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Port Phillip Bay and Catchments

The Port Phillip Bay, Western Port and Gippsland Lakes Report Card was developed to report on the water quality at sites in Port Phillip Bay, Western Port, the Gippsland Lakes and their surrounding catchments. Click on the map or list below to explore.

Included on the map are the locations of water quality monitoring sites used in the calculation of the catchment Water Quality Index (WQI) scores and the location of monitoring sites of the Citizen Science Waterwatch program. Note: Waterwatch data is not used in the calculation of the catchment WQI scores.

Click on a site to see further information.

Bay and Catchments

Water quality index
Land Use




Water Quality Index

Very Good




Very Poor

Citizen Science Data

Citizen Science monitoring site

Report Card for July 2016 – June 2017

This Report Card provides a snapshot of water quality in Port Phillip Bay and its associated catchments from 1 July 2016 to 30 June 2017. The quality of the water is given an overall score by combining the results of a number of standard water quality parameters: nutrients, water clarity, dissolved oxygen, salinity, pH, metals and algae.

Over the 2016–2017 year, water quality in Port Phillip Bay and the Yarra River has marginally declined. Improved water quality occurred in the Maribyrnong, Werribee and Mornington catchments and conditions were maintained in the Dandenong catchment.

Summary Table: The table below shows the percentage of Port Phillip Bay and surrounding catchments that fall into each scoring category. See the scoring method for more information.

Area Score

Very Good
Near-natural high quality waterways

Forested upper catchments and southern area of Port Phillip Bay


Meets Victorian water quality standards

Upper catchments and northern and western area including the Geelong Arm of Port Phillip Bay


Some evidence of stress

Mostly the main rivers and tributaries in the rural mid-catchment areas


Under considerable stress

Mostly lower reaches of the main rivers and urban tributaries


Very Poor
Under severe stress

Mostly small urban tributaries


In 2016–2017, routine monitoring occurred across 110 sites in Port Phillip Bay and associated catchments. This represents 79 per cent of the total catchment area. The remaining 21 per cent of the catchments, which were not monitored, are mostly rural areas and would typically score as ‘Fair’.

The section Changes over time compares the 2016–2017 Report Card scores and indicators for the catchments and Port Phillip Bay to previous Report Cards (since 2000). More detail on the specific catchments and Port Phillip Bay is provided in their individual reports.

Site-specific details within Port Phillip Bay and each catchment can also be accessed directly from the map or within the individual catchment and Bay reports.

How did rainfall impact on water quality?

See the Water Quality Index section for information on general water quality trends and sources of pollution.

Changes in rainfall can have a significant impact on water quality. In 2016–2017, rainfall across the region was above average in all catchments, with the exception of Mornington.

It was the wettest spring since 2011 in the northern and western suburbs, and the wettest since 2013 in the eastern and southern suburbs. During summer, rainfall across Melbourne was mostly average tending to above average in parts of the east, and in autumn of 2017, rainfall in the Melbourne metropolitan area was generally close to average.

These wetter conditions generally improved river flow. In the Werribee and Maribyrnong catchments, flows returned to waterways in the upper catchments that had reduced to isolated pools or dry river beds, resulting in improved water quality. The rural streams of the mid catchment also showed overall improvements in water quality, despite having slightly higher levels of sediment and nutrient inputs, the improved stream flow reduced salinity levels.

The Yarra catchment was the only catchment to show an overall decline in water quality, which was associated with increased runoff to tributaries in rural areas of the mid and upper catchment. These small waterways tended to show high levels of nutrients and sediment. This was primarily due to runoff from their modified catchments coupled with their small size leading to increased levels of contaminants.

The return to average and above average rainfall in the catchments reduced some aspects of water quality in Port Phillip Bay. Whilst increased river flows returned salinity in the Bay to within the normal oceanic range, water clarity was reduced in the western areas and Corio Bay.


The Report Card's water quality index is based on routine sampling which means the short-lived environmental and weather events that can impact water quality are not always captured. The following events occurred during the 2016–2017 reporting period:

  • During 29 December 2016, and 10 April 2017, storms brought heavy rain and flash flooding to parts of the Melbourne metropolitan region. Other significant rainfalls occurred in August, October and November 2016, and January and February 2017. All of these events had the potential to impact waterways with stormwater runoff from the hard surfaces in the city. 
  • Environmental flow releases (controlled releases of water) occurred in the Werribee, Maribyrnong and Yarra catchments. Key objectives of environmental water releases are to improve water quality, flush out sediment to improve habitat, and stimulate movement and breeding of fish by providing high water flows at the right time of the year.
  • A non-toxic algal bloom occurred from St Kilda to Brighton and in Mornington during August and September 2016. These spring blooms are common in the Bay and appeared over several weeks. In early January 2017, a potentially-toxic algal bloom occurred in Hobsons Bay. Algal blooms are not uncommon, and are most likely to occur in warm weather following stormwater run-off as river inflows introduce nutrients into the bay after heavy rain. 

Parks Victoria diver removing the highly invasive marine pest Undaria pinnatifida from a popular dive site in the Port Philip Heads Marine National Park. Source: Chris Hayward, Parks Victoria

EPA research vessel, Bar-ba-ka, in Port Phillip Bay. Source: EPA Victoria

Changes over time

The Bureau of Meteorology has identified a long-term ‘drying’ trend since the 1970s in the Melbourne metropolitan region, which shows that annual rainfall is decreasing by 50 mm every 10 years. This is one of the most significant rainfall declines across the state of Victoria.

Since 2000, there has been an overall improvement in water quality in most of the larger catchments and Port Phillip Bay.

During times of low rainfall, the state of some streams’ water quality may improve as there is little to no input from urban and rural runoff. This results in lower levels of nutrients and pollutants, and improved water clarity. However, low rainfall for some streams can reduce flows to the point where dissolved oxygen declines to levels that impact the aquatic life further downstream in the rivers. In some streams, particularly those in the north-west, salinity naturally increases during times of low rainfall because flow is more dominated by salty groundwater springs.

During times of high rainfall streams are impacted more by increased runoff, which decreases water clarity and increases nutrients and pollutants that enter waterways. The drought breaking rains in 2010 and the well above-average rainfall in 2011 resulted in overall declines in water quality, although they also brought benefits through increased stream flows and available habitat.

Average conditions between 2012 and 2014 resulted in improvements in water quality. Dry conditions returned in 2014-2015, with extremely dry conditions in 2015–2016 causing some smaller creeks to become isolated pools or drying completely, resulting in declines in the catchment WQI scores.

The return of improved stream flows due to average and above average rainfall during 2016-2017 resulted in improved water quality in most catchments, with the exception of the Yarra, which showed a slight decline in water quality due to pollution from runoff in rural areas.

While climate has shaped much of the water quality condition for the region over this period, the Dandenong and Mornington catchments have consistently shown ‘Poor’ to ‘Very Poor’ water quality. The waterways in these catchments consistently have high levels of salinity, and pollutants (metals and nutrients) and low levels of dissolved oxygen and water clarity. In these catchments, waterways tend to be small or highly modified from their natural state. Their size makes them more susceptible to the impacts of urban and industrial land use and the pollution that these types of land uses bring.

Plot of water quality index (WQI) score history for all catchments and Port Phillip Bay.


What's happened?

The Government, authorities and community have implemented a number of initiatives to improve waterway health in the Bay and catchments, including these outlined below:

  • In 2016–2017, Melbourne Water:
    • removed over 2400 m3 of debris, including litter from waterways and litter traps
    • planted almost 182 km of streamside vegetation across the region
    • controlled weeds along 1555 km of waterway
    • funded the installation of 49 km of fencing to exclude stock from entering waterways
    • improved 44 ha of aquatic habitat 
    • funded 58 projects that aim to achieve sustainable stormwater management outcomes through the Living Rivers Grants
  • The Victorian Government has prioritised the protection and improvement of Victoria's water environments. To ensure Victoria has clear and relevant standards, legal rules and statutory obligations to protect and improve the health of our water environments, the Government is reviewing two key policies: State Environment Protection Policies (SEPPs) for Waters of Victoria and Groundwaters of Victoria. The review is expected to be completed in 2018.
  • The Commissioner for Environmental Sustainability released the ‘State of the Bay 2016’ report – Victoria’s first State of the Bays report is an environmental report on the current condition of Port Phillip Bay and Western Port, displaying the physical and biological characteristics of these highly valued waterbodies and the processes that influence the environmental health of these ecosystems. The State of the Bay 2016 report was a “baseline” review and covers a more comprehensive set of the indicators of ecosystem health than the water quality subset that this Report Card covers.
  • The Department of Environment, Land, Water and Planning (DELWP) completed the draft of the ‘Port Phillip Bay Environmental Management Plan’. This plan, to be finalised in 2017, outlines a vision, objectives and actions to maintain the health and amenity of Port Phillip Bay into the future. The Plan also identifies key threats and sets targets to protect Port Phillip Bay. The Plan will help Government and other organisations work together to address the key challenges of managing Port Phillip Bay.
  • DELWP implemented Round 1 of the ‘Port Phillip Bay Fund’. Thirty six projects have received funding, for the 2017-2018 financial year, to protect the health of Port Phillip Bay (and the associated catchment areas) by reducing pollution in Port Phillip Bay, enhancing aquatic habitats, improving catchment health and increased community awareness of issues which impact the health of Port Phillip Bay.
  • The Port Phillip and Westernport Catchment Management Authority (PPWCMA), in partnership with local government, authorities, agencies and community groups, have initiated the ‘Greening the West’ initiative.
  • PPWCMA implemented the ‘Living Links’ project; an ongoing environmental and social project to create a web of green spaces in Melbourne’s south-east.
  • The $2 million 2014-2017 ‘Litter Hotspots’ grants program was introduced by EPA in 2014. This program is led by the Melbourne Waste and Resource Recovery Group, working with local councils and community groups to find local litter solutions

For more information on initiatives that are improving waterways in the Port Phillip Bay and catchments in 2016–2017, please visit Waterways Local Updates.

What's planned?

A number of priority areas and actions have been identified for Port Phillip Bay and catchments that will build on existing projects and initiatives. Priority management actions include:

  • The Environmental Management Plan for Port Phillip Bay has recently been revised. Through dedicated priority actions the revised plan aims to ensure a healthy Port Phillip Bay that is valued and cared for by all Victorians
  • Melbourne Water's Healthy Waterways Strategy, which outlines Melbourne Water's role in managing rivers, estuaries and wetlands in the Port Phillip and Western Port regions, and identifies actions planned for the future to preserve and protect waterways. During 2016-2018, Melbourne Water’s Healthy Waterways Strategy is in the process of being refreshed, with community consultation underway. This will incorporate Melbourne Water’s Stormwater Strategy from 2018-2019.
  • Melbourne Water's Stormwater Strategy, which focuses on managing stormwater to protect and improve the health of waterways and bays.
  • 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.

Program Partners

Department of Environment and Primary Industries Environmental Protection Agency Melbourne Water