See the ‘Dandenong Catchment’ page for a detailed description of the catchment.
The Report Card for the Dandenong 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.
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’.
Summary Table: The table below shows area-weighted distribution of site scores based on subcatchments. Scores are averaged in subcatchments with mutliple sites. See scoring method for more information.
At the base of Mt Dandenong
Small streams in urban and industrial areas
The routine monthly monitoring across 18 sites accounts for 76% of the catchment. The remaining 24% of unmonitored catchment is urban which typically scores as Very Poor for this region.
With the exception of a relatively undisturbed monitoring site on the edge of the forest in the upper reaches of the Dandenong catchment (see Dandenong Creek, Doonalla Forest), the water quality scores in this catchment are usually Very Poor.
Urban and industrial land use dominates much of the Dandenong catchment. Runoff from these areas carries pollution to the waterways, which degrades waterway health. Concentrations of nutrients and metals (copper, lead, zinc, chromium) are often high due to runoff from roads and industrial areas.
Historically, many waterways in the Dandenong catchment were concrete-lined to render them more effective in draining water and reducing floods. However, this has destroyed a lot of natural habitat which consequently impacted water quality. For example, clearing trees around a waterway reduces shading and increases water temperature.
Despite the creeks scoring generally Poor to Very Poor water quality, the dissolved oxygen concentrations were generally rated as Fair. These waterways continue to sustain considerable populations of fish, frogs and birds and the catchment's significant wetlands (Edithvale-Seaford wetlands) are recognised for their valuable diversity of waterbirds under the Ramsar Convention.
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 reporting period.
There were no significant environmental or weather events recorded for the period in this catchment that would have significantly affected water quality.
There has been a significant amount of urban development in the catchment over the past two decades, particularly around Hallam, Cranbourne, Lynbrook and Berwick. As a result, overall water quality in the Dandenong catchment has remained Very Poor over the past 13 years.
Some sites have demonstrated improvements since the drought broke in 2010 but scores have remained Poor to Very Poor due to high concentrations of metals and nutrients that originate in this catchment's large industrial and urbanised areas.
The ‘Actions’ section below outlines projects and initiatives that will contribute toward addressing the issues outlined above.
Management objectives across the Dandenong catchment need to strike a balance between managing for flood protection and environmental values, because the catchment provides habitat for some protected plants and animals.
Improvements in water quality can be difficult to achieve in catchments with heavy urban land use. Pollutants are often transported into waterways via stormwater from sources that are spread across the catchment. The initiation of actions to reduce stormwater such as installing rainwater tanks, raingardens and roadside swales can help to improve water quality in urban areas.
Driven by the key water quality issues identified for the region, major projects were implemented to improve waterway health in the Dandenong catchment and included the following initiatives:
For more information about projects and works for the Dandenong catchment in 2012-13, please see the 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:
For more information about actions to improve the health of rivers and creeks planned for the Dandenong catchment, 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.