See the ‘Port Phillip Bay’ page for a detailed description of the Bay.
This Report Card provides an overview of water quality in the Bay from 1 July 2015 to 30 June 2016. These scores are generated using a combination of five standard indicators: nutrients (nitrogen), water clarity (total suspended solids), dissolved oxygen, salinity and algae (chlorophyll-a).
Overall, water quality in Port Phillip Bay for 2015–16 was ‘Good’.
Summary Table: The table below shows the percentage of Port Phillip Bay that falls into each scoring category. See scoring method for more information.
Central Bay to the Entrance, including the eastern near-shore region
Corio Bay, Hobsons Bay and the western near-shore region to the Central Bay
Newport, directly downstream from highly industrialised activities
Routine monitoring is currently undertaken across six sites within the Bay.
See Monitoring Programs for changes to the monitoring program.
The section Changes over time compares the Bay’s annual index scores with scores from previous Report Cards (since 2002). Results can also be compared to other catchments.
The water quality score in the Bay for 2015–16 was ‘Good’, with 99 per cent of all scores in the ‘Good’ to ‘Very Good’ categories. This means water quality at almost all monitoring sites met marine water quality guidelines in 2015–16.
Within the Bay, the near-shore area at Carrum to the entrance had ‘Very Good’ water quality. The majority of the Bay had ‘Good’ water quality, from Hobsons Bay around to the western near-shore areas close to Werribee and Corio Bay. Water quality at Newport was ‘Fair’. No areas of the Bay had ‘Poor’ or ‘Very Poor’ water quality.
Water quality within the Bay for 2015–16 has been consistently good due to several years of low rainfall and decreased river discharges. However, salinity levels have slightly increased at most sites throughout the Bay, with the exception of Hobsons Bay and Newport at the mouth of the Yarra River. Improvements in water quality due to reduced river discharges were evident near the mouth of the Yarra and Patterson Rivers, as these areas had reduced levels of algae and clearer water. Throughout the central Bay area there was a small increase in nutrients and algae resulting in a slight reduction in water quality.
The southern area of the Bay, near the entrance, is well flushed with clean seawater by the tidal exchange that occurs twice a day. The water quality in this area is always ‘Very Good’.
Short-lived environmental and extreme weather events can impact water quality in the Bay. Heavy rainfalls in late December 2015 and again in early January 2016 resulted in stormwater impacting the near-shore environment. These impacts only lasted for a day or two, and did not affect the long-term water quality of the Bay.
An algal bloom occurred at Williamstown Beach in December 2015. The bloom only lasted one day and dissipated naturally.
Since 2002, water quality in the Bay has improved.
In years of drought (1995 – late 2009) and lower rainfall, improvements in Bay water quality were associated with decreased river discharges and catchment-derived pollutants and nutrients at locations near river mouths and stormwater outlets. Additionally, the extremely low rainfall led to an increase in the Bay’s salinity levels above the normal range. This was a consequence of insufficient freshwater flowing into the Bay to compensate for water lost though evaporation. This occurred in 2008 and 2009, towards the end of the drought, and was more pronounced on the western side of the Bay and through the Geelong arm.
In 2010, drought breaking rainfall fell over the Bay’s river catchments, increasing stream discharges and increasing the input of pollutants and nutrients at locations near river mouths and stormwater outlets. This resulted in a slight decline in the Bay’s water quality. Water quality around Newport and Hobsons Bay declined, and improvements occurred in Corio Bay and Long Reef as salinity levels returned to within the normal range.
From 2010 until 2013, a return to average climatic conditions resulted in a return to ‘Very Good’ water quality in 2013–14. A consistent decline has occurred since then due to low rainfall and reduced freshwater inflows, which has increased salinity levels throughout the western bay area. An increase in nutrients and algae throughout the central Bay area has also contributed to a decline in the Bay’s water quality.
The Government, authorities and community have implemented the following initiatives to improve water quality in the Bay:
In addition to the initiatives set out in the Yarra and Bay - Actions, a range of key initiatives are being undertaken by the Government and the community that aim to raise awareness and drive actions to improve water quality in the Bay. These include:
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.