Algal blooms and lake closures

Our lakes have a dual purpose. Designed not only for recreation and to provide a beautiful focal point, they also play an important role in cleaning stormwater.

Big concrete stormwater drains built in the 1960s and 1970s were designed to rapidly move rainwater away from our homes and streets and into our lakes. The lakes trap the pollutants carried by the stormwater and run-off and prevent them travelling into the Murrumbidgee River.

They do a good job, particularly during major rain events when large amounts of pollutants, nutrients and sediment are washed into the stormwater system.  However, over time and particularly after heavy rain, the build-up affects water quality and lakes may be closed.

The most common reason for lake closures in the ACT is blue-green algal blooms. There are actually three types of blue-green algae, generally occurring at different times of the year. They are all toxic to dogs when ingested and potentially hazardous to humans, causing symptoms such as eye or skin irritations, sore throats or gastro-enteritis. Lakes are closed when algal levels are high enough to be considered a risk.

We’re still working to understand exactly why and how algae grow but we know they feed on nutrients caused by pollution, including excess fertilisers, sediment run-off, leaves and grass clippings that arrive in our waterways via the stormwater system.

Get more information about blue-green algae, monitoring, lake closures and alerts on the TCCS website.