Page 89 - VEWH Seasonal Watering Plan 2020-21
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Integrated catchment management
Altered water regimes are one of many threats to the health of Victoria’s waterways. To be effective, environmental flows need to be part of an integrated approach to catchment management. Many of the environmental objectives for water for the environment in the central region will not be fully met without simultaneously addressing issues such as barriers to fish movement, limited volumes of environmental entitlement, poor water quality, reduced contribution of groundwater to surface water flows and loss of stream bank vegetation and invasive species.
Victorian and Australian government agencies, Traditional Owner groups, community groups and private landholders collectively implement a wide range of programs that aim to protect and improve the environmental condition and function of land, soils and waterways throughout Victoria’s catchments.
Examples of complementary programs that are likely to support environmental watering outcomes in the central region include:
• Corangamite CMA’s ongoing investigations into the surface water and groundwater interactions in the Moorabool River and their continued partnership with the Batesford Quarry operators to allow water from the quarry to be discharged to the river (an important contribution to flow)
• the review of the effectiveness of recent wetting and drying regimes at Reedy Lake and recommended future directions for water management at Reedy Lake and Hospital Swamps
• Melbourne Water’s performance review and rectification works for the Dights Falls fishway on the Yarra River, which will allow native fish to move upstream under a wider range of flows
• Corangamite CMA’s scoping of channel restoration
in the upper Barwon River, investigating options to remediate constriction points along the upper Barwon River to improve environmental water deliveries from the West Barwon Reservoir
• continued works by Corangamite CMA and Melbourne Water to protect and enhance streambanks along priority reaches in the catchments including willow removal, revegetation and fencing to exclude stock
• Melbourne Water’s landscape-scale approach to improve the management of billabongs along the Yarra River to help meet cultural, ecological and liveability objectives.
For more information about integrated catchment management programs in the central region, refer to the Corangamite CMA and Melbourne Water regional catchment strategies and regional waterway strategies.
Risk management
During the development of the seasonal watering proposals for the Yarra, Tarago, Maribyrnong, Werribee, Moorabool and Barwon systems, environmental watering program partners assessed risks associated with potential environmental watering actions for 2020–21 and identified appropriate mitigating strategies. Risks and mitigating actions are continually assessed by program partners throughout the year (see subsection 1.3.6).
3.1 Central region overview
 Seasonal outlook 2020–21
Rainfall in 2019–20 was highly variable both within and between seasons across the central region’s systems. The Yarra catchment experienced above-average conditions with natural inflows achieving many planned watering actions including low flows and freshes. Lal Lal Reservoir in the Moorabool system filled in spring 2019, and
Pykes Creek Reservoir and Melton Reservoir in the Werribee system both filled and spilled. In contrast, inflows to Rosslynne Reservoir were well-below average, which meant the VEWH was unable to purchase any water to support environmental flows in the Maribyrnong system.
The Bureau of Meteorology is predicting above-average rainfall across the central region for the first three months of the 2020–21 water year, which could increase storage levels and produce some larger flow events that cannot be delivered through managed environmental flows. These conditions may allow the VEWH, Melbourne Water and Corangamite CMA to deliver watering actions that are only planned under average or wet scenarios and aim to improve rather than just maintain environmental values in the region’s waterways. This may include delivering flows over winter/spring of increased magnitude or duration, such as in the Moorabool system to provide a cue for fish (like the adult tupong) to migrate downstream to spawn.
If the central region experiences relatively dry conditions throughout 2020–21, water for the environment will mostly be used to deliver minimum low flows and freshes to maintain habitat and water quality and prevent significant decline in populations of aquatic plants and animals.
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