See the ‘Dandenong Catchment’ page for a detailed description of the catchment.
This Report Card provides an overview of water quality in the Dandenong catchment from 1 July 2014 to 30 June 2015. The quality of the water was 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.
In 2014–15, water quality in the Dandenong catchment was ‘Very Poor.’
Summary Table: The table below shows the percentage of the Dandenong catchment that falls into each scoring category. See scoring method for more information.
Near naturally forested area at the base of Mt Dandenong
Small streams in urban and industrial areas
The routine monitoring at 17 sites gives us information for about 71 per cent of the catchment. The remaining 29 per cent of unmonitored catchment is a mix of rural and urban land use, which would typically score as ‘Very Poor’ in this region.
See the Monitoring Programs page for changes to the monitoring program.
The section 'Changes over time’ compares these annual index scores and indicators with the Dandenong catchment’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.
Water quality in the Dandenong catchment is ‘Very Poor’.
Urban and industrial land use dominates much of the Dandenong catchment. Runoff from these areas carries pollution to the waterways, which reduces waterway health. Concentrations of nutrients and metals (e.g. copper, lead, zinc, chromium) are often high due to runoff from industrial areas and roads.
Historically, many waterways in the Dandenong catchment were straightened or concrete-lined to increase their effectiveness in draining away water and reducing floods. However, this has removed natural meanders in the waterway and destroyed a lot of stream habitat, which, along with polluted run-off has decreased water quality in these waterways. For example, clearing trees around a waterway reduces shade and increases water temperature, which decreases dissolved oxygen
The exception to this ‘Very Poor’ score is the relatively undisturbed monitoring site on the edge of the forest in the upper reaches of the Dandenong catchment (see Dandenong Creek, Doongalla Forest). At this location, the WQI scores ‘Good’ because the environment is closer to its natural state. This was the only monitoring location in the Dandenong catchment with low metal concentrations, demonstrating the source of these inputs to be from industrial and urban areas within the catchment.
Despite the catchments scoring ‘Very Poor’, these waterways continue to sustain considerable populations of fish, frogs and birds. The region’s significant wetlands (Edithvale-Seaford wetlands) are recognised for their valuable diversity of waterbirds under the Ramsar Convention).
Short-term 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, river bank erosion, and wash sediments, nutrients and pollutants into waterways.
Below average rainfall was observed in 2014–15. The Bureau of Metrology (2016) noted just three days during the year when significant rainfall (between 25 – 29 mm) was recorded.
Outside of these dates, no significant environmental or weather events were recorded for the period that would have significantly affected water quality.
Looking at the scores for the Dandenong catchment going back to 2000, there is a general trend of ‘Very Poor’ water quality scores.
The water quality has most likely been influenced by urban and industrial development in the catchment over the past two decades, particularly around Hallam, Cranbourne, Lynbrook and Berwick.
Some sites have shown very slight improvements since the drought broke in 2010, but scores have remained ‘Very Poor’ due to high concentrations of metals and nutrients that originate in this catchment’s large industrial and urban areas.
Management objectives across the Dandenong catchment aim to strike a balance between managing for flood mitigation and protecting environmental values. Improvements in water quality can be difficult to achieve in catchments with heavy industrial and urban development.
Pollutants are often transported into waterways from diverse sources spread across the catchment. The implementation of projects designed to reduce stormwater inputs such as installing water-sensitive urban-designed rainwater tanks, raingardens and roadside swales (vegetated ditches designed to collect runoff) can help to improve water quality in urban waterways.
The Government, authorities and community have implemented the following initiatives to improve waterway health in the Dandenong catchments:
Environment Protection Authority Victoria (EPA)
For more information about projects and works for the Dandenong catchment in 2014–15, please see the Melbourne Water Waterways Local Updates.
A number of priority areas and actions have been identified in the Dandenong catchment 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.