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Dandenong Catchment

Land Use

Urban

Rural

Forest

Water Quality Index

Very Good

Good

Fair

Poor

Very Poor

See the ‘Dandenong Catchment’ page for a detailed description of the catchment.

Report Card for July 2012 – June 2013

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.

These are sampled monthly across 18 sites as part of the 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’.

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.

Area Score
0%

Very Good
Near-natural high quality waterways

2%

Good
Meets Victorian water quality standards

At the base of Mt Dandenong

0%

Fair
Some evidence of stress

5%

Poor
Under considerable stress

Kananook Creek

93%

Very Poor
Under severe stress

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.

What does this mean?

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.

Events

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.

Bar chart showing WQI and indicator scores for Dandenong Catchment Bar chart showing WQI and indicator scores for Dandenong Catchment

 

dandenong-hendersonsckupperdandenong.jpg Hendersons Creek, Upper Dandenong. Source: Melbourne Water

MelbourneWater.jpg Dandenong. Source: Melbourne Water

Changes over time

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.

Diagram of WQI history for Dandenong Catchment Diagram of WQI history for Dandenong Catchment

Actions

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.

What's happened?

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:

  • The construction of the largest stormwater treatment wetland in the southern hemisphere: The Dandenong Valley Wetland is one of 50 wetlands built over the past decade as part of a $60 million program aimed at improving the health of rivers, creeks and Port Phillip Bay by reducing pollution including nitrogen. The Dandenong Valley Wetland protects Dandenong Creek and Port Phillip Bay through trapping about 5,000 tonnes of suspended soils, 9 tonnes of phosphorus and 28 tonnes of nitrogen every year.
  • EPA and Melbourne Water initiated investigations to identify possible causes and response actions for the long-term poor water quality in Dandenong Creek. This effort identified high levels of metals in the water as well as high metals, insecticides and fungicides in the sediments of Dandenong Creek and its tributaries. EPA is working with industrial businesses in the catchment to improve business practices and to reduce pollutants being discharged to the creek.
  • An EPA hotspot investigation at Old Joes Creek in the Upper Dandenong Creek, that resulted in consequent remedial action on local businesses.
  • Partnership projects with local councils to build wetlands, raingardens and swales to treat stormwater runoff and remove pollutants that would otherwise end up in waterways.
  • Established the Dobsons Creek Tanks for Helping Your Creek program in partnership with South East Water and Knox Council to install rainwater tanks that will reduce stormwater runoff into Dobsons Creek.
  • Melbourne Water planting of 13 km native vegetation and removal of weeds from 77 km of waterways in the Dandenong catchment.

For more information about projects and works for the Dandenong catchment in 2012-13, please see the Waterways Local Updates.

What's planned

A number of priority areas and actions have been identified in the Dandenong catchment to build on existing projects and initiatives. These include:

  • Improving streamside and wetland vegetation across the catchment, including within the Ramsar-listed Edithvale-Seaford Wetlands.
  • Focusing on developing recreation and amenity areas around popular waterways for the community.
  • Updated guidance for onsite wastewater management to reduce the impacts of stormwater pollutants and flows.
  • An EPA hotspot investigation of Eumemmerring Creek.

For more information about actions to improve the health of rivers and creeks planned for the Dandenong catchment, please see the Healthy Waterways Strategy.

Compare to other Catchments

The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.

Diagram of nutrient score history for catchments and bay

Diagram of oxygen score history for catchments and bay

Diagram of water clarity score history for catchments and bay

Diagram of salinity score history for catchments and bay

Diagram of score history for catchments and bay

Diagram of metals score history for catchments and bay

Program Partners

Department of Environment and Primary Industries Environmental Protection Agency Melbourne Water