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Port Phillip Bay

Bay and Catchments

Water quality index
Land Use




Water Quality Index

Very Good




Very Poor

Citizen Science Data

Citizen Science monitoring site

See the ‘Port Phillip Bay’ page for a detailed description of the Bay.

Report Card for July 2015 – June 2016

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.

Area Score

Very Good
Near-natural high quality waterways

Central Bay to the Entrance, including the eastern near-shore region


Meets Victorian water quality standards

Corio Bay, Hobsons Bay and the western near-shore region to the Central Bay


Some evidence of stress

Newport, directly downstream from highly industrialised activities


Under considerable stress


Very Poor
Under severe stress

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.

What does this mean?

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.

Bar chart showing WQI and indicator scores for Port Phillip Bay Bar chart of WQI and indicator scores for Port Phillip Bay.

The new EPA research vessel, Bar-ba-ka, in Hobson's Bay. Source: EPA Victoria The new EPA research vessel, Bar-ba-ka, in Hobson's Bay. Source: EPA Victoria

Filtering for chlorophyll and total suspended solids. Source: EPA Victoria Filtering for chlorophyll and total suspended solids. Source: EPA Victoria

Changes over time

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.

Plot of WQI history for Port Phillip Bay Plot of WQI history for Port Phillip Bay


What's happened?

The Government, authorities and community have implemented the following initiatives to improve water quality in the Bay:

  • EPA's water quality reports for the community have been expanded to include alerts about pollution, fish deaths and algal blooms. These are now reported via the website Yarra and Bay.
  • The revision of the Port Phillip Bay Environmental Management Plan was initiated in 2014–15 and continued into 2015–16. The review will re-set targets for the protection of the Bay.
  • EPA's summer litter campaign A cleaner Victoria is in your hands continued. The campaign encourages people to report litter thrown from vehicles via EPA's online reporting tool or mobile apps. It is specifically aimed at creating awareness about the impact of litter on our natural assets such as the Bay and its catchments.
  • Beach litter associated with stormwater inflows is also being addressed directly by councils and the Government through a range of litter management programs. Community stakeholders around the Bay in 2015–16 have continued to be active in beach cleaning programs such as Beach Patrol, to routinely collect and monitor litter in Port Phillip Bay.

What's planned?

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 Environmental Management Plan for Port Phillip Bay is being revised, with a focus on better managing pollution coming to the bay (particularly via stormwater) and its impacts on water quality
  • The State of the Bays Report – the Commissioner for Environmental Sustainability Victoria will release the first State of the Bay Report in late 2016. The 2016 State of the Bays Report will be the first of its kind and will provide a scientifically rigorous baseline report on the health of Port Phillip Bay and Western Port against which future reporting can be compared.
  • The Litter Innovation Fund, which includes support for projects that help reduce litter and illegal dumping in the Yarra River and Port Phillip Bay catchment.
  • Government-driven strategies for coastal protection and waterway improvements.
  • Community engagement programs such as Coastcare, from EstuaryWatch and Sea Search community-based monitoring.
  • Parks Victoria's Marine Natural Values ecosystem condition assessment reporting, which is currently being developed for marine parks across the state, including the four marine-protected areas (Jawbone, Point Cook, Rickett's Point and Port Phillip Heads) in Port Phillip Bay.

Compare to other Catchments

The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.

Diagram of nutrient score history for catchments and bay

Diagram of oxygen score history for catchments and bay

Diagram of water clarity score history for catchments and bay

Diagram of salinity score history for catchments and bay

Diagram of score history for catchments and bay

Diagram of metals score history for catchments and bay

Program Partners

Department of Environment and Primary Industries Environmental Protection Agency Melbourne Water