See the ‘Dandenong Catchment’ page for a detailed description of the catchment.
This Report Card provides us with an overview of water quality in the Dandenong catchment from 1 July 2013 to 30 June 2014. 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.
Summary Table: The table below shows the percentage of the Dandenong catchment that falls into each scoring category. See scoring method for more information.
Good quality water in parts of the upper sub-catchment improves subcatchment score above very poor
Remaining small streams in urban and industrial areas
The routine monthly monitoring at 18 monitoring sites give us information for about 76 per cent of the catchment. The remaining 24% of unmonitored catchment is mostly rural. Waterways in these rural areas typically score ‘Very Poor’ for this region.
Water quality in the Dandenong catchment is generally ‘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 industrial areas and roads.
Historically, many waterways in the Dandenong catchment were concrete-lined to increase their effectiveness in draining away water and reducing floods. However, this has destroyed a lot of natural stream habitat, which has consequently 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). There, the water quality scores ‘Good’ because the environment is closer to its natural state.
Despite the catchment 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
Looking at the scores for the Dandenong catchment going back to 2000, we see a general trend of ‘Very Poor’ water quality scores.
This trend has 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 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 urban areas.
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.