EPA issues ‘blackwater’ alert to Northern NSW

By Melissa Coade

Tuesday April 6, 2021

Desperately seeking a mask… (Image: Adobe/Toby)

Odours reminiscent of rotten egg gas, and discoloured water have been flagged by the EPA as a possibility for coastal NSW following the extreme weather conditions of the past weeks

According to Adam Gilligan, the combination of recent rain, floods and dead fish could lead to some bad smells and discoloured water for the Northern NSW region but there is little the EPA can do about it. 

Mr Gilligan, who is a regulatory operations director at the EPA, explained that while ‘blackwater’ (where the decomposition of organic matter depletes oxygen and releases tannins) is a natural process, stagnant water and fish deaths could add to the unpleasant odour coming from the waterway.

“The recent significant rain elevated water levels in many rivers. 

“As the floodwaters moved over low-lying areas surrounding the rivers, they picked up large quantities of organic matter, including decaying vegetation and leaves, as well as dirt, sand and other debris,” Mr Gilligan said.

“Blackwater after flooding is a natural feature of Australian river systems and the capacity to prevent and manage the impacts of blackwater is limited,” he added.

The EPA has identified low oxygen levels in water samples taken from the Hunter River from Raymond Terrace to Sandgate last week. The samples, obtained by scientists on Tuesday 30 March, found the presence of dead fish and odours in the river. 

It is the low oxygen levels in the water that likely cause fish deaths, however after a period of heavy rain the risk to humans from other harmful chemicals or infectious organisms is significant. Mr Gilligan warned any person who chose to swim in the river to avoid swallowing the water. 

“Entering river water after heavy rain increases the risk of injury and infection.

“If you have swallowed river water and become ill, seek medical advice,” he said.

The EPA is supporting local councils and other government agencies with advice and further sampling of flood waters. 

“We encourage the community to be patient and to make contact with the EPA if they have concerns about polluted waterways in their area,” Mr Gilligan said. 

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