Manly Dam is one of the Northern Beaches best kept secrets offering a gorgeous bushland setting for picnics, swimming and bird watching.

Council actively manages Manly Dam and run weekly tests to monitor water quality. This is done by both field and lab testing to ensure we have a regular, up to date picture of how the water quality is tracking.

The tests primarily check for blue-green algal blooms which can pose a risk to human health. We have measures in place to minimise blooms and there is a large propeller near the dam wall which disperses the bacteria before it blooms.

Any sign of a bloom triggers Council to warn visitors and strongly advise against swimming.

The last significant blue-green algal bloom was almost thirty years ago and the Dam consistently remains open to recreational users.

Blue green-algae is a naturally occurring bacteria found in freshwater environments and bloom under certain natural conditions. For more info on the science of blue-green algae check out the CSIRO website.