Environment Protection Authority Victoria (EPA) has released its top beaches for the summer of 2016-17 with Eastern Beach, The Dell, Portarlington and St Leonards tied at the top of EPA’s water quality forecast rankings.
Portsea, Blairgowrie, Sorrento and Santa Casa were next in line, with Dromana and Rosebud sitting equal tenth in the final wash-up of the 36 Port Phillip Bay beaches (PDF 60KB) EPA provides water quality forecasting for during the warmer months.
During summer, EPA provides twice-daily forecasts for beaches of either good, which equates to suitable swimming conditions, fair, meaning beaches may not be suitable, or poor, which advises beaches are not suitable for swimming.
EPA Applied Sciences Group Manager Anthony Boxshall said heavy periods of rain had kept EPA scientists on their toes over the summer, as precipitation of more than 10 millimetres was often associated with poor water quality at Port Phillip Bay beaches.
“While it was quite a dry summer, Victoria experienced prolonged downpours around the Christmas / New Year’s period that contributed to extended periods of poor water quality at all of the 36 beaches that EPA monitors,” Dr Boxshall said.
“Unfortunately for beachgoers, most of this rain fell just before or during weekends, and usually just before warmer weather, which is when Port Phillip Bay beaches are at their busiest.”
Dr Boxshall said that the storms meant EPA forecast poor water quality conditions at beaches for eight per cent of the time in summer, with 15% of forecasts fair and 77% good.
“This compares to the 2015-16 summer where we had 6% poor, 19% fair and 75% good. However, this two percentage point difference was an increase of about 200 poor forecasts over the summer, and occurred mostly at peak times of beach use,” Dr Boxshall said.
“These figures are not surprising given we saw about a 10% increase in rain captured during the 2016-17 summer at six rain gauges spread around the fringes of Port Phillip Bay when compared to the previous summer.”
Dr Boxshall said that a combination of Melbourne’s stormwater system and the downhill nature of the landscape towards Port Phillip Bay meant that heavy rain flushed anything on suburban streets into stormwater systems and straight into the Bay.
“Eight major creeks and rivers, and more than 300 drainage outlets flow into Port Phillip Bay. Sources of this water include about 5,000 underground drains that collect Melbourne’s runoff,” Dr Boxshall said.
“From there, about 540,000 million litres of stormwater containing around 160,000 tonnes of sediment washes into the Bay annually; and remember that the Bay itself is only about 25 cubic kilometres.”
Dr Boxshall said that looking at such huge numbers showed just how resilient the beach water quality of Phillip Bay is to be able to bounce back to its normal state, on most occasions, within 48 hours.
“The Bay is able to do this because of both biological and physical processes that work together to return the Bay to good beach water quality conditions. The action of the tides and currents moving around is one important physical process to dilute pollution at beaches,” Dr Boxshall said.
“A contributing biological factor that helps breakdown pollution is the amount of sun that follows heavy rainfall; sunny periods can help break the bugs down that cause stormwater pollution quite quickly. However, the sun can also create perfect conditions for algal blooms, which we saw plenty of early in January.”
Dr Boxshall said that these were reasons why EPA always advised people to avoid swimming near any stormwater or river outlets 24-48 hours after rain or in areas where water was discoloured, or debris, oil and scum visible.
“This advice holds true for all waterways right across Victoria,” Dr Boxshall said.
Dr Boxshall said that the community could help improve Port Phillip Bay water quality by ensuring they use qualified plumbers to make sewer connections, avoided littering, and swept grass cuttings and garden waste up.
“EPA, together with the community’s help, water authorities and industry, is continually working to improve our drainage and sewer systems to lessen the pollution burden on Port Phillip Bay,” Dr Boxshall said.
EPA issues twice-daily water quality forecasts of good, fair and poor for Port Phillip Bay’s 36 beaches online at www.yarraandbay.vic.gov.au and via twitter @EPA_Victoria during summer.
EPA also issues forecasts for popular Yarra River locations in Kew, Warrandyte, Healesville and Launching Place.