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.
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.
Forested upper catchments and southern area of Port Phillip Bay
Upper catchments and northern and western area including the Geelong Arm of Port Phillip Bay
Mostly the main rivers and tributaries in the rural mid-catchment areas
Mostly lower reaches of the main rivers and urban tributaries
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.
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:
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.
The Government, authorities and community have implemented a number of initiatives to improve waterway health in the Bay and catchments, including these outlined below:
For more information on initiatives that are improving waterways in the Port Phillip Bay and catchments in 2016–2017, please visit Waterways Local Updates.
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: