Page 225 - VEWH Seasonal Watering Plan 2020-21
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Table 5.2.10 Potential environmental watering actions and objectives for the Hattah Lakes
1 The Hattah Lakes pump station may also be operated at any time of year for annual maintenance requirements.
Scenario planning
Table 5.2.11 outlines the potential environmental watering and expected water use under a range of planning scenarios.
Environmental watering is planned under all scenarios during 2020–21. The magnitude, extent and duration of environmental watering will increase through the spectrum of dry, average and wet scenarios.
In the absence of a natural flood, the highest-priority potential watering action will be to fill up selected wetlands in the southern Hattah Lakes in autumn/winter 2021. Under drought and dry scenarios, water for the environment should target the lowest-lying wetlands: Lakes Bulla, Hattah, Little Hattah, Lockie, Yewell and Yerang. Watering these wetlands would create a mosaic of wetland habitats within the southern Hattah Lakes that are at different stages of their wetting and drying cycle and provide significant refuge for waterbirds and terrestrial fauna in a generally dry landscape.
Under an average scenario, potentially significant local rainfall and higher flows in the Murray River may provide
an environmental cue to wet more wetlands. This would provide benefits for a larger area of native vegetation, increase the total amount of available habitat for waterbirds and provide the first opportunity in several years to grow waterbird populations.
If the potential watering actions planned for autumn/winter under the dry and average scenarios begin and cannot be completed by 30 June 2021, it will be necessary to continue watering into the 2021–22 water year.
In a wet scenario, natural flow is expected to wet Hattah Lakes, and environmental water may be used to extend the duration and extent of wetting to ensure parts of the floodplain that rely on natural floods are watered. Little or no environmental watering may be needed to supplement a large flood, but if there is only moderate natural flooding, the Hattah pumps may be used to enhance environmental outcomes.
The tier 2 watering actions that are identified would
target extra wetlands and the floodplain to broaden the area watered and increase the overall environmental benefits. The tier 2 watering actions could be delivered if circumstances allow, but they can likely be deferred without significant environmental harm.
5.2 Victorian Murray system
 Potential environmental watering action1
  Functional watering objectives
    Environmental objectives
   Southern Hattah Lakes (fill of selected wetlands during autumn/winter 2021)
• Stimulate the growth and improve the condition of river red gums
• Provide refuge and feeding habitat for waterbirds
• Stimulate the growth of aquatic vegetation in wetlands that are currently dry
          Hattah Lakes (floodplain inundation up to 45.0 m AHD at any time if there is a natural flood)
• Wet river red gums and black box on the floodplain to stimulate growth and improve the condition of mature trees
• Provide suitable soil conditions for the germination of black box trees on the floodplain and support the growth of trees that germinated in the flows provided in 2017
• Provide suitable conditions to support waterbird and woodland bird breeding and feeding
• Provide connections to allow native fish to move between Hattah Lakes and the Murray River
• Provide spawning and recruitment habitat for small-bodied native fish and nursery habitat for large-bodied native fish (such as golden perch)
           Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21 | 223

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