Swimmers told to stay away from Port Phillip Bay beaches as floods contaminate waterways

Residents living around Melbourne’s Port Phillip Bay are being urged to avoid swimming at the beach as Victoria’s ongoing floods continue to contaminate waterways.

Victoria’s Chief Environmental Scientist, Mark Taylor advised on Tuesday that microbes had made their way into waterways after heavy rains, bringing the risk of pollution (including faecal matter), mosquitoes and water-borne diseases.

To investigate the risks of pathogens and sewerage levels in the water after widespread and ongoing flooding, Victoria’s Environment Protection Authority has launched a “high quality” sample analysis program at 19 Victorian sites, including nine waterways.

Taylor said it was the “single most comprehensive” assessment of water quality and the pathogen E coli that had been undertaken in Australia’s history, advising “when the whole land is inundated, it will inundate, release and mobilise sewage, which is why we’re measuring for E coli.”

The bacteria, which normally lives in the intestines of humans and animals, can cause faecal contamination in water which can lead to severe stomach cramps, diarrhoea and vomiting.

The water samples, collected by the State Emergency Service, showed the presence of faecal matter in all waters at generally low levels.

Only the water tested at Shepparton showed very high levels of the faecal bacteria. The Goulburn River tested at 2,000 Most Probable Number per 100 ml, compared with the guideline of 550.

As heavy rainfall and widespread flooding throughout October stirred up sediments and contaminated water systems, the EPA issued an alert warning that no beaches around Port Phillip Bay were considered suitable for swimming.

The EPA advises against swimming at all waterways and beaches 48 hours after heavy rain, and “much longer” in the event of floods due to the risk of illnesses like gastro and diarrhoea.

11 beaches were rated “poor”, including the popular St Kilda beach and Elwood, while a further 25 sites had been issued with an alert for possible stormwater pollution. The warnings were likely to be in place for at least a week.

Poor water quality and stormwater pollution had also been detected along the Yarra River at Launching Place, Healesville, Warrandyte and Kew.

Taylor said despite recent sunshine, finding “alternative solutions” to cool off and keeping pets out of the water was important until rainfall eased.

He added “the water quality is not tip top, we’re encouraging people to stay out until we really see it as clean and presenting as suitable to swim in.

“The Yarra River is understandably still poor, and it will be until later on into the summer as the effects of floods dissipate.”

The popular Mornington Peninsula beach spots Blairgowrie, Rye, Rosebud, Dromana, Safety Beach, Mount Martha, Mornington and Canadian Bay were all under alerts for possible pollution, as were parts of Frankston, Kingston, Bayside, Port Phillip, Hobson Bay, Wyndham, Greater Geelong and Queenscliffe.

Taylor said discoloured water and foam were obvious signs of pollution, as were algae blooms and bubbles which could act as an irritant, particularly for people with asthma.

The Bureau of Meteorology recorded rainfall totals of up to 100mm across much of the Murray-Darling Basin in the past week, while at Kenley near Swan Hill, residents were urged to evacuate on Monday afternoon amid major flooding.