See the ‘Yarra Catchment’ page for a detailed description of the catchment.
This Report Card provides an overview of water quality in the Yarra catchment from 1 July 2015 to 30 June 2016. 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.
Overall, water quality in the Yarra catchment in 2015–2016 was generally ‘Poor’.
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 monitoring across 46 sites gives information about 97 per cent of the catchment. The remaining three per cent of the catchment was not included due to incomplete data because of drying waterways or unsafe site access. It is expected that the return of water to these streams will result in a slight improvement to the overall catchment rating.
See the Monitoring Programs page for changes to the monitoring program.
The section 'Changes over time’ compares this year’s annual index scores and indicators with Yarra’s scores from previous Report Cards (since 2000). Results can also be compared to other catchments.
Site-specific details about parameters can be accessed via the map.
Overall, water quality in the Yarra catchment is generally ‘Poor’.
There is 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 the O’Shannassy River).
Rural sites in the middle of the catchment are typically ‘Fair’. In these rural locations, nutrients and sediments enter waterways though runoff from farmland and when stock damage creeks and river banks. Several small tributaries in rural areas were either reduced to isolated pools or dried completely. Other locations had unsafe site access, which resulted in their exclusion from the assessment.
Water quality declines as waters flow from the rural middle catchment and pass through more developed or urbanised areas in the lower catchment.
In these urban areas ‘Very Poor’ water quality scores result from inputs of nutrients and pollutants in runoff from residential, commercial and industrial areas, roads and other hard surfaces, particularly in the smaller tributaries. Due to its size, the Yarra is somewhat protected from these impacts although at the inner suburban suburb of Kew, the Yarra River water quality was ‘Poor’ as a result of inputs from lower parts of the catchment.
Short-lived environmental and extreme weather events can impact water quality in waterways. Long-term dry spells can result in reduced river flows, increases in salinity and algal blooms, while heavy rainfalls can cause flooding and river bank erosion, and can wash sediments, nutrients and pollutants into waterways.
Below average rainfall was observed in 2015–16. The Bureau of Meteorology (2016) noted six events when significant rainfall (22–52 mm) was recorded.
Four environmental flows with a total of 8,817 million litres of water were released from storages in the catchment throughout the year. The releases aimed to improve water quality; maintain habitat for aquatic species; support native vegetation; and maintain the localised movement of native fish.
Generally, the Yarra catchment's water quality has improved since 2000 and despite increased pressure from continued urbanisation and population growth, it has demonstrated an overall improvement over the past 16 years.
This overall improvement is a positive measure in light of the many urban pressures experienced in the lower and middle Yarra catchments.
During times of low rainfall, water quality generally improved, and during years of above-average rainfalls, water quality usually declined. The most recent example of this was the drought-breaking rainfalls in 2010 and the well above-average rainfall in 2011, although the changes in overall water quality for the whole catchment were slight. Average conditions returned over the next three years, resulting in improvements to water quality up to 2013–14.
Below-average rainfalls in 2014–15 led to reduced river flows in many of the smaller tributaries entering the Yarra River. In some cases, the streams became isolated pools while others dried up completely, which resulted in a slight decline in water quality. These conditions continued into 2015–16.
Government agencies, local councils and the community have implemented the following initiatives to improve waterway health in the Yarra catchment:
Environment Protection Authority (EPA)
For more information about projects and works in the Yarra catchment in 2015–16, 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:
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.