www.csiro.au

Impact of Climate Change on Water Resources

Water Corporation Technical Seminars10 July 2006

Brian RyanCSIRO Marine and Atmospheric Research

Acknowledgements

IOCI Colleagues

Bureau of Meteorology,

CSIRO Marine and Atmospheric Research,

CSIRO Land and Water,

CSIRO Mathematics and Information Sciences,

Brian Sadler and Ed Hauck

And specifically Roger Jones (CMAR) for work on impact of climate change on water resources in Australia

Impact of Climate Change on Water Resources

•How has climate change?

•Is the evidence for anthropogenic climate change? (Greenhouse Gases and Aerosols)

•What can we say about the future climate?

•What is the likely impact of climate change on water resources?

•What are the threats to the water sector of climate change?

IPCC Third Assessment Report

‘An increasing body of observations give a collective picture of a warming world and other changes to the climate system’

How have surface temperatures changed?

How have sea surface temperatures in the Indian Ocean Basin changed?

How has Australian rainfall changed?

http://www.bom.gov.au/silo/products/cli_chg/index.shtml

Abrupt shifts in Australian annual rainfall

1891

1893

19721894

1967

1946

1945

1948

0102030405060708090

100110

Year

Num

ber

of s

tatio

ns

TotalPositive

1890-99

1940-45 1967-69

May-July SW WA Rainfall

How has the rainfall of South-western Western Australia changed?

Time series of SWWA rainfall (mm). Solid trace depicts early winter (May to July) totals and dotted trace late winter (August to October) totals. Means for the periods 1900 to 1974 and 1975 to 2004 are represented by horizontal lines.

How has the frequency of “wet” synoptic patterns (& June-July rainfall) changed?

Decrease in frequency of “wet” types accounts for ~50% of rainfall decrease

Decrease in rainfall associated with “troughs to west” types accounts for ~30%

Summary of how the Regional Climate of SWWA has changed.

Temperatures have increased by about 0.8C since 1910 with most of increase since 1950

Daily minimums have increased more than daily maximums

Sea surface temperatures in the averaged over the Indian Ocean basin have increased by 0.6C

Since 1970 the number of storms have decreased and they bring less rain

Annual rainfall has decreased by 10% since 1970s

May-July rainfall has decreased by 15% since 1970s

Reduced rainfall has resulted in 50% less runoff

Key Message: Water managers can not assume that the climate baselines of the 20th century will be valid in the 21st century

Is it possible to model the observed temperature and rainfall changes?

What can we say about the attribution of the drying in SWWA

The decline in the number of storms is linked with large-scale global circulation changes (in about 1970);

It is feasible that the drying trend could have been the result of unforced climate variability;

However, the decline in rainfall is also consistent with the modelled effect of anthropogenic forcing;

Changes in land cover may also have contributed to the rainfall decline.

What can we say about the future?

Emission scenarios

Global Temperature Rise

Global temperatures and sea level are projected to rise under all IPCC emission scenarios

Projected warming of 1.4-5.8oC between 1990 and 2100

Projected warming of 0.54-1.24oC between 1990 and 2030

Projected warming of 1.17-3.77oC between 1990 and 2070

At least half of uncertainly relates to uncertainties in emissions, the rest to uncertainties in climate science

Changes will persist for centuries

SRES 550 ppm 450 ppmMay to October

November to April

0 1 2 3 4 5 6 7 8

Temperature Change (oC)

0 1 2 3 4 5 6 7 8

Temperature Change (oC)

0 1 2 3 4 5 6 7 8

Temperature Change (oC)

0 1 2 3 4 5 6 7 8

Temperature Change (oC)

0 1 2 3 4 5 6 7 8

Temperature Change (oC)

0 1 2 3 4 5 6 7 8

Temperature Change (oC)

2030

2070

SWWA: Range of projections for changes of temperature from nine international models

SWWA: Range of projections for changes of rainfall from nine international models

-80 -60 -40 -20 0 20 40 60 80

Rainfall Change (%)

-80 -60 -40 -20 0 20 40 60 80

Rainfall Change (%)

-80 -60 -40 -20 0 20 40 60 80

Rainfall Change (%)

-80 -60 -40 -20 0 20 40 60 80

Rainfall Change (%)

-80 -60 -40 -20 0 20 40 60 80

Rainfall Change (%)

-80 -60 -40 -20 0 20 40 60 80

Rainfall Change (%)

SWWA Precipitation changes with 9 GCMs

SRES 550 ppm 450 ppmMay to October

November to April

2030

2070

Some Weather Types

1016

1000

1012

1008

1016

1004

1012

Typ

e 5

Typ

e 3

.2 .4 1.8.6

.2 .4 .6 1.8

H H

L

1016

1016

1012

1020

1012

H

L

SWWA winter weather state probabilities from stochastic downscaling of Mk3

(A2 dots, B2 small dash, B1 medium dash, A1B long dash and ‘committed’ dot-dash).

Winter Seasonal Totals

(% of median for 30 SWWA rainfall station)

Scenario 2030-2064

A2 80-90%

B2 84-91%

A1B 87-91%

B1 97-99%

S(20) 96-99%

Baseline 1975-2004

Key Message

The climate change simulations show

that even with the lowest conceivable greenhouse gas emission scenarios,

the south-west of Western Australia is projected to be drier and warmer later in the century,

with an increasing probability of dry weather patterns and a decreased probability of wet weather patterns

P and Ep changes for south-western Australia

Change per degree global warming

-20.0

-10.0

0.0

10.0

20.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cha

nge

per

degr

ee w

arm

ing

(%)

Evaporation Rainfall

P and Ep change over Australia(per degree global warming)

NW NE

SE

Tas

SW

North-west

-20.0

-10.0

0.0

10.0

20.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cha

nge

per

degr

ee w

arm

ing

(%)

Evaporation Rainfall

South-west

-20.0

-10.0

0.0

10.0

20.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cha

nge

per

degr

ee w

arm

ing

(%)

Evaporation Rainfall

North-east

-20.0

-10.0

0.0

10.0

20.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cha

nge

per

degr

ee w

arm

ing

(%)

Evaporation RainfallSouth-east

-20.0

-10.0

0.0

10.0

20.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cha

nge

per

degr

ee w

arm

ing

(%)

Evaporation RainfallTasmania

-20.0

-10.0

0.0

10.0

20.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cha

nge

per

degr

ee w

arm

ing

(%)

Evaporation Rainfall

What is the likely impact of climate change on water resources?

Hydrological model sensitivity

Relate change in mean annual rainfall and potential evaporation to mean annual change in runoff (%)

∂Q = ∂P × A + ∂Ep × B

The further A and B are from zero, the more sensitive that factor is

Hydrological model sensitivityModel comparison

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

0.0 1.0 2.0 3.0 4.0 5.0

A Factor (Rainfall)

B F

act

or

(Po

ten

tial E

vap

)

Simhyd

AWBM

Zhang01

Simple model of mean flow changes – MDB (2030)

-40

-30

-20

-10

0

10

20

Upper

Mur

ray

Kiewa

Ovens

Broke

n

Goulbu

rn

Campa

spe

Lodd

on

Avoca

Mur

ray R

iverin

a

Mur

rum

bidge

e

Lake

Geo

rge

Lach

lan

Benan

ee

Mall

ee

Wim

mer

a-Avo

n

Borde

r

Moo

nie

Gwydir

Namoi

Castle

reag

h

Mac

quar

ie-Bog

an

Conda

mine

-Culg

oa

War

rego

Paroo

Darlin

g

Lower

Mur

ray

Cha

nge

in m

ean

annu

al f

low

(%

)

Vertical lines measure range from ten models with a global warming range from 0.54-1.24C. The central box is range of change at 0.85C (median) global warming

Provisional results relating runoff response to climate change for the MDB

0 1 2 3 4 5 6

20

10

0

-10

-20

-30

Mean Global Warming (°C)

Mea

n R

ain

fall

Cha

nge

(%)

25-50

0-25

-25-0

-50--25

-75--50

2030 SRES

2100 WRE

2100 SRES

25 to 50

0 to 25

-25 to 0

<-50

-50 to -25

Mean Runoff

Change (%)

-70

-60

-50

-40

-30

-20

-10

0

Albany

Coa

st

Denm

ark R

iver

Kent R

iver

Frank

land

River

O'Sha

nnon

Rive

r

War

ren

River

Donne

lly R

iver

Blackw

ood

River

Busse

lton

Coast

Presto

n Rive

r

Collie

River

Harve

y Rive

r

Mur

ray R

iver (

WA)

Avon

River

Swan C

oast

Moo

re-H

ill Rive

rs

Cha

nge

in m

ean

annu

al f

low

(%

)

Simple model of mean flow changes – SW WA (2030)

Vertical lines measure range from ten models with a global warming range from 0.54-1.24C. The central box is range of change at 0.85C (median) global warming

Reduction in mean monthly inflow to Stirling Dam (Berti et al 2004) using the current (1982-2002)and future (2042-2062) GCM simulations

0

750

1500

2250

3000

3750

4500

5250

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Vol

ume

redu

ctio

n in

infl

ow (M

L)

.

0%

10%

20%

30%

40%

50%

60%

70%

Perc

enta

ge re

duct

ion

in in

flow

(%) .

Flow change (ML)Flow change (%)

Annual % decrease in stream flow is 31%

IOCI “Living with our changing climate workshop”

Key Impacts on Water Sector Reduced reliability of public supply

Reduced reliability of private supply

Reduced stream and estuary flow and water quality reducing ecological and social values

Drying of ground water reliant systems

Reduced water availability for fire fighting

Challenged regulatory and management systems

Seasonally variable flooding

Stranded underperforming assets and infra structure

IOCI “Living with our changing climate workshop”

Water Sector Climate Science Priorities Better understanding of the dynamics of climate change

and variability, including rainfall for south-west WA, to provide data for policy and planning;

Developing of probabilities around climate scenario estimates;

Distinguishing between climate change and climate variability;

Differentiating effects on summer and winter rainfall;

Breaking down spatial trends between north to south and east and west, and even within the south-west; and

Understanding of meteorological shifts that have or will occur.

www.csiro.au

Thank You

Contact

Name: Dr Brian RyanPhone: 61 3 9333 6554Email:brian.ryan@csiro.auWeb: www.marine.csiro.au

Contact CSIRO

Phone: 1300 363 400+61 3 9545 2176Email: enquiries@csiro.auWeb: www.csiro.au