Revealed: Sydney’s cleanest and dirtiest places to swim

Run-off from construction sites, dog poo on the streets, and sewage overflow is impacting water quality in Sydney Harbour, undermining a push to expand natural swimming sites throughout the city.

Water testing commissioned by The Sydney Morning Herald revealed elevated levels of faecal contamination at several sites around Sydney Harbour, with results for the bacteria Enterococci at Dawn Fraser Baths in Balmain 10 times the safe level on the day of testing.

Water quality was better out west, with good results at Lake Parramatta, Penrith Beach and Windsor Beach. Balmoral Beach on the lower north shore was also clean.

Several new harbour and river swimming sites have opened in the past three years, including Marrinawi Cove at Barangaroo under the former government, Penrith Beach or “Pondi” in 2023-24, and Putney on the Parramatta River last week. Late last year, the NSW government established a task force to find new sites, especially in western Sydney.

PhD candidate Katherine Warwick taking water samples at Marrinawi Cove, the public swimming spot at Barangaroo.Credit: Dylan Coker

The Parramatta River Catchment Group, which includes 14 councils and state government agencies and corporations, including the NSW Environment Protection Authority and Sydney Water, had a 10-year plan to make the river swimmable by 2025.

Mark Drury, a former inner west councillor and chair of the catchment group until September 2024, said one of the most stubborn problems was dog poo.

“The biggest problem in terms of the cleanliness of waterways is … dog poo,” Drury said. “It’s people not picking it up on the street, and it getting washed down the stormwater [drains] into the rivers. It’s the same for the Parramatta River and almost every urban river around the world.”

Another big contamination source, Drury said, was construction. The catchment group developed a program called Get the Site Right to help prevent run-off from building sites, both large and small.

Other contaminants include rubbish, cigarette butts, leaf litter, oil and bird droppings, said a spokesperson for the NSW Department of Climate Change, Energy, the Environment and Water.

Parramatta River is much cleaner than it used to be. Drury said the Clean Waters Act 1970 stopped industrial-level dumping in the river, and Sydney Water had invested heavily over the past decade to massively reduce sewage overflow and leakage in the catchment.

A Sydney Water spokesperson said it would spend $30 billion in the next 10 years to upgrade and expand its water and wastewater networks across the state.

The Herald collected samples on November 22 and January 6, and the testing was done by Katherine Warwick, a PhD candidate in aquatic ecology at Western Sydney University. The sites selected were popular swimming spots, including several places not covered by the state government’s Beachwatch program.

The results show the level of Enterococci bacteria, which live in the guts of warm-blooded animals and can cause severe gastrointestinal illness. Enterococci are an indicator of faecal matter in water and often occur alongside another serious pathogen, E. coli, though the testing did not cover this.

The samples were taken after several days of clear weather, in line with public health advice to avoid swimming in the harbour and rivers for three days after rain.

The worst results were for Dawn Fraser Baths, a heritage-listed harbour pool in Balmain built in the 1880s and refurbished in 2021. The average of two samples taken from deep water at the end of the central pontoon on January 6 was 413.25 Enterococci (ENT) colony-forming units (cfu) per 100ml.

National Health and Medical Research Council (NHMRC) guidelines say recreational swimming is safe when ENT cfu/100ml is below 41. Many of the Sydney Harbour swimming sites, including Barangaroo, Murray Rose Pool (Redleaf) and the newly reopened Nielsen Park, tested in the 41-200 range, above the threshold for illness transmission.

Warwick said this was “definitely concerning”.

“I’d be questioning whether to put my head under [the water] in a spot that regularly sees readings between 41 and 200,” she said.

Dawn Fraser Baths and the average of samples taken at nearby Mort Bay were in the 201-500 range, which NHMRC advises is a “substantial elevation in the probability of adverse health outcomes”. Balmain residents have long swum at Mort Bay informally, and Inner West Council has flagged it as a future official swim spot, along with Callan Park.

A department spokesperson said the Beachwatch program had operated since 1989 and was expanded this season to cover more inland and regional places.

The program conducts weekly testing in the summer. Some estuarine sites are monitored monthly in winter, while Sydney’s ocean beaches are tested weekly year-round.

Water testing is always retrospective because it takes 24 to 48 hours to grow the bacteria in lab conditions. Beachwatch issues pollution advisories twice a day, using rainfall to predict likely pollution at various sites with a traffic-light system of red, amber and green.

Professor Stuart Khan, head of the engineering school at the University of Sydney and chair of the NHMRC Recreational Water Quality Advisory Committee, said work was under way to update the guidelines to enable a proactive assessment based on risk factors.

“We need more of a risk management framework where we’re not relying on taking retrospective water-quality samples and saying, ‘well, people probably shouldn’t have swum there yesterday’,” Khan said.

Back in 2021, City of Sydney Lord Mayor Clover Moore shared plans for more swimming sites around the harbour if pollution levels could be managed.

Moore said she was keen to deliver but would not install infrastructure, including nets, until water quality reached an acceptable level.

“As a government authority, we can’t responsibly encourage more swimming while we know the water quality isn’t safe.”

“Given the age of sewer pipes in the inner city and pollution levels from past industrial uses, raising the water quality to a sufficient level for safe swimming will require significant investment by Sydney Water and the state government.”

Beachwatch gives Dawn Fraser Baths a “good” annual grade, meaning it is suitable for swimming most of the time except after rainfall. Its regular testing for the Balmain pool recorded a squeaky-clean ENT cfu/100ml of 1 on January 2 and zero on January 15.

Inner West Mayor Darcy Byrne said if the Beachwatch pollution advice was red, the council closed the pool. For an amber alert, it put out signage to alert customers, including a QR code for more information.

The pool was open with an amber warning on January 6. Despite a storm later that evening and wet weather the following days, the pool remained open at amber alert for two more days.

By the time the pool closed on January 9 because of a red alert from Beachwatch, the official testing had an enormous 1200 cfu/100ml.

Byrne said he was concerned the Herald test suggested the pool should have been closed on January 6, and he would write to the state government to question the discrepancy.

Multiple entities, including state government agencies, local councils and Sydney Water, share responsibility for water quality in waterways, both the Department of Environment and Sydney Water confirmed.

Byrne said this structure was part of the problem, though the catchment group had done good work to bring everyone together.

“One thing I learned from the asbestos mulch saga is that whenever there are multiple government agencies responsible for something, it means no one is responsible,” he said.

“We can’t have inertia between agencies undermining public safety or confidence in the world’s most beautiful harbourside pool.”

Penrith Beach, in a former quarry on the Nepean River, was the cleanest natural swimming site tested by the Herald. On January 6 it was about 33 degrees and at least 100 people were swimming, yet the average of two samples taken that day was only 3.5 ENT cfu/100ml.

At Lake Parramatta, the Herald testing on November 22, soon after it opened for the season, registered 28.5 ENT cfu/100ml, well within the safe threshold.

The dammed creek, which flows into the Parramatta River, first opened for swimming in 2015 and was upgraded last year with a new lifeguard platform and gently sloping beach entry.

A City of Parramatta spokesperson said the council took “great pride in maintaining the water quality at Lake Parramatta” and conducted regular tests.

The Herald tested two council swimming pools for comparison – the old-school Victoria Park Pool in the City of Sydney and the shiny new Parramatta Aquatic Centre – and both recorded an ENT cfu/100ml reading of zero.

Warwick said this was reassuring, though expected, since chlorine killed the bacteria. As a former lifeguard, she was involved in issuing “code browns” to evacuate swimmers when a child had an accident at a council swimming pool.

Warwick said she was “stoked” by the good results in western Sydney. She said natural swimming spots were important for many families who could not afford the entry price at council pools.

“These freshwater sites are becoming a heat refuge for a lot of people,” Warwick said. “As our climate warms and as the cost-of-living crisis continues to worsen, these sites will become increasingly popular.