Blue-green algae Red Alert for Malpas Dam
WaterNSW has issued a Red Alert for high levels of potentially toxic blue-green algae at Malpas Dam, south-east of Guyra.
The alert applies only to untreated water at the identified location and will remain in place until monitoring confirms the risk has eased.
Potentially toxic blue-green algae can cause gastroenteritis if consumed. Contact with affected water may result in skin and eye irritation, while ingestion of algal toxins can lead to liver damage and other health issues. Anyone who believes they may have been affected should seek medical advice. Pets and livestock should be prevented from drinking contaminated water. Boiling water does not deactivate algal toxins.
Blue-green algae occur naturally and can multiply rapidly in still or slow-moving water when sunlight and nutrient levels are high.
WaterNSW advises the public to exercise caution when entering any waterway in NSW. These waters are untreated, water quality can vary, and conditions may change quickly. All untreated water should be regarded as unsuitable for drinking.
For information about the management of blue-green algae risks in treated drinking water supplies, visit your local council or water utility website.
Updates on blue-green algae blooms and Red Alert warning areas are available at www.waternsw.com.au/algae or via WaterInsights
Armidale – Malpas Dam
https://www.wioa.org.au/conference_papers/2011_vic/documents/Craig_Jakubowski.pdf
Armidale Water Treatment Plant (WTP) has a treated water production capacity of 40 ML/d and comprises coagulation, flocculation, sedimentation, monosand open gravity filtration, fluoridation and chlorination. Raw water is sourced from Malpas Dam. Characteristics of the raw water are provided in Table 1. Cyanobacterial events in Malpas Dam are common, with generally at least one bloom occurring per year. Generally the events occur between November and March, however high levels of cyanobacteria have been recorded as early as August and persisted at times until July.
During the algal blooms, contamination of the raw water source with taste and odour compounds is common, and at times algal toxins have been detected. Recently the predominant genus is Anabaena circinalis, which is capable of releasing the neurotoxin Saxitoxin. Algal counts in the order of 1.75 x 106 cells/mL of Microcystis aeruginosa and 4 x 106 cells/mL of Anabaena circinalis have been recorded. High levels of Microcystis aeruginosa in Malpas Dam in the 1980s were linked to liver damage in the Armidale community [1]. The primary taste and odour compound of concern from Malpas Dam has been geosmin, with levels as high as 1000 ng/L measured.
Red alert at Malpas Dam as algae blooms
Jan 17 2015
https://www.armidaleexpress.com.au/story/2800785/red-alert-at-malpas-dam-as-algae-blooms/
BLUE-green algae levels at Malpas Dam are at red alert with the dam gripped by a “bloom”.
Residents are being urged to limit their recreational use of the dam, which is Armidale’s main supply of water.
An Armidale Dumaresq Council spokeswoman said the bloom did not affect tap water.
“The water treatment process takes all of that out [of the water] so it is safe to drink,” she said. “In terms of recreational use, you can use it if you really want but it won’t be very pleasant.”
The algae may be toxic to humans so contact should be avoided.
It can cause skin and eye irritation and stomach upset if consumed without being boiled or treated.
The alerts are based on how many cells are present in a millilitre of water.
A red or high alert means there are more than 50,000 cells present.
Amber or medium is between 5000 and 50,000, and the lowest green alert is 500 to 5000.
The levels often varied and it was not unusual for blooms to occur.
“As the dam levels are lower and it has been warm we have seen the levels of blue-green algae increase,” she said.