See the ‘Yarra Catchment’ page for a detailed description of the catchment.
The Report Card for the Yarra catchment has generated water quality index scores for the period July 2012 to June 2013. These scores are generated using a combination of standard indicators: nutrients, water clarity (turbidity), dissolved oxygen, salinity (conductivity), pH and metals.
These are sampled monthly across 48 sites as part of catchment monitoring programs.
The following section ‘Changes over time’ compares these annual index scores and indicators with the catchment's scores from 2000.
Results can also be compared to other catchments in the section below ‘Compared to other catchments’.
Site-specific details about indicators can be found via the site lists or can be accessed directly from the map.
Summary Table: The table below shows area-weighted distribution of site scores based on subcatchments. Scores are averaged in subcatchments with multiple sites. See the scoring method for more information.
Typically forested areas in the upper catchment
Typically rural areas on the urban fringe in the mid-catchment
Mostly the Yarra River in the mid-catchment
Mostly the Yarra River in the lower urbanised catchment
Mostly small tributaries in the lower urbanised catchment
The routine monthly monitoring across 48 sites accounts for 100% of the catchment.
Overall, in the Yarra catchment 52 per cent of the waterway monitoring sites achieved a ‘Fair&lrsquo; to ‘Very Good rating’.
Most of the waterway sites that rated as ‘Good’ drain catchments that are well forested and are close to their natural state. The O'Shannassy River monitoring site located within a closed catchment was the only site that scored ‘Very Good’.
As the catchment becomes more developed toward the city, water quality scores deteriorate as waterways are increasingly impacted by human activity. Consequently, 48 per cent of the middle and lower Yarra catchment received a ‘Poor’ or ‘Very Poor’ water quality rating. The mainstream Yarra River scored ‘Good’ near Warrandyte but deteriorated on it’s course downstream and was rated ‘Poor’ at Kew.
In the lower urban parts of the catchment, the low scores are generally a result of high nutrients, such as nitrogen and phosphorus, and low water clarity, which commonly originate in the runoff from houses, industrial and commercial areas and roads. Dissolved oxygen levels were also low at times in the urban area, particularly during the summer months when flows are low and water temperature is high.
Urban waterways tend to have high metal concentrations as often the whole catchment area is urbanised. Metals are commonly found in the stormwater runoff from roads and industrial areas. Gardiners Creek is an example of an urban site with regularly high metal levels where concentrations of copper and zinc frequently exceed guideline levels. Tyre rubber is a widespread source of zinc in urban areas where it is deposited on road surfaces and then washed into waterways.
The Report Card's water quality index is based on monthly sampling which can mean short-lived environmental and weather events that can impact water quality are not always captured. This section highlights events for the 2012-13 time period.
During 2012-13 there were four separate environmental flow releases down the Yarra River from Melbourne's water storages. This contributed to both improved water quality along the Yarra River and improved waterway habitat for plants and animals.
Melbourne Water also delivered the largest environmental flow release ever for the Yarra River in May 2013. The release aimed to improve fish populations and the quality of the water by flushing fine sediment and organic material from the river bed, thereby maintaining habitat for bugs and fish life and supporting native vegetation. For further information see the Melbourne Water media release.
Generally, the Yarra catchment's water quality has improved significantly since the 1970s, and despite increased pressure from continued urbanisation and population growth it has demonstrated an overall improvement over the over the past 13 years.
This improvement is a positive measure in light of the many urban pressures the lower and middle Yarra catchments experience, which includes the landscape's growing urbanisation. Water quality has also generally improved since the drought broke in 2010.
The ‘Actions’ section below outlines projects and initiatives that will contribute toward addressing the issues outlined above.
Driven by the key water quality issues identified for the region, major projects were implemented to improve waterway health in the Yarra catchment and included the following initiatives:
For more information about projects and works in the Yarra catchment in 2012-13, please see the Waterways Local Updates.
A number of priority areas and actions have been identified in the upper, middle and lower Yarra catchments to build on existing projects and initiatives. These include:
For more information on actions planned for the Yarra catchment to improve the health of rivers and creeks, please see the Healthy Waterways Strategy.
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.