Department of Primary Industries – Water Key to blooms (Australia)
Red alerts are declared where algal cell numbers exceed the triggers identified in the Guidelines for Managing Risk in Recreational Waters released by the National Health and Medical Research Council.
All blue green algae ‘blooms’ should be considered as potentially toxic to humans and animals, and the water should not be used for potable water supply (without prior treatment), stock watering, or for recreation. NSW Health advises that any domestic use (including drinking) of surface water without treatment should be avoided at all times.
Red .These alert levels represent ‘bloom’ conditions. The water will 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 potable water supply (without prior treatment), stock watering, or for recreation.
Amber. Blue-green algae may be multiplying in numbers. The water may have a green tinge and musty or organic taste and 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.
Green. Blue-green algae are first detected in the water at low amounts, possibly signalling the early stages of the development of a bloom. At these concentrations, the blue-green algae do not pose a threat to recreational, stock or domestic use.
KEY TO BLOOMS To help in the identification of scums and growths, a simple key can be used. Follow the steps using the pictures to find if the scum is possibly caused by a blue-green alga, another alga or by an aquatic plant. It is necessary to go to the surface of the scum to do some simple tests.