Multiple beaches across Sydney have been declared unsuitable for swimming after a recent deluge flushed pollution into the water.
Key points:
- More than 20 beaches and pools in Sydney are "possibly" or "likely" contaminated
- Heavy rain has inundated drains with sewage which has flowed into nearby beaches.
- Beachgoers are urged to check Beachwatch online for the pollution forecast
Beachwatch NSW, which monitors water quality, said heavy rainfall has inundated drains and water mains with contaminants which has subsequently overflowed into the harbour and nearby surf beaches.
According to Beachwatch's online map, several popular beaches and pools in Sydney are listed as unsuitable for swimming due to "likely" contamination.
"A large number of swimming sites in the Sydney and Central Coast regions may be impacted by stormwater pollution today," the organisation said Friday morning.
Sydney spots that are affected include Parsley Bay, Rose Bay Beach, Murray Rose Pool, Hayes Street Beach, Balmoral Baths, Davidson Reserve, Woodford Bay and Cabarita Beach to the north.
To the south of the city there's Congwong Bay, Frenchmans Bay, Yarra Bay, Foreshores Beach, Silver Beach and Sandringham Baths.
A caution has been issued for Bronte Beach, Malabar Beach, Little Bay Beach and Tamarama Beach, which have "possible" pollution.
Weekend beachgoers have been encouraged to check the Beachwatch website for the latest forecast before heading to the water.
Most water contamination is the result of sewage leaking into stormwater drains during intense wet weather or old water mains.
Waters are tested for bacteria known as enterococci to determine faecal contamination.
Swimming in water contaminated by faecal matter can expose you to disease-causing microorganisms which can make you ill.
Western Sydney University water scientist associate professor Ian Wright said the amount of sewage being generated by the bulging population living along the coastline was a contributing factor.
"For those beaches, I'm thinking particularly of the city beaches – Bondi, Bronte, Coogee – if you look around you see lots and lots and lots of units, it's very intense," he said.
"Each person generates about 200 litres of sewage a day – the kitchen, the bathroom, washing machines et cetera – and our sewer mains were often built when we didn't have that population.
"And in wet weather, water gets in, it also leaks out, and Beachwatch know mathematically with rain, water quality is much worse, much of that is the leaking sewage coming into the stormwater and then into our beaches."
Waters to the west less safe
Dr Wright said the issue was even worse in inland waters west of Sydney and warned the public against swimming in creeks and rivers in urban areas.
"Anything that's close on the ocean, close to the heads of Sydney, is much better," he said.
"Creeks and the harbour, particularly west of the harbour bridge, it'll take several days for that to clean up."
He referred to Penrith Beach, as an example, which has "got the early stages of blue-green algae at the moment".
"It's safe, but it's something that they're monitoring carefully, as they are the Nepean River," he said.
"And this is a really big problem right around the world in our fresh waters. Less of a problem in the ocean, salt water and tides are better at dissipating the nutrients the algae feed off."
Dr Wright urged those looking to go for a dip in the coming days to check Beachwatch online and monitor the pollution forecast.