Potential changes to monitoring

In relation to COVID-19 WaterNSW are continually monitoring the state-wide and national government responses and acting accordingly to follow advice and implement required practices. Due to the recommended restrictions on non-essential travel WaterNSW will regularly review the necessity for travel and data collection across the state. This may result in a reduction of sampling and testing for some sites that are no longer deemed critical in regards to recreational use.

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Alert information

For information on current recreational alerts see the status reports below, call the NSW algae hotline on 1800 999 457, or view the media releases on our Alerts and update page.

Algal blooms can cause waters to be unsafe for recreation in both freshwater and marine water environments. Algal alerts are issued by Regional Algal Coordinating Committees (RACCs) who are responsible for local management of algal blooms. Algal alerts reported on this web page are for recreational water use.

Current Algal Alerts

The below algal alerts map displays all current alerts collated by the RACCs across NSW. Algal blooms may be present and not reported to the RACCs. This map does not contain data from water storages managed by water supply authorities where there is no public access. Water users should use caution and be aware of signage placed around waterbodies, particularly during the warmer months.

NSW Health advises that any domestic use (including drinking) of surface water without appropriate treatment should be avoided at all times.

NSW Food Authority provides information regarding the impacts of blue-green algae on consumption of food, including all seafood, and within primary production industries.

Algal alerts in NSW map

Please click on a site to view additional algal alert details across New South Wales. Use the search bar to search for a site, address or other location. Click the basemap tool to toggle between aerial photography and other topographic layers.

Alerts are declared where algal cell numbers exceed the triggers identified in the Guidelines for Managing Risk in Recreational Waters (1.2MB PDF) published by the National Health and Medical Research Council (NHMRC 2008).

Additional advisory

  • Caution Alert: Berowra Creek estuary currently has areas of harmful algal blooms. They present as a red discolouration in the water. Recreational uses should avoid impacted areas.

Alert level definitions

Red alert levels represent 'bloom' conditions. The water may appear green and may have strong, musty or organically polluted odours. Blue-green algae may be visible as clumps or as scums. The 'blooms' should be considered to be toxic to humans and animals, and the water should not be used for drinking (without prior treatment), stock watering, or for recreation.

A red level alert is in place when >50,000 cells/mL of Microcystis aeruginosa are present or the biovolume exceeds 4 mm3/L where toxin producing cyanobacteria are dominant (>75%), or biovolume exceeds 10 mm3/L where toxin producing cyanobacteria are not dominant (<75%). A red alert level is also triggered when scums are present for extended periods.

At red alert level a waterbody should not be used for primary recreation. Waterbody managers should notify the public through signage and media avenues. Results should be forwarded to the appropriate Regional Algal Coordinating Committees (RACCs) for further dissemination and assistance in management of blooms.

At amber alert levels blue-green algae may be multiplying in numbers. The water may have a green tinge and musty or organic odour. The water should be considered as unsuitable for potable use and alternative supplies or prior treatment of raw water for domestic purposes should be considered. The water may also be unsuitable for stock watering. The water remains suitable for recreational use, however algal concentrations can change rapidly. Water users should use caution and avoid water where signs of blue-green algae present.

Amber level alerts are triggered when Microcystis aeruginosa concentrations are between 5000 and 50,000 cells/mL or the biovolume is between 0.4 and 4 mm3/L where toxin producing cyanobacteria are dominant (>75%), or 0.4 and 10 mm3/L where toxin producing cyanobacteria are not dominant (<75%).

At this alert level increased sampling of algae is advised.

At green alert levels blue-green algae are present in the water at low densities, possibly signalling the early stages of the development of a bloom, or a period where a bloom is declining. At these densities, the blue-green algae do not pose a threat to recreational, stock or domestic use.

A green level alert occurs above 500 cells/mL of Microcystis aeruginosa or >0.04 mm3/L of total cyanobacteria biovolume but below the amber alert level.

At this level routine sampling for algae should be undertaken.

For marine and estuarine blooms

The NHMRC algae guidelines for coastal waters for recreational uses are only based on a few species due to limited knowledge on toxic algae. Red level alerts are triggered when Karenia brevis levels exceed 10 cells/mL or when Lyngbya or Pfiesteria species are in high numbers.

A caution alert may also be issued where highly visible blooms elicit public and media inquiries and samples have not been identified or have been identified as non-toxic species.


Saturday 24 October
2,415,570 ML
2,581,850 ML
10,111 ML
1,445 ML
-7,153 ML
Saturday 24 October