Blue-green algae (BGA) are simple aquatic bacteria (Cyanobacteria) that occur naturally in waterways such as creeks, rivers and still water habitats, such as dams.
Blue-green algae is always present, but when weather conditions are right for them to grow they can multiply into an algae ‘bloom’. It’s difficult to estimate when blooms will occur and when they will die off, although blue-green algae numbers tend to increase during summer and high temperatures. Untreated river or lake water should not be used for consumption, as boiling water does not remove toxins which may be produced by blue-green algae.
Bodies of water containing high numbers of blue-green algae may pose a health risk to humans when used for water-based recreation, such as swimming or water skiing. As blue-green algae numbers increase, so can the risk of adverse health impacts, so it is important to monitor blue-green algae levels.
The recreation hazard varies according to the types and respective amounts of algae present within the storage at any time.
For more information on blue-green algae, visit the Australian Water Quality Centre.
BGA – What it Means to your Water SupplyDownload
Blue-green algae levels
Sunwater regularly monitors and updates blue-green algae levels for its water storages.
The National Health and Medical Research Council (NHMRC) has established three hazard levels for storage operators and water users to assess the danger posed by blue-green algae during primary contact water recreation activities (i.e. swimming, canoeing, water skiing etc).
The following values are based on the NHMRC guidelines for safe practice in managing bathing waters which may produce or contain cyanobacterial cells and/or toxins.
≤ 500 to < 5000 cells/mL Microcystics aeruginosa or biovolume equivalent of > 0.04 to < 0.4 mm³/L for the combined total of all cyanobacteria.
≤ 500 to < 50 000 cells mL ¹ Microcystics aeruginosa or ≤ 0.45 to < 4 mm³ L ¹ for the combined total of all cyanobacteria where a known toxin producer is dominantª in the total biovolume or ≥ 0.4 to < 10mm³ L ¹ for the combined total of all cyanobacteria where a known toxin producer is dominantª in the total biovolume.
Level 1 guideline: ≥ 10μg /L total microcystins or ≤ 50 000 cells/mL toxic Microcystics aeruginosa or biovolume equivalent of ≥ 4 mm³ L ¹ for the combined total of all cyanobacteria where a known toxin producer is dominantª in the total biovolume.
Level 2 guideline: ≥ 10mm³ /L for the total biovolume of all cyanobacteria material where known toxins are not present or cyanobacteria scums are consistently present.
To view Blue-green algae levels, select a dam, weir or storage below.