The percentage of Port Phillip Bay beaches meeting all weather standards has been variable over time, likely due to changing rainfall patterns. Due to the impact that rainfall and stormwater runoff can have on water quality, more beaches meet water quality standards during dry weather.
Less beaches met dry weather standards during the 2018-2023 reporting period than in previous reporting periods. The 2018-2023 reporting period saw 3 La Niña events occurring across Australia, in 2020-2021, 2021-2022 and 2022-2023. La Niña events increase the likelihood of extreme rainfall and flood events. This has had extended impacts on the water quality in Port Phillip Bay.
Widespread flooding occurred across Victoria and the Greater Melbourne area in late October 2022. Large amounts of stormwater pollution and discoloured water entered the Bay, with water quality impacts continuing into January 2023. Water quality samples collected at that time may have been affected by the significant rainfall and flooding that occurred in the days or weeks prior to sample collection. This is likely to have influenced the percentage of beaches meeting long-term microbial water quality standards during the 2018-2023 reporting period.
Environment Protection Authority Victoria (EPA)'s advice is not to swim in Port Phillip Bay for 48 hours after rain, or longer if the effects of rainfall and flooding are still noticeable (for example stormwater drains are flowing, there is murky water, a bad smell, and rubbish present). EPA provides up to date information about where it is safe to swim on the Beach Report website and through a free SMS service. During periods of dry and stable weather, Port Phillip Bay beaches meet swimming standards on most days throughout the summer.
10 out of 36 beaches met long-term microbial water quality standards and were scored as either Good or Fair grades. All 36 beaches met long-term microbial water quality standards for secondary contact recreation. For more detail on how long-term microbial water quality grades are calculated view the methodology section.
Stormwater pollution after rain is the biggest influence on long-term microbial water quality. High microbial levels in stormwater pollution can increase the risk of illness during swimming. Some sites are more susceptible to stormwater pollution than others. It is difficult to predict which beaches will be impacted during and after isolated rain events. For this reason, as a precaution, the EPA advises avoiding any contact with water for 24-48 hours following rainfall.
Many beaches (15 out of 36) met long-term microbial water quality meeting standards for primary contact recreation during dry weather. 21 beaches did not meet standards, as they had elevated microbial levels during dry weather periods. For more detail on how long-term microbial water quality grades are calculated view the methodology section.
Dry weather grades and status use the same microbial data as all weather status, however data from samples collected during or after rainfall are removed.
The number of beaches not meeting long-term standards in the 2018-2023 reporting period was likely due to the extended water quality impacts from La Nina events and extreme rainfall. These beaches still had microbial water quality suitable for swimming on most days during summers. During summer, sampling results are assessed against short-term standards and advice is provided to community on whether water quality is suitable for swimming. High microbial results were infrequent at these beaches. Where high microbial results were found, follow up sampling showed that the microbial water quality improved by the next day.
For recent short-term results, see the EPA's publication: Beach Report and Yarra Watch results.
For more detail on how grades and status are calculated view the methodology section.
Page last updated: 17/04/24