Yarra River
Coordinator: Graham Rooney,
Melbourne Water
Introducing the Yarra River Catchment
 The
Yarra River Catchment in Victoria is one of the
CRC’s five focus catchments.
The information given below is intended to give
readers a feel for the physical nature of the
catchment, the key issues facing catchment managers
in the region, and key stakeholder groups involved
in catchment management and waterway-related research.
About Melbourne Water
People often ask me why Melbourne Water is associated with the CRC for Catchment Hydrology, so I think it is appropriate to start at this question and explain our interest.
Melbourne Water comprises 450 people who manage sewerage, drinking water supply and drainage functions. I am part of the drainage function (Waterways and Drainage Group) where we provide everything from stormwater run-off requirements and advice on new subdivisions, through to controlling pest animal and plant species along waterways, and improving stormwater quality. The Group spends about $6 million to $8 million annually on waterway ‘rehabilitation works’. Our jurisdiction covers a majority of the Port Phillip and Western Port catchments, and managed assets include waterways, channels, underground drains, retarding basins, pumping stations, levee banks, tidal gates, and wetland systems.
Then there is the Water Group, which harvests ‘wholesale’ drinking water, and sells it to the ‘retail’ water utilities. The Water Group needs information on factors affecting the yield of water supplied from catchments to reservoirs, and the means of managing water quality within reservoirs. Hence our involvement and great interest with the CRC.
About the Yarra River catchment
The Yarra River rises in the Great Dividing Range to the east of Warburton and
flows 245 kilometres in a west to southwesterly
direction until entering Port Phillip Bay at Newport.
Its catchment area is greater than 4,000 square
kilometres and 1.5 million people live within its
boundaries. Lower reaches flow through urbanised
country, but a majority of the river is in a rural
catchment.
Records over the period 1891 to 1986 have given a mean annual flow in the Yarra River (Warrandyte) at 718,000 ML (an average of 1,967 ML/day). The highest flow recorded at the city end is 1,120 cumec in 1934 (96,770 ML/day), while the lowest flow recorded is 0.2 cumec in 1968 (17 ML/day).
Unfortunately, the Yarra River has been always known as turbid – with a reputation for the river that ‘flows upside-down’. This is partly unfair, since the river is turbid by nature, picking up clay particles as it flows through an area of unstable soils in the upper Yarra Valley. Admittedly, land-use changes do exacerbate turbidity levels.
Current Yarra catchment management issues
- There has been extensive clearing through a majority of the catchment, along with the traditional conversion to agricultural land uses. A simple loss of the pre-existing tree and shrub cover is sufficient alone to affect the river detrimentally. Riparian vegetation is either poor or non-existent along many reaches. Weed invasion is rife.
- There is increasing pressure on river flows from diversions and off-stream storage – with 1,319 licences and an allowed annual volume of 34,770 ML to be taken from the river. Water is also diverted into Sugarloaf reservoir from the Yering Gorge site – for supply of treated drinking water.
- Melbourne is rapidly spreading, and we want to at least maintain water quality in our streams. In 1990, all urban areas accounted for 1,500 square kilometres, and it is estimated this will grow to 3,100 square kilometres by 2020. We need information and tools on how best to maintain water quality – in both ‘green-field’ developments, and new urban ‘in-fill’ developments.
- Loss of in-stream habitat is regarded as a serious problem. Some 40% of waterways are rated as ‘poor’ or ‘very poor’ in terms of habitat structure.
- Port Phillip is nitrogen limited, and catchment load reductions have been recommended in order to protect the bay’s ecosystem into the future. Storm events have been identified as the key to managing nitrogen-load reductions.
- Historical willow planting along many reaches is evident today in the proliferation of mature stands. Biodiversity and channel capacity suffers, but fortunately, we know what needs to be done to rehabilitate streams from the willow menace. All we need is time and money.
- Fish navigation appears possible - even through urban inner Melbourne - however so many barriers remain. Native fish struggle with fishway designs that work overseas, so information is needed on cost-effective designs that will work in our country and jurisdiction.
- Bacterial contamination at bay beaches is a perennial public concern, and stormwater runoff is seen as a major culprit.
- Litter in streams and on bay beaches is regarded as a serious water quality issue by the public.
If in-stream ecosystem values are to be improved, we need information on the nature of land-based works, and where they should be concentrated. So many of the CRC projects will directly link with Waterways and Drainage programs. The Water Group has benefited from the initial CRC research, in both understanding catchment-vegetation influences on water yield to reservoirs, and the nature of diffuse-source contributions to poor reservoir water quality. We expect these understandings to grow, while being complemented with information for better managing in-stream flows
Our main pursuits and philosophy
- Poor water quality is a concern, and diffuse sources have to be managed if improvements are to occur.
- We consider that improving stream health - including fish, invertebrates, and platypus – is the ultimate measure of whether waterway management programs are working.
- Waterways and Drainage is moving towards revegetation from a previous emphasis on bed and bank stabilisation – in particular, there is a focus on riparian zone rehabilitation that incorporates ‘indigenous’ broad vegetation types.
- Programs are being developed in order to scope
the reduction of nitrogen loads to Port Phillip
Bay, and it is essential to work with other
agencies if possibilities are to be achieved.
- We are encouraging the construction of wetland systems to treat urban stormwater.
- There is a greater interest in establishing if and how our waterway works affect specific animal and plant communities, and if so, how may we improve our works
Possibilities and synergies
Melbourne Water is a participant in the CRC for Freshwater Ecology, so there are wonderful opportunities in undertaking joint research. Because we undertake a large number of capital works projects each year, it is possible to schedule research on relevant projects.
A Yarra Forum is being initiated, where researchers and managers can come together to reveal findings and gaps in our knowledge.
A number of ‘friends’ groups exist in the catchment. All are enthusiastic, and along with Waterwatch groups, want to provide assistance.
Waterways and Drainage is not the only body managing the drainage system. Municipal government manages the smaller systems that feed into ours. Links already exist to several municipalities due to Waterway Activity Plans and Stormwater Management Plans. These links may prove useful in the new CRC.
As Focus Catchment Coordinator, I will be preparing a regular newsletter containing information on CRC projects and other studies and research of interest in the Yarra basin. If you would like to receive copies of the newsletter, send me an e-mail.
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