See the ‘Werribee Catchment’ page for a detailed description of the catchment.
This Report Card provides an overview of water quality in Werribee 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 Werribee catchment that falls into each scoring category. See scoring method for more information.
Forested upper catchment
Rural areas in the upper and mid-catchment
Urban areas in the lower catchment
Mostly industrial areas in the lower catchment
The routine monthly monitoring across 15 sites accounts for 73% of the catchment. The remaining 27% of unmonitored catchment is mostly rural which typically scores as Fair for this region.
Overall water quality in the Werribee catchment is generally ‘Fair’.
We can see a clear pattern throughout the catchment, where the water quality scores reflect the impacts of various land uses.
The site in the upper Lerderderg River) is protected from development and had a ‘Good’ score, continuing the result from previous years for sites in this region. Sites in the lower catchment consistently scored very poorly (such as Kororoit Creek). The exception was the Werribee River at Riversdale Road that contained “Good” quality water at the urban growth boundary.
Rural sites in the upper and middle catchment typically score as ‘Very Poor’ to ‘Fair’. In these rural locations, nutrient runoff is the main water pollutant, which generally ends up in the waterways through runoff from farmland, through livestock damaging creeks and river banks, and through discharges from septic tanks.
As waterways of the Werribee catchment flow into more populated and industrial regions of the lower catchment, water quality declines, which is largely due to sediment and other pollutants (such as metals) entering waterways through runoff from roads, industrial, and agriculture areas.
Looking at the scores for the Werribee going back to 2000, we see a trend of improvement in water quality. Changes in water quality over time can often be attributed to both weather and human activities.
When the drought broke in 2010, water quality improved in the Werribee River due to increased rainwater flows in waterways throughout the catchment. Increased flows decrease salinity and improve dissolved oxygen by creating turbulence (click on the monitoring sites along the Werribee River to see good examples of this). In contrast, the levels of metals found in the region’s smaller waterways such as Cherry, Skeleton and Kororoit Creeks are, on average, consistently ‘Very Poor’. This is likely to be caused by historical and ongoing industrial activity and related runoff.
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.