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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 in our Newsroom.

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.

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

Macintyre River at Malgarai (Boggabilla) - Blue green algae identified at this site pose a moderate risk to livestock. Where possible alternate sources of water should be sought.

A Red Alert is also in place for Walka Water Works in Maitland.

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 of Microcystis aeruginosa are present or a biovolume of all toxin producing cyanobacteria exceeds 4 mm3/L. A red alert level is also triggered if the total of all blue-green algae (toxic and non-toxic) exceeds 10 mm3/L or scums are present for long 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 of all blue-green algae is between 0.4 and 4 mm3/L. At this alert level investigations increased sampling of algae is undertaken.

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 blue-green algae 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.

About algae

Algae is a natural part of the aquatic ecosystem with most species safe or non-toxic. However, some algae can produce toxins that can be damaging to humans, domestic animals and livestock that drink or come in contact with the water, and also organisms living in water. These algae can be found in freshwater as well as marine and estuarine waters.

Blue-green algae (also known as cyanobacteria) are the only group of algae known to be toxic in freshwaters. They are microscopic bacteria living in water, and are capable of photosynthesising which is why they are often called algae. Though microscopic, when they form colonies and accumulate together they can become visible to the naked eye. Blue–green algae can produce potent liver and neurotoxins as well as skin irritants. However, not all blue–green algae are toxic, and even toxic species do not always produce toxins.

Many blue-green algal species are able to regulate their buoyancy and can sometimes be seen as green scums on water, or they just colour the water green. See Key to Blooms for more information on identifying blooms.

Toxic marine and estuarine algae can also affect recreational water use. Some of these algae produce toxins that can cause illness, particularly if contaminated shellfish is ingested, and others can cause skin irritations. These algae often cannot be seen, but some cause red discolouration to water a phenomenon known as red–tides.

  • Co-ordinate and support Regional Algal Co-ordinating Committees (RACCs)
  • Contributes to the State Algal Advisory Group (SAAG).
  • Contributes to the Regional Algal Management Guidelines.
  • Manages algal communications including hotline, media enquiries, website and briefings to Minister.
  • Monitors rivers and storages to service those aspects of the RACC’s reporting requirements, in accordance with the RACC Guidelines and WaterNSW Service Provision Deed.
  • Take a lead role in managing the risk of algal blooms in fresh waters by coordinating algal monitoring, management and public information (media and web based information) in surface waterways and storages where no other management organisation has a role.
  • Liaise with other agencies affected by algal blooms in order that an integrated risk management approach is taken.
  • Perform a knowledge broker role and facilitate communication between regional stakeholders and the State body responsible for algal management
  • Identify knowledge gaps and encourage research to provide new information to enhance algal monitoring and management.
  • Co-ordinate and manage regular algal information on behalf of stakeholders and ensure that water users and other stakeholders are informed.


Monday 21 October
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Monday 21 October