This Report Card provides an overview of water quality in the Dandenong 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.

In 2015–16 water quality in the Dandenong catchment was ‘Very Poor.’

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.

The routine monitoring at 16 sites give us information for about 71 per cent of the catchment. Approximately five per cent of the catchment was not included due to incomplete data, which resulted from the unsafe access to waterways in the catchment. The remaining 24 per cent of the 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’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.

What does this mean?

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 (copper, lead, zinc and 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 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.

Events

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, river bank erosion, and wash sediments, nutrients and pollutants into waterways.

Rainfall was below average in 2015–16. The Bureau of Metrology (2016) noted seven days during the year when significant rainfall (between 20–42 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.

Bar chart of WQI and indicator scores for Dandenong Catchment.

Hendersons Creek, Upper Dandenong. Source: Melbourne Water

Dandenong. Source: Melbourne Water

Changes over time

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. The assessment of water quality in 2015–16 is essentially unchanged from the water quality results of 2014–15.

Plot of WQI history for Dandenong Catchment

Actions

What's happened?

The Government, authorities and community have implemented the following initiatives to improve waterway health in the Dandenong catchments:

Melbourne Water

• Planted 28 km of native vegetation; maintained 152 km of native vegetation; and installed 0.4 km of stock-exclusion fencing.
• Removed 122 cubic metres of silt and sediment; and removed 550 cubic metres of litter and debris from waterways that were affecting basins in the Dandenong catchment.
• As part of the Enhancing Our Dandenong Creek project, Melbourne Water designed and constructed six habitat sites for threatened Dwarf Galaxias.
• Conducted monitoring, mapping and source tracking of key pollution hot-spots in the Dandenong Creek catchment.
• Partnered with local communities to construct water-sensitive urban designed raingardens and bioswales (vegetated ditches designed to collect runoff) to capture stormwater for treatment and reuse.
• Worked with the local council to upgrade and improve streamside habitat and control erosion in the Dandenong catchment.
• Stabilised 300 metres of Mile Creek to prevent future erosion around the waterway.
• Developed a pilot program in Belgrave to help reduce threats to local platypus populations by working with community groups to raise awareness of platypus in Monbulk Creek.
• Undertook fortnightly blue-green algae monitoring during the summer period at nine sites.
• Undertook weekly monitoring at five sites to better understand recreational health risks and help identify any pollution sources during the summer period.

Environment Protection Authority Victoria (EPA)

• The $2 million 2014-2017 Litter Hotspots grants program was introduced by EPA in 2014. This program is led by the Melbourne Waste and Resource Recovery Group, working with local councils and community groups to find local litter solutions.
• Conducted Hot Spot investigations in Old Joes Creek and Bungalook Creek.

For more information about projects and works for the Dandenong catchment in 2015–16, please see the Melbourne Water 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:

• Melbourne Water and EPA are working in partnership to improve the health of Dandenong Creek through a five-year program consisting of four different projects known as 'Enhancing our Dandenong Creek’ (EODC).
• Melbourne Water is implementing their ‘Healthy Waterways Strategy’ and ‘Stormwater Strategy’. These strategies cover the five years from 2013–14 to 2017–18 and contain information about planned actions to improve the health of rivers and creeks in the Dandenong catchment.
• Modelling of water flow in the Dandenong Creek catchment has been developed to provide a better understanding of the interactions of groundwater and surface water flows and to assess potential climate change scenarios.
• Improving streamside and wetland vegetation across the catchment, including within the Ramsar-listed Edithvale-Seaford Wetlands.
• Continuing EPA and Melbourne Water attendance at pollution events across the catchment.
• Roll out of the Litter Hotspots grants program.