Sydney Harbour water turns bright green after ‘bucket-full’ of dye gets into waterways

Locals say the water resembled ‘radioactive stuff you see in superhero movies’

Water in the Sydney Harbour in New South Wales, Australia, turned a bright green colour due to the spillage of a non-toxic fluorescent dye, authorities said.

Residents near the Careening Cove at Milson Park, Kirribilli, where one of the official homes of prime minister Anthony Albanese is located, were shocked to see the water turn green on Wednesday afternoon.

Locals reported a “large spill of fluorescent green material” to the authorities at about 3pm (local time), prompting the Fire and Rescue NSW to investigate the sudden colour change of the water.

Later, tests conducted by authorities found the substance to be a non-toxic and odorless chemical used by plumbers to dye water to find leaks.

Sydney harbour water turns green (Screengrab/ Guardian Australia)

"We can't say for sure but that's what we think it is," superintendent Adam Dewberry said, reffering to a chemical called fluorescein. "It's a common product that does get used to dye water and it's very effective," he told reporters.

The dye had come out of a storm drain in Kirribilli but the exact area where it entered the harbour remains a mystery as there were several access points to the stormwater systems.

"The main thing is we’ve identified it’s non-toxic," Mr Dewberry said, adding there have been no reports of marine damage or fish deaths. "... there’s no staining on any of the boats that are in the bay there, or around the wharves or the shoreline," he added.

A local described the water as resembling “green cordial” and the “radioactive stuff you see in superhero movies”, 9News reported.

Authorities flushed the drainage system which was clear of the green water by 6.40pm (local time).

Locals had also spotted a green colour in a stormwater drain at Anderson Park before the hue was spotted at a bigger part of the bay, according to reports.

The chemical which turned part of the bay green is used as a flow tracer to determine leaks, said Stuart Khan, a water expert and a professor of environmental engineering at the University of Sydney. “That’s its normal use. Clearly in this case it’s been misused ... It’s a massive amount. It’s probably a whole bucket full of fluorescein dye,” he told The Guardian.

Sydney is forecast to receive about 10mm of rain next week, which authorities hope would dissipate the discolouration.