Managing blue-green algae in Torrens Lake

Torrens Lake suffers from frequent and repeated blue-green algae (cyanobacteria) blooms – but we successfully help to manage them.

These microscopic blue-green algae – or cyanobacteria – are naturally occurring, but can reach high concentrations, known as a 'bloom', in situations where warm temperatures, stagnant water and high nutrient levels combine. The hotter and drier the summer is, the higher the risk.

In high concentrations, blue-green algae can discolour water, form scums, produce unpleasant odours, and release toxins that can be harmful to both humans and wildlife. As a result, once blue-green algae concentrations reach a particular level, Torrens Lake is temporarily closed to the public for health reasons.

These lake closures can extend over weeks and months, causing significant social, economic and environmental impacts. Thanks to our management program, this has been avoided since 2013.

The Torrens Lake suffers from frequent and repeated blue-green algae (cyanobacteria) blooms. These microscopic blue-green algae are naturally occurring, but can reach high concentrations (or 'bloom') in situations where warm temperatures, stagnant water and high nutrient levels combine.

What is being done?

An algae management program was developed with the support of Green Adelaide, the Department for Environment and Water, SA Water, the Environment Protection Authority, and the cities of Adelaide and Charles Sturt.

As part of the project, a variety of strategies have been tested to keep blue-green algae concentrations in the lake down over summer. The most successful strategy to date is to provide a managed flow of fresh water down the river. This flow dilutes nutrient levels, cools the lake water and keeps it well mixed.

The amount of water released depends on summer weather conditions at the time and the frequency and volume of recent rainfall. To help the water out to sea, a small channel is excavated across the beach from the Torrens outlet to the sea at West Beach.

Other initiatives that support reducing the frequency and intensity of blue-green algae blooms include:

  • Remote water quality monitoring at a permanent station in the lake throughout the year.
  • Twice weekly water quality monitoring at 7 locations in the lake over summer.
  • Annual fish monitoring along the river and around the lake.
  • Regular removal of pest fish species, European carp.
  • Woody weed removal and replanting along River Torrens Linear Park.
  • Gross pollutant traps on the lake and creeks that feed into it that captures thousands of tonnes of rubbish each year.

More information

For further information about the project, check out these resources:

FAQs

Blue-green algae FAQs