Sydney’s largest dam was cut off from the water network on Monday amid fears it was too contaminated after heavy rains disturbed mud and bushfire ash.
The move was only revealed today when the dam was reconnected because the water was deemed safe.
After last weekend, sediment, ash, and debris from 320,000 hectares of burnt bushland was seen floating on the surface of the water near the dam wall – prompting the switch to use water from Prospect Reservoir.
There were also fears fire retardant could have washed into the water catchment.
NSW Water Minister Melinda Pavey confirmed the dam was cut off. ‘We just wanted to let things settle,’ she said.
Drinking water in Sydney is once again being drawn from Warragamba Dam (pictured) less than a week after authorities cut the supply over fears of contaminated water
‘Ongoing monitoring results confirmed confidence in the quality of water available from Warragamba,’ a Water NSW spokesperson said (stock image)
The dam, which holds 80 per cent of Sydney’s water, was reconnected on Saturday.
‘Ongoing monitoring results confirmed confidence in the quality of water available from Warragamba,’ a Water NSW spokesperson told the ABC.
An incident response team was established and is working with Sydney Water and NSW Health on further monitoring and contingency plans.
‘Raw water quality at Warragamba is improving, however, more inflows may cause further deterioration in water quality at the dam wall,’ Water NSW chief, David Harris, said.
Bushfire ash also contains nutrients such as nitrogen and phosphorous which can stimulate the growth of cyanobacteria also called blue-green algae.
Some cyanobacteria can produce toxic chemicals requiring careful filtration of the water before drinking.
Precautionary measures are being implemented such as floating booms to capture ash and silt.
Smaller water sources such as the Nepean and Tallowa dams were also topped up during the recent rains, however, level two water restrictions still remain in place in Sydney.
Authorities have also reminded the public water is treated between the dam and the household tap.
Recent bushfires in New South Wales have burnt hundreds of thousands of hectares of forests
‘It is important to note that this issue only concerns untreated water in dam storages at the beginning of the supply chain and has no impact on the quality of treated water,’ a spokesperson for Water NSW said.
Water filtration plants catch suspended particles in the water, however, an increase in these particles such as after a bushfire could cause the systems to struggle and clog filters.
Health authorities may issue a ‘boil water alert’ when there is a possibility water could be contaminated with microorganisms.
In cases where water may be contaminated with chemicals a ‘do not drink alert’ can be issued.
Most state health and water department website can contain information on alerts, Sydney Water, for example, offers a daily drinking water report feature on their website.
There are currently no warnings in place for drinking water in Sydney.
Recent heavy rains in New South Wales have washed bushfire ash and debris into water sources