Meeting Environmental Flow Objectives

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Meeting Environmental Flow Objectives
Stephen BeareABARE
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Specifying environmental demands

• Moving from quantity to objective based demands
• Working with uncertainty
• Volumes
• Timing
• Efficient delivery

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A case studyMurrumbidgee River

• Reconnecting lagoons and billabongs along the
  central river reaches
• Supplementary dam releases
• Key characteristics of a high flow event
• Frequency
• Timing
• Duration

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Developing an optimal release strategy

• Minimise expected costs
• For a specified event
• A maximum desired duration between events
• Reliability of success/penalty for failure
• Given
• The cost of water on call
• The opportunity cost of water released
• Current flow and climatic conditions

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An example

• Targeted event
• A minimum flow of 30 GL/day at Wagga
• Over 14 days
• Within an August to September window
• Occurring
• At least every five years
• With a reliability of 95 per cent
• Given
• Cost of an entitlement 1500/ML
• With an opportunity cost of 20/ML

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Environmental demand

• Average water requirement 25 GL/year
• Average release 75 GL
• Water on call 142GL

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Advantages of a decision model

• Environmental demands are well specified
• Objectives
• Expected volume of water required
• Evaluation and adaptation
• Systematic evaluation of alternative objectives
  and strategies
• Biophysical impacts
• Costs

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Alternative release targets

• 14 day event
• 5 day fill 5 day flush
• 3 day fill 3 day flush

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Total costs of the alternative release targets
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Bringing the costs down further

• Lower security entitlements
• Trading with irrigators
• Options contracts water cost saving of 70
  percent
• Improved forecasting

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With acknowledgmentAnna Heaney Terry Hillman
Ray Hinde Ilan Salbe
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Paper is availablefromsbeare_at_abare.gov.au or