Sydney Harbour turns muddy brown as Australia sees torrential rains and flooding

Torrential rain and subsequent flooding caused Sydney Harbour's shimmering blue waters to turn muddy brown. The change was caused by overflowing wastewater systems and stormwater carrying soil and debris into the harbour.

The authorities have now urged swimmers to stay away as the effects could last for days. The New South Wales (NSW) environment department has also issued pollution warnings for all beaches in the region.

"Avoid swimming if you can see signs of pollution such as discoloured water and floating debris. Always check with lifeguards for the latest beach conditions," read the advisory.

"Due to extreme wet weather conditions and flooding events, stormwater pollution may be impacting some swimming sites," it further added.

The warning came after two weeks of continuous rains left several parts of Australia's east coast inundated with waters. The rains subsided only last week.

Meredith Campey, the manager of the NSW government's Beachwatch program, said that it was not just stormwater that had caused the change, but murky waters from flood-affected inland areas have also contributed to the muddy appearance.

She further stated that places like Pittwater, Sydney Harbour and Botany Bay have been the worst affected.

"One of the reasons it looks particularly bad now is because the degree of flooding would have caused a lot of erosion in gardens and parks," said Stuart Khan, the director of the graduate school of engineering at the University of New South Wales, told The Guardian.

"I would be wary until it's visually clear. The recommendation is usually three days but if it's still brown after a week I wouldn't be swimming in it," he added.

Several social media users shared the aerial footage of the harbour's muddy brown waters. "Wow, flying into Sydney is usually a magnificent sight," wrote one of the users.

Another user wrote: "I don't think I've ever seen Sydney Harbour this brown and full of muddy flood-waters. Also - looks like North Sydney Pool is building itself."

The change has been especially shocking to people because Sydney's waters are normally a sapphire-blue colour on a fine sunny day.