The Yarra River and Port Phillip Bay Report Card was developed to report on the water quality at sites in Port Phillip Bay and its surrounding catchments. Click on the map or list below to explore.
This Report Card provides a snapshot of water quality in Port Phillip Bay and catchments from 1 July 2014 to 30 June 2015. The quality of the water was 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.
Overall, water quality in all the river systems and the Bay has marginally declined from the previous assessment in 2013–14, except the Maribyrnong catchment where conditions were maintained. There are differences in condition between the rivers and the Bay.
Summary Table: The table below shows the percentage of the Bay and surrounding catchments that fall into each scoring category. See the scoring method for more information.
Forested upper catchments and entrance to Port Phillip Bay
Upper catchments and Port Phillip Bay
Mostly the main rivers and tributaries in the middle catchment areas on the urban fringe
Mostly lower reaches of the main rivers and urban tributaries
Mostly small urban tributaries
In 2014–15, routine monitoring occurred across 105 sites in the Bay and catchments. This represents 83 per cent of the total catchment area. The remaining 17 per cent of the catchments not monitored are mostly rural and would typically score as ‘Fair’.
The section Changes over time compares the 2014–15 Report Card scores and indicators for the catchments and the Bay to the scores from previous Report Cards (since 2000). More detail on the specific catchments and Bay is provided in their individual reports.
Site-specific details within the 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 big impact on water quality. In 2014–15 rainfall across the region was below the historic average. During winter and spring of 2014 rainfall was approximately 14 per cent and 20 per cent below the average. During summer and autumn of 2015 rainfall was approximately 7 per cent and 19 per cent below the average (Bureau of Meteorology, 2016).
These drier conditions led to significantly reduced river flow. In some cases, this resulted in no water at all, reducing some waterways to isolated pools or dry river beds, particularly in small tributaries. This generally means either there’s no water to sample or that there is a drop in water quality for some parameters. Reduced flow often results in low oxygen levels, increased salinity and algal blooms, all of which can cause stress to aquatic life. For the Werribee and Maribyrnong catchments in their “natural” state these waterways would likely dry out entirely during summer, leaving remnant chains of ponds where ground water meets the surface.
Dry conditions can also result in less stormwater runoff, leading to lower turbidity and nutrient levels in streams. A decrease in these parameters will appear as improvements to the condition of the waterway.
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 2014–15 reporting period:
These environmental flows were aimed to improve the habitat for aquatic plants, macroinvertebrates, endangered fish, frogs and platypus; and supported the successful spawning of native fish species. The environmental flows also provided water to the Yering Backswamp, a billabong adjacent to the Yarra River near Yarra Glen, which helped it to sustain its regionally important habitat.
The Bureau of Meteorology (BoM) has identified a long-term ‘drying’ trend since the 1970’s 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 in Victoria.
Since 2000, there has been an overall improvement in water quality in most of the larger catchments and the Bay. In some catchments this may be partially attributed to changes in the monitoring program.
During times of low rainfall, the condition 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 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 declines in water quality.
Average conditions over the next three years resulted in improvements in water quality up to 2013–14. In the last year, low rainfall conditions, resulted in the general drying of river catchments. Water quality in all river systems and the Bay has marginally declined, except the Maribyrnong catchment where conditions were maintained.
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 over many years. In these catchments, waterways tend to be small or highly modified from their natural state. This 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 implemented the following initiatives to improve waterway health in the Bay and catchments:
For more information on initiatives to improve our waterways in the Port Phillip Bay and catchments in 2014–15 please visit: Waterways Local Updates.
A number of priority areas and actions have been identified for the Bay and catchments that will build on existing projects and initiatives. Priority management actions include: