Page 37 - VEWH Seasonal Watering Plan 2020-21
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• scenario planning, which indicates in text and table form the range and priority of potential environmental watering actions that might be delivered in the coming year under different climate and water availability scenarios. For example, it may show which environmental flows may be most important if there is less water for the environment available in a dry year, compared to an average year where there is more water available. The climate scenarios considered are drought, dry, average and wet. Section 1.3.4 explains how seasonal conditions are considered in planning. Potential environmental watering actions are listed in order of priority. Figure 1.5.3 is an example of the planning scenario table.
Figure 1.5.3 Example scenario planning table
1.5 How to read the seasonal watering plan
   Planning scenario
  Drought
 Dry
  Average
 Wet
 Expected river conditions
  • No unregulated flows
• Passing flows at reduced
• Possible spills from in spring, minor flood levels may occur
• Passing flows at may be
reduced
  • Regular spills from in spring, minor to moderate flood levels may occur
 • Large and frequent spills from moderate to major flood levels may occur
 Expected availability of water for the environment
    • 11,600 ML
  • 14,900 ML
  • 16,900 ML
   • 21,400 ML
  Potential environmental watering –
tier 1a (high priorities)
  • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
• 1 spring fresh (reach 2)
• Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
  • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
• 1 spring fresh (reach 2)
 • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
• 1 spring fresh (reach 2)
  Potential environmental watering –
tier 1b (high priorities)
   • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
 • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
 • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
  • Autumn/winter low flow (reach 1 & 2)
• Spring low flow (reach 1 & 2)
 Potential environmental watering –
tier 2 (additional priorities)
   • 1 winter fresh
 • 1 winter fresh
 • Increase duration of
spring fresh
  • 1 winter fresh
 Possible volume of water for the environment required to meet objectives
   • 10,700 ML (tier 1)
• 4,000 ML (tier 2)
  • 13,400 ML (tier 1)
• 4,000 ML (tier 2)
  • 15,600 ML (tier 1)
• 1,200 ML (tier 2)
   • 19,000 ML (tier 1)
• 4,000 ML (tier 2)
  Priority carryover requirements
 • 900 to 1,800 ML
   Assumed volume of water for the environment that will be available over the entire year: the assumed supply.
Tier 1a denotes the high-priority potential environmental watering actions that could be achieved with the assumed supply.1
Tier 1b denotes the high-priority potential environmental watering actions that are unlikely to be achieved with the assumed supply.
Additional water may need to be transferred or traded in to the system to meet demand for these watering actions. If tier 1b actions are not delivered, there may be a decline in environmental condition. Section 1.4.2 explains the VEWH’s options for efficiently managing water for the environment.1
Tier 2 potential environmental watering actions identified are critical to achieving environmental objectives in the long term and could be delivered in the current year if circumstances allow, but they can likely be deferred without significant environmental harm.
The volume that is planned to be kept in storage to achieve high-priority watering actions the following year. For the seasonal watering plan, predictions of volumes of water available and carryover are made before the beginning of a water year and are based on the best-available information. They are estimates only, and the VEWH and its program partners revise these estimates continually throughout the water year.
    1 Where system supply cannot be reliably determined in advance the highest priority watering actions for the year are all classified as Tier 1.
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