Page 105 - VEWH Seasonal Watering Plan 2020-21
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System overview
The Maribyrnong catchment is located to the north-west of Melbourne. The main waterways in the catchment are Jacksons Creek, which flows south-east from Mount Macedon, and Deep Creek, which flows south from Lancefield. These two tributaries join at Keilor North to form the Maribyrnong River, which flows south to join the Yarra River at Yarraville, before flowing into Port Phillip Bay.
Rosslynne Reservoir is in the upper reaches of Jacksons Creek near Gisborne, and it is the only major storage in the Maribyrnong catchment. The reservoir has a release capacity of 20 ML per day, which significantly constrains the environmental outcomes that can be achieved in the Maribyrnong system. Water for the environment is primarily used to support environmental outcomes in Jacksons Creek between Rosslynne Reservoir and the confluence with Deep Creek (that is, environmental flow reaches 6 and 7 shown in Figure 3.4.1). These two reaches are described as upper and lower Jacksons Creek respectively.
The VEWH does not hold an environmental entitlement in the Maribyrnong system, and it relies on opportunistic, temporary trade to meet demands. Melbourne Water and the VEWH work with local diversion licence holders to purchase unused water when it is available to support environmental outcomes. This arrangement is negotiated each year, and it only occurs with the agreement of all parties involved.
Environmental values
The upper Maribyrnong catchment contains areas of intact streamside vegetation, which provide important habitat for native fish including migratory short-finned eels, common and ornate galaxias, flathead gudgeon, tupong and Australian smelt. A large population of waterbugs provides abundant food for a significant platypus population in several reaches in the Maribyrnong system.
Environmental watering objectives in the Maribyrnong system
3.4 Maribyrnong system
     Protect and increase populations of native small- bodied fish
  Maintain channel morphology
     Maintain platypus population
   Maintain and improve the condition, abundance, diversity and structure of instream and streamside vegetation
    Support a wide range and high biomass of waterbugs, to break down dead organic matter and support the river’s food chain
    Maintain water quality, particularly oxygen concentrations
Traditional Owner cultural values and uses
Melbourne Water has made initial contact with Boon Wurrung Foundation, Bunurong Land Council Aboriginal Corporation and Wurundjeri Woi Wurrung Cultural Heritage Aboriginal Corporation, to discuss environmental watering in the Maribyrnong system.
Social, recreational and economic values and uses
In planning the potential watering actions in Table 3.4.1, Melbourne Water considered how environmental flows could support social values (such as community connection and amenity). This includes repeating the outcomes of watering in 2019–20, where releases into the upper reaches of the Maribyrnong helped maintain healthy habitat and improve water quality.
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