Unprecedented Drought Climate Change and the MurrayDarling Basin

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Unprecedented DroughtClimate Change and the
Murray-Darling Basin

• Bruce Campbell
• Special Projects Engineer
• Murray-Darling Basin Commission
• November 2008

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Outline

• Geography Murray-Darling Basin introduction
• Defining this drought
• What is different?
• Climate Variability and Climate Change
• Lessons
• Water management during the worst drought on
  record

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Drought Planning
From Climate extremes in Australia the role of
risk management (2002), after Don Wilhite. Dingle
Smith, Centre for Resource and Environmental
Studies, Australian National University
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Where is the Murray-Darling Basin?Australias
relative size and latitude
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Geography

• 14 of Australia
• 1 Million Square Kilometers
• Over 2 Million People
• Major river systems
• Murray River 2530 km
• Darling River 2740 km

Economic 40 of Australian agriculture - approx
14 billion 70 of irrigated agriculture - approx
7 billion Environment Alpine rainforest to
arid rangelands World heritage convention
listings At least 35 endangered birds - At least
16 endangered mammals

• River Murray system
• Runoff, Diversions and Storage
• 9,100 GL median annual runoff
• 4,300 GL average diversions
• 9,500 GL MDBC major storage

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More GeographyRainfall Distribution
Major Storages Hume Dam (3038 GL) Dartmouth Dam
(3906 GL) Menindee Lakes (1730 GL) Lake
Victoria (677GL)
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The Murray an exotic river

• Less than 5 of the Basin yields gt 50 flow
• Large in scale but less flow in an average year
  than the Amazon in a day
• Highly variable
• Highly developed but thus high vulnerability
• Future health influenced by climate change,
  landuse, bush fires, forestry and water resources
  policy reform

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Defining this drought1. Worst year on record
2006/07
18 month Rainfall Deciles May 2006-October 2007
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Defining This Drought 1. Unprecedented low
inflows in 2006/07
2006/07 inflows 900 GL (45) less than 1914/15
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Droughts and Flooding RainsThis long drought is
the worst
River Murray system inflows
Lowest inflows for all sequences up to 10 years
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2. Pressure on Precious Resources Surface Water
Over-Allocation
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3. MDBs Recent Climate is Hotter and Drier 1C
temperature increase 4 evaporation increase
15 runoff decrease
Global average temperature
Murray-Darling average temperature
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Murray Water Use 1991 - 2009
?
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So is this Climate Change? River Murray inflows
- Typical CC Prediction
Source Department of Sustainability and
Environment Victoria Northern Region
Sustainable Water Strategy discussion paper 2008
Models typically predict lower rainfall and
hence streamflows for the River Murray system
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Actual Decreases in Runoff
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Climate Variability and Climate Change

• What we know
• Streamflow variability is a given
• Inflows are lower
• Over-allocation was not apparent in previous long
  droughts
• Over-allocation has exacerbated drought impacts
• Temperatures higher than previous droughts
• Higher temps higher evaporation/transpiration
  and hence reduce runoff
• ..Climate Shift concept
• Mitigation vs Adaptation

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Drought Lessons

• Extremely low inflows can threaten urban water
  supply security in the River Murray
• Repeated 2006/07 inflows are insufficient if
  storages are empty
• A more robust Minimum Reserve policy is needed

A Safety Net Governments have determined that
critical human needs are first in water
allocation hierarchy
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Drought Lessons

• Contingency measures are addictive
• Wetland disconnection - implemented for critical
  human needs remains to augment irrigation.
• If next season is dry, contingency measures will
  be less effective (or environmental cost higher)

Drought strips away the rhetoric and reveals the
true nature of water management
priorities Daniel Connell, Australian National
University 2008
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Water trade drought context 2006-2008 Water
Market Trends

• Triage of permanent plantings
• 5000 allocation transactions 235GL
• 40 of the water used in 2007/08 was traded
• Prices up to AUS1,000/ML (average AUS650/ML)
• Economic impact of drought reduced by 50

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Climate ChangeMitigation and Adaptation

• Mitigation National Focus
• Kevin Rudd has ratified Kyoto
• Cap and Trade Greenhouse Gases 2010
• Range of other incentives to change behaviour
• Adaptation Murray-Darling
• Water Allocation System
• Lower inflow sequences adopted for
  planning/setting allocations
• Major Water Policy Reform
• BASIN PLAN
• Defines Sustainable Diversion Limits surface
  and groundwater
• Provides Critical Human Needs first
• Defines desired Environmental Condition
• This drought has been the driver for adaptation
  regardless of whether human induced climate
  change is the cause or not

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www.mdbc.gov.au
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Critical Human NeedsReserve Policy Implications
Minimum unregulated inflows 900 GL/year Snowy
Inflows 370 GL/year Losses 1110 GL/year Urban
Domestic Needs 330 GL/year gt Shortfall 170
GL/year
Menindee Lakes
1700 GL
1700 GL
South Australia
Lake Victoria
Darling River
Darling River
River
River
Lake Victoria
677 GL
677 GL
Murrumbidgee
Murrumbidgee
New South Wales
Edward Wakool System
Edward Wakool System
Hume to SA Border Losses (dry year) 750 GL/year
Hume
Hume
Reservoir
Reservoir
Yarrawonga
Yarrawonga
River Murray
River Murray
Weir
Weir
3000 GL
3000 GL
SA Border to Wellington Losses (dry year) 360
GL/year
Torrumbarry Weir
Torrumbarry Weir
Snowy
Victoria
4000 GL
4000 GL
Dartmouth
Dartmouth
Reservoir
Reservoir
Murray Mouth
Murray Mouth