See the ‘Yarra Catchment’ page for a detailed description of the catchment.
The Report Card provides an overview of water quality in the Yarra catchment from 1 July 2013 to 30 June 2014. The quality of the water is given an overall score by combining the results of six standard water quality parameters: nutrients, water clarity (turbidity), dissolved oxygen, salinity (conductivity), pH (acidity/alkalinity) and metals.
Summary Table: The table below shows the percentage of Yarra catchment that falls into each scoring category. See 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 47 sites accounts for 100% of the catchment.
Overall, water quality in the Yarra catchment is generally ‘Fair’.
We can see a clear pattern throughout the catchment, where the water quality scores reflect the impacts of various land uses. Sites in forested parks in the upper catchment are protected from development and achieved ‘Very Good’ and ‘Good’ scores (such as O’Shannassy River).
Rural sites in the middle of the catchment typically rate as ‘Fair’. In these rural locations, nutrients and sediments are the main water pollutants. These enter waterways though runoff from farmland and when stock damage creeks and river banks.
As waters flow from the rural middle catchment and pass through more developed or urbanised areas in the lower catchment toward the city, we see a decline in water quality as waterways become increasingly impacted by human activity.
In these urban areas, ‘Poor’ to ‘Very Poor’ water quality scores generally result from a combination of factors including high nutrients, low water clarity, low dissolved oxygen (in some waterways) and high levels of metals.
High levels of nutrients, such as nitrogen and phosphorus, combined with low water clarity are caused by runoff from houses, industrial areas, commercial areas and roads. Dissolved oxygen levels can often be low during the summer months when stream flows are low and water temperatures are high.
Metals are commonly found in stormwater runoff from roads and industrial areas. Tyre rubber is a widespread source of zinc in urban areas — it collects on roads and then washes into waterways during rain events. Gardiners Creek is an example of an urban site where concentrations of copper and zinc frequently go above acceptable ANZECC guideline levels.
We know that water quality has significantly improved in the Yarra catchment since the 1970s, but what about more recently? The good news is that despite increased pressure from expanding urbanisation and a growing population, water quality has continued to improve over the past 13 years. In fact, in 2013/14, the overall Yarra catchment scores have moved up to ‘Fair’ for the first time since 2000.
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.