We need greater focus on water-sensitive urban design standards and need to be very mindful of how we implement them. Our planning approaches need to change now, rather than waiting until we have a huge problem.”

High concentrations of nutrients such as nitrogen and phosphorus cause algal blooms. These nutrients can come from things such as built-up leaf litter and fertilisers.

Dr Dyer says Canberrans need to do things that prevent sediment and nutrients from making their way into creeks and drains that flow into the lake.

“This means slowing the flow of water, making sure we have good ground cover and keeping our road gutters clean,” she added.

Dr Fiona Dyer

Dr Fiona Dyer collects a water sample from a stormwater drain that flows into Lyneham Pond. Photo: Supplied.

Continuing to incorporate things such as wetlands and rain gardens into urban planning will keep rainwater in the ground and reduce run-off during big rain events.

“We need to work hard to slow the runoff from rainfall, allowing rain to infiltrate into the soil profile,” Dr Dyer said.

“We need more gardens rather than concrete in our urban areas and, really, we need to be limiting people’s capacity to live right on the edges of our lakes until we get this under control.”

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Every Canberran can play a part in keeping their neighbourhood lake clean by sweeping up leaves and not letting them “stew” in the gutters, and reducing the use of fertilisers on their property.

Dr Dyer’s team at the University of Canberra carried out technical analyses of the lakes as part of the State of the Lakes and Waterways in the ACT report released by the Office of the Commissioner for Sustainability and the Environment in August.

She says the report revealed the state of the lakes and identified future risks to the health of the waterways and nearby residents.

“The report highlighted the increasing incidence of blue-green algal blooms as we increase Canberra’s population, and also highlighted the potential risks to people’s health into the future.”

cyclist at lake

A Canberra scientist is calling for tougher restrictions on developments around Canberra’s lakes, including Lake Burley Griffin. Photo: Michelle Kroll.

Research indicates that neurotoxins produced by blue-green algae pose significant risks to human and animal health. And there are increasing concerns about the links between neurodegenerative disorders and prolonged exposure to those toxins, such as motor neurone disease.

“These things won’t affect you in the next couple of years, but someone who lives beside a lake that has a blue-green algae bloom every summer could experience these problems down the track,” Dr Dyer said.

“You wouldn’t want to risk your kids developing these problems.”

She says the ACT Government is “doing what it can” to address “quite a substantial risk to society”, but explained there needs to be careful thought put into development around lakes.

“People need to take this issue seriously and play their part,” she said.

Canberra residents can check the state of their lake here.

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Difficult problem:
1. High high-density development equals smaller garden areas to absorb water; hence increased run-off.
2. Increasing our canopy cover by planting more trees equals more leaves in gutters and the stormwater drains.

If the Government didn’t insist on planting (and preserving existing) gum trees, just maybe the situation wouldn’t be so bad?
Deciduous trees get a bad rap for their annual leaf dump, however, after a few weeks, it’s over and the cleanup is quick. Deciduous trees also
allow sunshine and warmth into our homes during winter.

Gums lose leaves throughout the year and are more likely not be cleaned up.
I expect that I’m no different to the vast majority of people. I only climb up on my roof and clean my gutters out when there is a storm predicted. I never sweep up the leaves from the roadside gum trees. (I’d be sweeping them up every day).
Then, come winter, with no natural light and warmth in my house, you guessed it, I’m cranking up the heater.

Capital Retro1:18 pm 21 Nov 22

Correct.

Replacing natural vegetation with urban development in river catchment areas is one of the reasons we are copping more floods.

Dr Dyer says the ACT Government is “doing all it can”, and “people need to…play their part”. I draw her attention to the plethora of high rises in the bottom photo of the article. Designed by developers, approved by the ACT Government. Not much room for people’s gardens.

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