Water availability drought and climate change in the mdb a hydrological perspective
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Water availability, drought and climate change in the MDB: a hydrological perspective. Mac Kirby MDB Water Policy Workshop, Brisbane 21 October 2010. Outline. The Murray-Darling Basin Sustainable Yields project Results A closer look at drought Implications. The Murray Darling Basin (MDB).

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Water availability drought and climate change in the mdb a hydrological perspective

Water availability, drought and climate change in the MDB: a hydrological perspective

Mac Kirby

MDB Water Policy Workshop, Brisbane

21 October 2010


Outline
Outline hydrological perspective

  • The Murray-Darling Basin Sustainable Yields project

  • Results

  • A closer look at drought

  • Implications


The murray darling basin mdb
The Murray Darling Basin (MDB) hydrological perspective

  • 1,000,000 km2

  • 1/7 of Australia

  • 80% of basin is agriculture

  • 60% of Australia’s irrigation

  • “Food Bowl” of Australia

  • Population 2,000,000

  • 6 jurisdictions


Water availability drought and climate change in the mdb a hydrological perspective

Rainfall varies considerably from east to west hydrological perspective

2400 mm in SE

< 200 mm in west

Rainfall and runoff characteristics

  • Most runoff from small area

  • Only rivers in south are reliable


Growth in storage capacity diversions
Growth in storage capacity & diversions hydrological perspective


Murray darling basin sustainable yields project
Murray-Darling Basin Sustainable Yields Project hydrological perspective

  • Water Summit: Prime Minister and First Ministers, Nov 2006

    • CSIRO to report progressively on sustainable yields of surface and groundwater systems within the MDB

  • Estimate current and likely future (~2030) water availability in each catchment/aquifer and for the entire MDB considering:

    • climate change and other risks

    • surface-groundwater interactions

  • Compare the estimated current and future water availability to that required to meet the current levels of extractive use

  • Results reported for 18 regions and entire MDB through factsheets, summary brochures and technical reports.


S cenarios used in modelling
S hydrological perspectivecenarios used in modelling

Historic climate (1895-2006) & current development

Recent climate (1997-2006) & current development

Future climate & current development

2030 climate based on 4AR IPCC results

3 global warming levels (low, mid, high)

15 global climate models

We choose a high extreme, median and low extreme for reporting

Future climate & future development

Future development

Commercial forestry plantations

Farm dams

Groundwater extractions

Autumn

Summer

Spring

Winter


Methods overview
Methods - overview hydrological perspective


Surface and groundwater models used in the 18 mdb reporting regions
Surface and groundwater models used in the 18 MDB reporting regions

Warrego IQQM

Nebine IQQM

Paroo IQQM

Lower Balonne IQQM

St George SGCS13NT

Barwon-Darling IQQM

Middle Condamine IQQM

Condamine MODFLOW

Menindee IQQM

Upper Condamine IQQM

Bidgee IQQM

Border Rivers MODFLOW

Lower Bidgee MODFLOW

Mac. b and Bor. RivIQQM

Moonie IQQM

Murray BigMod

Lower Gwydir MODFLOW

Murray MSM

Gwydir IQQM

Upper Namoi MODFLOW

Eastern Mt Lofty Ranges

6*WATERCRESS

Peel IQQM

Namoi IQQM

Lower Namoi MODFLOW

Macq-Castlereagh 6*IQQM

Southern Riverine Plains MODFLOW

Macquarie MODFLOW

Lachlan IQQM

Wimmera REALM

Mid-Lachlan MODFLOW

Lower Lachlan MODFLOW

Avoca REALM

Daily

Snowy SIM_V9

Weekly

ACTEW REALM

GSM REALM

Monthly

Ovens REALM

Mid Bidgee MODFLOW

Upper Bidgee IQQM




Relative level of surface water use
Relative level of surface water use regions

MDB: about half of available surface water is diverted for use

~11,300 GL/year on average; from ~23,400 GL/year






Impact of climate change on availability
Impact of climate change on availability regions

MDB: median impact is an 11 percent reduction in available water

~2500 GL/year on average


Change in volumes diverted for use
Change in volumes diverted for use regions

MDB: 4 percent reduction in total diversions ~450 GL/year, with current sharing rules



A land of droughts
A land of droughts…. regions

  • Droughts about every ten years

  • Associated with El Nino

  • Also long term cycles


Current drought in detail runoff
Current drought in detail - runoff regions

  • Not proven to be climate change

  • Runoff dramatically down (especially 2006/7)

  • Temperature increase

  • Reduced autumn rain, reduced autumn and winter runoff

Runoff

Rainfall


Sy project drought projections eg runoff in condamine
SY project drought projections - eg runoff in Condamine regions

  • Reflects general pattern of drought in the MDB

  • Climate change dry extreme projection drier than historic

  • Projection uses scaled historic, hence similar pattern

  • Long dry runs with reference to historic median

Climate change dry extreme

Historic

More, longer and more severe dry runs


Runoff long dry runs
Runoff long dry runs regions

  • Climate change projections show more, longer and more severe dry runs

  • Impacts greater in south

  • Dry extreme and median projections show great impacts

  • Wet extreme similar to historical


Key messages
Key messages regions

Large proportion of surface water used for irrigation

Large year to year variation - short and long term

Large uncertainty in climate change projections - use as planning scenarios

Despite the uncertainty all scenarios say the southern basin will get drier

MDB median climate change impact is:

11 percent reduction in available water (2,500 GL/year)

4 percent reductions in water use (450 GL/year)

Impact of climate change expected to be considerably greater than ‘other risks’ BUT high uncertainty associated with climate impacts


Drought implications
Drought implications regions

  • Recent drought in some ways different to past droughts - the past may not be a reliable guide to the future

  • Need to consider scenarios outside the range of past experience, including climate change scenarios

  • In recent drought there was insufficient water for either environment or irrigation. Current expectations could not be met. Extremely challenging, may be more so in future

  • No easy fixes (more large dams irrelevant, for example)

  • Improving irrigation (hydrological) efficiency may help, but

    • Amounts to be saved may be modest

    • Need to account for return flows

    • Not lowest cost


Www csiro au partnerships syp html
www.csiro.au/partnerships/SYP.html regions

Murray-Darling Basin Sustainable Yields Project

funded by

National Water Commission