Blue-Green Algae Monitoring

Throughout the year the Environment Protection Authority (EPA) monitors the water quality at various sites in Lake Tuggeranong, Lake Ginninderra, and the Molonglo River. (Lake Burley Griffin is managed by the National Capital Authority. )

Blue-green algae grow naturally in Australian fresh and saline waters. They are usually found in low numbers. However, when environmental conditions are favourable their numbers increase rapidly creating a 'bloom'. Drought conditions, high summer temperatures and high nutrient levels are all important factors in creating the conditions to cause algal blooms.

Blue-green algae in very large numbers cause deterioration in water quality and pose a threat to public health. As blue-green algae die they can release toxins into the water. These toxins can cause symptoms such as eye or skin irritations, sore throats or gastro-enteritis in humans.

The ACT Guidelines for Recreational Water Quality (the guidelines), issued in October 2014, provide a framework for the managment of recreational activity in ACT lakes and rivers. The guidelines break down recreational use into two catagories, primary and secondary contact recreation.

Primary contact recreation: This involves whole-body contact in which the entire body or the face and trunk are frequently immersed or the face is frequently wet by spray, and where it is likely that some water will be swallowed, inhaled, or come into contact with ears, nasal passages, mucous membranes or cuts in the skin (e.g. swimming, diving, waterskiing, windsurfing).

Secondary contact recreation: This may involve incidental contact in which only the limbs are regularly wet and in which greater contact is unusal (e.g. boating, fishing, canoeing, rowing). There may be occasional and inadvertent immersion through accidents (e.g. slipping into the water).

The following alert system for blue green algae is included in the guidelines.


Permanent signs have been erected at various public use areas around Lake Tuggeranong, Lake Ginninderra and the Molonglo River. The signs are able to display LAKE OPEN FOR USE, WARNING, AREA CLOSED FOR PRIMARY CONTACT or LAKE CLOSED.

The location of the signs is shown on the maps below:

The guidelines identify the signage that should be used based on the following alert system for blue green algae.

Alert Levels

No Alert Level

No algae sighted.

Signage should read LAKE OPEN FOR USE.

Low Level Alert

At this alert level, there is generally no major health risk. Algal counts are less than 5,000 cells per millilitre of lake water (less than 0.4 mm3/L Biovolume).

Signage should read LAKE OPEN FOR USE.

Medium Level Alert

At this level, algal counts are between 5,000 to 50,000 cells per millilitre (0.4 to 4 mm3/L Biovolume) and scumming is ususally evident. There can also be a slight milky discolouration of the water and bright green surface scums.

Signage should read LAKE OPEN FOR USE.

When algal counts are above 20,000 cells per millilitre (1.6 mm3/L Biovolume) there is a greater risk of potential health problems. At this level and on advice from the Health Protection Service, the EPA issues media warnings; erects WARNING signs; alerts sporting groups such as yachting, rowing and swimming clubs, as well as organisers of water sport events; and notifies the Water Police.

Signage should read WARNING.

High Level Alert

At this level there is a higher risk of health problems. Algal counts are between 50,000 and 125,000 cells per millilitre (4 to 10 mm3/L Biovolume) and extensive scums have formed.

On advice from the Health Protection Service, the EPA may close recreational areas and the lakes for primary contact use. If the EPA closes a lake to primary contact because of the severity of the blue-green algal bloom, it will place AREA CLOSED FOR PRIMARY CONTACT signs around the lake; issue a media release; continue intensive monitoring until algal counts decrease to levels below 50,000 cells per millilitre of lake water; provide the community with regular reports about the condition of the lake or river recreation area; and communicate re-opening of the lake or waterbody for primary use by a media release.


Extreme Level Alert

At this level there is an extreme level of risk of health problems. Algal counts are above 125,000 cells per millilitre (greater than 10 mm3/L Biovolume), extensive scums have formed and environmental conditions suggest that algal numbers are likely to escalate quickly and become widespread throughout the water. The lake is closed for primary use and the risks assiciated with secondary contact use may be reduced provided steps outlined in the strategy are followed.


Water Quality Results (including Blue Green Algae and Bacteria)

Before engaging in water recreational activities, please ensure you check the most recent results.
The blue green algae results have been combined with the bacteria results and are now located on the TAMS website.

Water Quality Results (including Blue Green Algae and Bacteria)  

Bacteria Monitoring

The ACT Health Protection Service conducts monitoring for bacterial pathogens at a number of sites in Canberra's lakes, ponds and rivers on behalf of Territory and Municipal Services (TAMS). TAMS is responsible for warning the public if required. Any enquiries related to bacteria monitoring are directed to Access Canberra on 13 22 81.

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