Page 203 - VEWH Seasonal Watering Plan 2020-21
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Table 5.2.1 Potential environmental watering actions and objectives for the Barmah Forest (continued)
5.2 Victorian Murray system
    Potential environmental watering action
Functional watering objectives
        Autumn/winter low flow in the Murray River (1,800– 4,000 ML/day downstream of Yarrawonga during May to June)
Scenario planning
Table 5.2.2 outlines the potential environmental watering and expected water use under a range of planning scenarios.
The ecological objectives at Barmah-Millewa Forest require sustained flows in the Murray River that peak in spring. Flow control structures are used to direct water from the Murray River channel into the forest and facilitate the later return of most of that water back to the river for use further downstream.
Demands for water for the environment in Barmah Forest vary significantly in response to natural conditions. Variable winter/spring low flow and spring/summer freshes are required under all scenarios. The variable winter/spring low flow is required to maintain habitat and movement opportunities for aquatic animals (such as native fish) and is achieved by keeping the regulating structures open and allowing water to move in and out of the forest in response to normal flow changes in the Murray River. The spring/ summer freshes are achieved by providing changes in the flow rate in the Murray River below Yarrawonga Weir.
Under drought and dry conditions, potential environmental watering actions will primarily aim to maintain water levels and water quality in refuge habitats to sustain fish and turtle populations. Actions to achieve these objectives require relatively small volumes of water to be directed into the forest. These actions are unlikely to return much water to the Murray River for downstream use.
Under the average or wet scenarios, the focus shifts to building resilience in the system by increasing the ecological response to natural flood events. Specific actions under
the average or wet scenarios may include extending the duration of natural flooding to increase the germination
of wetland plants (such as Moira grass) in floodplain marshes or extending watering in river red gum forests
to maintain the health of the trees. These actions require large volumes of water to be directed into the forest, with environmental water provided as a directed release from Hume Reservoir and managed via forest regulators. Most
of the water used for these actions is eventually returned
to the Murray River through the natural shedding action
of the floodplain. Targeted wetland watering may occur under various scenarios to support the breeding of colonial nesting waterbirds and other flood-dependent birds via the diversion of water through specific regulators.
Spring wetting of floodplain marshes is not considered
a high priority in 2020–21 under the dry and drought scenarios, but it would provide environmental benefit
and may be delivered under certain circumstances. For example, if above-channel-capacity operational transfers from Hume Reservoir are delivered through Barmah Forest, then the watering action could be achieved by delivering a relatively small volume of environmental flow on top of or following the operational delivery. A multi-site environmental watering objective supporting whole-of-River-Murray and/ or downstream environmental objectives during winter and spring may also deliver flows through Barmah Forest, and these could be supplemented to optimise environmental outcomes in Barmah Forest. The volume of water for the environment required to achieve the floodplain marsh flow objectives under the dry or drought scenarios depends on demands for operational water or environmental multi-site events, and it is therefore not estimated in Table 5.2.2 below.
  Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21 | 201
Environmental objectives
 Spring wetting of floodplain marshes (variable flow rates of 9,500–18,000 ML/day below Yarrawonga Weir
for three months during September to December)
• Wet open plains for sufficient duration to allow the growth of floodplain marsh vegetation
• Provide water to forest wetlands and low-lying floodplain areas to create foraging opportunities for waterbirds and increase available habitat for turtles, frogs and small-bodied native fish
             • Increase water depth in the Murray River channel to provide habitat for large-bodied native fish in the Murray River and unregulated anabranches in Barmah–Millewa Forest

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