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Table 5.5.3 Potential environmental watering actions and objectives for lower Broken Creek
1 Intended to be delivered year-round, subject to supply constraints. Constraints may mean these flows cannot be delivered in the non-irrigation season between mid-May and mid-August.
Scenario planning
Table 5.5.4 outlines the potential environmental watering and expected water use under a range of planning scenarios.
Due to regulation of lower Broken and Nine Mile creeks, which creates highly modified and relatively uniform conditions, environmental flow recommendations are relatively constant from year to year and independent of annual conditions.
During 2020–21, environmental flows in lower Broken Creek will be adjusted as needed to optimise the quantity of habitat and movement opportunities for native fish, maintain water quality and flush azolla through the system. The environmental flow objectives may be partly or wholly met by regulated flows to meet irrigation demand and/or by natural flow. Therefore, water for the environment will only be used to make up shortfalls. During the irrigation season, water for the environment will be mainly used to deliver high flow and freshes, because irrigation demand and the associated operational water flows are likely to meet many of the environmental low flow requirements. Outside of the irrigation season, maintaining low flow above 40 ML per day in all reaches is the primary focus to ensure ecological objectives are met.
The potential environmental watering actions in Table 5.5.4 are all considered to be high priorities and are expected
to meet the environmental requirements of the system. No tier 2 potential watering actions have been identified for 2020–21. Critical carryover requirements under all scenarios in 2020–21 ensure a minimum low flow and a small fresh can be delivered in 2021–22.
In addition to the deliveries of water for the environment explained in this seasonal watering plan, downstream environmental or operational demands may result in higher flows being delivered in lower Broken Creek in 2020–21. Higher flows through the lower Broken Creek system generally provide positive environmental outcomes.
5.5 Broken system
 Potential environmental watering action
  Functional watering objectives
    Environmental objectives
    Year-round low flow (40- 200 ML/day in reaches 3 and 4 and 40-100 ML/day in reaches 1 and 2)1
    • Provide native fish with passage through fish ladders
• Provide suitable foraging habitat for platypus and rakali (water rats), and support the movement of juveniles of both species
• Provide habitat for turtles including protection from exposure to cold in winter
• Provide flowing-water habitat and avoid winter drying of weir pools for fish, vegetation, waterbugs, platypus and turtles
• Limit suspended sediment and maintain suitable oxygen concentration
                   Winter/spring/summer/ autumn high flow (200-250 ML/day in reaches 3 and
4 and 100-150 ML/day in reaches 1 and 2 during July to May)
   • Provide habitat for fish and support fish movement, spawning and recruitment
• Flush and mobilise azolla and maintain oxygen levels in summer
         Winter/spring freshes (up to three freshes of 450 ML/day during July to September)
 • Flush and mobilise azolla, if it blooms
• Trigger fish migration and movement
         Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21 | 267

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