See the ‘Maribyrnong Catchment’ page for a detailed description of the catchment.
This Report Card provides an overview of water quality in the Maribyrnong 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 Maribyrnong catchment was ‘Fair’.
Summary Table: the table below shows the percentage of the Maribyrnong catchment that falls into each scoring category. See scoring method for more information.
The Maribrynong River, Riddells Creek, the upper Deep Creek and the mid-Jacksons Creek, tributaries of the mid-catchment
Lower Jacksons Creek and Deep Creek
Densely populated urban and industrial tributaries in the lower catchment
The routine monitoring across 15 sites gives information for about 77 per cent of the catchment. Approximately two per cent of the catchment was not included due to incomplete data, which resulted from the drying of waterways in the catchment and unsafe access to waterways. The remaining 21 per cent of unmonitored catchment is mostly rural, which would typically score as ‘Fair’ for this region.
See the Monitoring Programs page for changes to the monitoring program.
The section 'Changes over time’ compares this year’s annual index scores and indicators with the Maribyrnong’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.
The water quality in the Maribyrnong catchment is ‘Fair’. There is a clear pattern throughout the Maribyrnong catchment, with the water quality scores reflecting the impacts of climate and various land uses.
The Maribyrnong catchment experienced exceptionally low rainfall over spring 2015, and late summer to early autumn 2016. This led to the drying of smaller streams and an increase in salinity, as a result of saline groundwater entering the waterways due to lower river water levels. Barringo Creek in the upper catchment, which historically has ‘Good’ to ’Very Good’ water quality, also dried up completely. It is expected that the return of water to these streams will result in an overall improvement in the catchment’s water quality rating.
Streams in the upper catchment, such as Jacksons Creek, have little impact from urbanisation and industry, resulting in ‘Good’ water quality. The majority of the mid to upper catchment is primarily used for agriculture. Runoff from agricultural land can be a major source of sediment and nutrients in rural waterways, which lowers water quality. Reduced rainfall over the last two years has resulted in less evidence of these types of impacts.
Only 10 per cent of the land in the Maribyrnong catchment has been urbanised, which means that the overall water quality is generally better than in other more urbanised catchments. However, waterways in the lower catchment urban areas are experiencing the effects of pollution and stormwater associated with residential and industrial development. This is why water quality in highly-urbanised regions of the catchment rated ‘Very Poor’.
Smaller waterways flowing into the Maribyrnong River tended to show high levels of nutrients and metals and low water clarity. This is primarily because they are small and the effects of pollution are more intense when there’s not much water to dilute it.
Short-lived environmental and extreme weather events can impact water quality. Long-term dry spells can result in reduced river flows, increases in salinity levels and algal blooms, whilst heavy rainfalls can cause flooding and river bank erosion, and wash sediments, nutrients and pollutants into waterways.
Below average rainfall was observed in 2015–16. The Bureau of Meteorology (2016) noted just three days during the year when significant rainfall (between 20–35 mm) was recorded.
Several environmental flows (controlled releases of water) were delivered to waterways in the Maribrynong catchment. Two environmental flows with a total of 300 million litres of water were released from Rosslynne Reservoir into the lower Jacksons Creek to improve water quality, provide habitat for fish and water bugs and benefit streamside vegetation. Jackson’s Creek is a priority area because of its value to the community and the platypus population it supports. Another release was delivered to Deep Creek, which aimed to revitalise the creek environment and raise water levels to protect the habitat of the vulnerable Yarra Pygmy Perch.
Looking at the water quality scores for the Maribyrnong catchment going back to 2000, there is a trend of an overall improvement in water quality. During this time, water quality can be attributed to both climate and human activities.
During times of low rainfall, stream conditions may appear to be good as there are little or no inputs from runoff, resulting in lower levels of nutrients and pollutants and improved water clarity. However, reduced water levels and dissolved oxygen levels, at these times can decrease overall water quality and stream health.
During times of high rainfall and increased runoff, there is a decrease in water clarity and an increase in nutrients and pollutants, resulting in poor water quality. The drought breaking rains in 2010 and the above-average rainfall in 2011 resulted in declines in water quality. Water quality gradually improved with average climatic conditions until 2014–15, when dry conditions returned.
The extreme dry conditions observed over this year have resulted in a decline in the catchment WQI score compared to the previous assessment in 2014–15. Declines in water quality occurred at the sub-catchment level in Jacksons Creek and the Maribyrnong River upstream of the urban fringe, as well as in the upper catchment of Riddells Creek.
The Government, authorities and community have implemented the following initiatives to improve waterway health in the Maribyrnong catchments:
Environment Protection Authority (EPA)
For more information about projects and works in the Maribyrnong catchment in 2015–16, please see the Waterways Local Updates.
A number of priority areas and actions have been identified in the Maribyrnong catchment to build on existing projects and initiatives. These include:
The following figures show a comparison of scores for each identified water quality indicator in the catchments and Port Phillip Bay.