Page 220 - VEWH Seasonal Watering Plan 2020-21
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 5.2 Victorian Murray system
Table 5.2.8 Potential environmental watering actions and objectives for the central Murray wetlands (continued)
      Potential environmental watering action
Guttrum Forest (partial fill in winter 2020, with top-ups in spring/summer if required to support waterbird breeding)
Richardsons Lagoon (fill in winter/spring, top up as required)
Guttrum Forest (partial fill in autumn/winter 2021)
Scenario planning
Table 5.2.9 outlines the potential environmental watering and expected water use under a range of planning scenarios.
There are seven high-priority (tier 1) wetlands that are planned to receive environmental water releases under all scenarios during 2020–21. Watering at four of these wetlands aims to maintain critical habitat for rare or threatened species: Round Lake (Murray hardyhead),
Lake Elizabeth (Murray hardyhead), Third Reedy Lake (southern purple spotted gudgeon) and Wirra-Lo wetland complex (growling grass frog). Watering at McDonalds Swamp, Hird Swamp and Guttrum Forest is needed to support North Central CMA’s strategy of providing a mosaic of wetland habitat types and ecosystem services across the central Murray region over multiple years. The planned watering actions at these seven sites are expected to
use between 17,700 ML and 18,300 ML, depending on weather conditions. Watering at Richardson’s Lagoon is also a high priority under the average and wet scenarios, as water availability will allow the optimum watering regime to be met.
The environmental values at Richardsons Lagoon will benefit from watering in winter/spring 2020, but it is considered a lower priority as its minimum watering regime will allow for the site to remain dry between events for up to two years.
A flow through Hird Swamp from Pyramid Creek has been identified as a tier 2 watering action under all scenarios, but it may be elevated to a high-priority action if a spring high flow occurs in Pyramid Creek when Hird Swamp is
Functional watering objectives
• Wet existing adult river red gums to support growth and drown river red gum saplings to maintain open-water habitat
• Promote the growth and re-establishment of aquatic and tall marsh vegetation
• Maintain depth of wetland to support frogs and waterbird feeding and breeding
• Promote the growth of aquatic macrophytes, reeds and rushes, which in turn would support aquatic biota
• Wet the higher floodplain environment to maintain eucalypt floodplain woodland and create habitats for waterbirds, reptiles and frogs and associated wetland animals to feed and breed
• Increase food resources (e.g. waterbugs and zooplankton) for waterbirds and other wetland animals
• Increase water depth and extent to trigger wetland plants to germinate in late winter and early spring
• Provide feeding and refuge habitat for waterbirds and frogs
Environmental objectives
                                   already full. This is very similar to the flow delivered through Johnson Swamp in 2019–20, and it would enhance the environmental benefit of the planned winter/spring fill at
Hird Swamp by transporting carbon and waterbugs from the wetland to Pyramid Creek, where it can increase food for native fish. Potential watering actions for Pyramid Creek in 2020–21 are described in section 5.7.1. Partially filling Guttrum Forest in autumn/winter 2021 has also been identified as a tier 2 watering action under all scenarios. This watering action aims to prime the wetland ahead of a larger fill in winter/spring 2021, and it will only be delivered if the winter/spring event is likely to proceed and there is sufficient water available at the time.
There are no plans to deliver water for the environment to Johnson Swamp, Lake Cullen and Lake Murphy in 2020– 21. If there are no natural floods, these wetlands will be allowed to draw down to oxygenate the soil, control invasive aquatic weeds and support the growth of lake-bed herbland vegetation communities that rely on periodic drying phases to develop and reproduce.
Priority carryover requirements have primarily been calculated based on the estimated volume required to support Murray hardhead sites, Guttrum Forest, Wirra-Lo wetland complex and the southern purple-spotted gudgeon in 2021–22.
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