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.
Click on a site to see further information.
See ‘Western Port and Catchment’ page for a detailed description of the bay and catchment.
This is the first Water Quality Report Card for Western Port and its associated catchment. It provides a snapshot of water quality 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.
In 2016–2017, water quality in Western Port was ‘Very Good’ and its catchment’s water quality was ‘Poor’.
Summary Table: The table below shows the percentage of Western Port and surrounding catchment that fall into each scoring category. See the scoring method for more information.
Western arm of Western Port
Tributaries in the upper catchment
Eastern arm of Western Port and the Bunyip and Lang Lang Rivers in the mid and upper northern catchment
Small creeks in the North, on the Mornington Peninsula and the mid Bass catchment
Watsons Creek, Wylies Drain in the north and the lower Bass River
In 2016–2017, routine monitoring occurred across 35 sites in catchments of Western Port, with 2 of these sites located within the bay itself. This represents 61 per cent of the total catchment area. The remaining 39 per cent of the catchments, which are not monitored, are mostly rural and would typically score as ‘Poor’.
The section Changes over time compares the 2016–2017 Report Card scores and indicators for Western Port and catchment to previous annual Water Quality Index (WQI) scores generated since 2000. More detail on Western Port and its catchment is provided in their individual reports.
Site-specific details within Western Port and its catchment can also be accessed directly from the map or within the individual catchment and Western Port reports.
See the Water Quality Index section for information on general water quality trends and sources of pollution.
Annual and seasonal variability in rainfall, temperature and solar exposure (how sunny it is) can impact on water quality in Western Port and catchment waterways.
Rainfall mostly impacts on water quality in waterways. High rainfall events can increase the amount of runoff, carrying sediments, nutrients and pollution into waterways, which reduces water quality. Low rainfall can result in low dissolved oxygen levels and increased salinity, which also results in reduced water quality. In 2016–2017, rainfall across the region was near average in the northern catchments of Western Port and slightly below average in the eastern catchment.
While annual rainfall was near average, monthly rainfalls exceeded long term averages in October 2016, from January to April 2017 and in June 2017. Regular high-rainfall events (greater than 20 millimetres) also occurred across the catchment, resulting in slight declines in water quality in tributaries in the northern catchment of Western Port, as was observed in the Cardinia Creek at Upper Beaconsfield site. This was associated with runoff to tributaries in rural and natural areas of the upper catchment. These small waterways tended to show higher levels of sediment and nutrients because the effects of runoff are more concentrated over a small area.
In Western Port, water quality can be impacted by waterway discharges from the surrounding catchment, particularly in areas close to river mouths and discharge points. Waterway discharges were close to average for the Lang Lang and Bass rivers while the Bunyip River was above average. Low stream-discharge into Western Port reduces the input of sediments, nutrients and pollutants. However, reduced discharge can lead to increased salinity, particularly in summer.
During summer, when temperatures are warmer and solar exposure is high, salinity in the shallow north-eastern mudflats region can exceed the normal oceanic range as a result of evaporation. In 2016-2017, summer temperatures were close to average and solar exposure was slightly below average; combining these climatic variables with above average rainfall in the catchment over summer counteracted the effects of evaporation, maintaining salinity levels within the normal oceanic range.
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:
Since 2000, water quality in Western Port has generally been ‘Good’ to ‘Very Good’ and water quality for the catchment has consistently been ‘Poor’.
During times of low rainfall, the water quality of some streams may improve as there is little to no input from 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. Low stream-discharge into Western Port can also reduce the input of nutrients and pollutants. However, reduced freshwater inflows can lead to increased salinity above the normal oceanic range, particularly during summer when evaporation rates can exceed catchment inflows.
During times of high rainfall, the catchment streams are impacted by increased runoff, which decreases water clarity and increases levels of nutrients and pollutants that enter waterways. This results in high stream-discharges being delivered into Western Port, which increases levels of catchment derived sediments and pollutants in the bay and potentially encourages algal growth due to increased nutrient availability. At these times, low water clarity decreases the availability of sunlight, necessary for photosynthesis, and limits algal growth. Algal blooms are not common in Western Port due to the strong tidal exchange with Bass Strait. Large freshwater inputs also lead to low levels of salinity, below the normal oceanic range, as occurred during winter and spring from 2010-2014.
Gradual water quality improvement in the catchment waterways have occurred since the drought-breaking rains arrived in 2010. The overall water quality in Western Port has fluctuated due to variable river discharge volumes altering salinity and algae levels. Sediment and nutrient inputs to Western Port are also dependant on discharge volume. Additional to catchment derived sediment and nutrient inputs to Western Port, internal processes also contribute to decreased water clarity and increased nutrient levels, further reducing water quality; these include the erosion of the eastern mud cliffs by wind generated waves, and the resuspension of sediments and nutrients from tidal movement and wind generated waves in the north-eastern mudflats region.
Due to a small number of monitoring events in Western Port, no WQI scores were calculated from 2005-2008. See the Monitoring Programs page for more details about the monitoring program.
The Government, authorities and community have implemented a number of initiatives to improve waterway health in Western Port and catchment, including these outlined below:
For more information about projects and works in the Western Port catchment in 2016–2017, please see the Waterways Local Updates.What's planned?
A number of priority areas and actions have been identified for Western Port and catchment that will build on existing projects and initiatives. Priority management actions include: