Transcript Presentation Title, Arial Regular 29pt Sub title, Arial

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)
• 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
Rainfall and runoff characteristics
• Rainfall varies
considerably from
east to west
• 2400 mm in SE
• < 200 mm in west
• Most runoff from
small area
• Only rivers in south
are reliable
Growth in storage capacity & diversions
40,000
35,000
Volume (GL)
30,000
25,000
Capacity major storages
Average annual flow of all rivers (without-development)
Average natural flow to the sea
Total surface water diversions
20,000
15,000
10,000
5,000
0
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Murray-Darling Basin Sustainable Yields Project
• 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.
Scenarios 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
MAM
JJA
Winter
Summer
SON
DJF
Spring
Methods - overview
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
Bidgee IQQM
Lower Bidgee
MODFLOW
Murray BigMod
Murray MSM
Eastern Mt Lofty Ranges
6*WATERCRESS
Southern Riverine
Plains MODFLOW
Wimmera REALM
Daily
Weekly
Monthly
Avoca REALM
GSM REALM
Ovens REALM Mid Bidgee MODFLOW
Upper Condamine IQQM
Border Rivers MODFLOW
Mac. b and Bor. Riv IQQM
Moonie IQQM
Lower Gwydir MODFLOW
Gwydir IQQM
Upper Namoi MODFLOW
Peel IQQM
Namoi IQQM
Lower Namoi MODFLOW
Macq-Castlereagh 6*IQQM
Macquarie MODFLOW
Lachlan IQQM
Mid-Lachlan MODFLOW
Lower Lachlan MODFLOW
Snowy SIM_V9
ACTEW REALM
Upper Bidgee IQQM
The pattern of water availability
3 Condamine- Balonne
at J ac k T ay lor Weir
50
0
200
100
0
8 Mac quar ie
10 Lac hlan
at Nar r omine
at Nanami
150
100
50
0
J F M A M J J A S O N D
100
50
0
Monthly flow (GL)
Monthly flow (GL)
200
100
0
J F M A M J J A S O N D
0
at Wagga
800
600
400
200
0
J F M A M J J A S O N D
12 Mur r ay
downs tr eam of Lak e Eildon
300
200
11 Mur r umbidgee
J F M A M J J A S O N D
14 G oulbur n- Br ok en
400
400
J F M A M J J A S O N D
Monthly flow (GL)
200
150
at Bour k e
600
J F M A M J J A S O N D
Monthly flow (GL)
Monthly flow (GL)
J F M A M J J A S O N D
250
Monthly flow (GL)
100
300
9 Bar won- Dar ling
1500
17 Mur r ay
at Yar r awonga
Monthly flow (GL)
150
1 Par oo
at Caiwar r o
Monthly flow (GL)
Monthly flow (GL)
Changes in seasonality
1000
500
0
J F M A M J J A S O N D
2500
at Wentwor th
2000
1500
1000
500
0
J F M A M J J A S O N D
Relative level of surface water use
• MDB: about half of available surface water is diverted for use
• ~11,300 GL/year on average; from ~23,400 GL/year
60%
Historical climate
Median 2030 climate
Extremely high
50%
Very high
40%
High
30%
M o derately high
20%
M o derate
10%
Lo w
B
M
D
G
w
ou
yd
lb
ir
ur
nBr
ok
M
en
ur
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C
m
on
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W
im
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a
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of
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an
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on
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ac
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qu
ar
ar
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as
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re
ag
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La
ch
Lo
la
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on
-A
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ca
rd
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R
iv
er
s
M
oo
ni
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C
am
pa
sp
e
M
ur
ra
y
Pa
ro
o
0%
Ea
st
er
n
Relative level of surface water use (%)
70%
Relative level of use over 111 years
60,000
0.0
Total flow
Surface water use
Relative level of use
0.2
40,000
0.4
30,000
0.6
20,000
0.8
10,000
1.0
0
1.2
1895
1915
1935
1955
1975
1995
Relative level of use (%)
Annual volume (GL/y)
50,000
Climate change - Percent changes in runoff by 2030
Median climate change impact
Extreme climate change impact
M
ou
nt
on
-D
ar
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G
ou
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m
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W es
im
C mer
a
Lo mp a
dd a s
on pe
-A
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W ca
ar
re
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Pa
ro
o
G
w
yd
ir
N
am
La oi
c
C Bor
on
de hlan
M
d
ac am r R
iv
qu
in
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ar
B
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-C al o
n
as
tle ne
re
ag
h
O
ve
ns
Ea
st
er
n
Ba
rw
Average water availability (GL/y)
Impact of climate change on availability
• MDB: median impact is an 11 percent reduction in available water
• ~2500 GL/year on average
2,000
6,000
Historical climate
Median 2030 climate
1,500
4,500
1,000
3,000
500
1,500
0
0
ve
ns
N
am
oi
M
oo
ni
e
W
ar
re
go
W
im
Ba
m
er
rw
a
on
-D
ar
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g
O
M
Pa
tL
ro
of
o
ty
R
an
ge
s
C
350
3500
300
3000
250
2500
200
2000
150
1500
100
1000
50
500
0
0
ay
450
M
ur
r
in
eBa
G
lo
ou
nn
lb
e
ur
nBr
ok
en
M
ur
ru
m
bi
dg
ee
on
da
m
Averge surface water diversions (GL/y)
400
historical climate
La
ch
la
n
G
w
yd
ir
C
am
pa
Lo
sp
M
dd
e
ac
on
qu
A
ar
vo
ie
-C
ca
as
tle
re
ag
Bo
h
rd
er
R
iv
er
s
Ea
st
er
n
Change in volumes diverted for use
• MDB: 4 percent reduction in total diversions ~450 GL/year, with current
sharing rules
Median 2030 climate
4500
4000
N
am
oi
M
oo
Lo
ni
dd
e
M
o
nou
A
nt
vo
Lo
ca
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R
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La
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R
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W
on
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M
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M
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ac
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qu
m
ar
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dg
ie
-C
ee
as
tle
re
ag
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Ea
st
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n
C
ve
ns
50
O
W
ar
re
go
on
-D
ar
li n
g
60
Ba
rw
Pa
ro
o
Additional surface water uses (GL/y)
Additional future surface water uses
70
Streamflow loss due to groundwater extraction
Additional commercial plantation forestry
Additional farm dams
40
30
20
10
0
A land of droughts….
900
• Droughts about every ten
years
800
700
• Associated with El Nino
• Also long term cycles
900
800
700
Annual rainfall, mm
600
Annual rainfall, mm
600
500
400
300
200
100
0
1900
1920
1940
annual rain
500
moving average
Average 1900-1948
400
Average 1949-2000
median 1900-2007
Major droughts
300
1960
1980
2000
Current drought in
detail - runoff
• Not proven to be
climate change
• Runoff dramatically
down (especially
2006/7)
• Temperature increase
1.5
• Reduced autumn rain,
reduced autumn and
winter runoff
1.5
Rainfall
al temperature anomaly, degrees
1.0
Runoff
Annual temperature anomaly, degrees
1.0
0.5
0.0
-0.5
0.5
-1.0
annual Tmean anomaly
0.0
moving average
-1.5
1900
1920
1940
1960
1980
2000
SY project drought projections - eg runoff in Condamine
• 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
3500
3500
3000
3000
Climate change dry extreme
Historic
2500
Annual runoff, GL
Annual runoff, GL
2500
2000
1500
moving average
moving average
Average 1895-1948
Average 1895-1948
Average 1949-2000
1500
median 1895-2006
Average 1949-2000
1000
1000
500
500
0
1890
1910
1930
1950
1970
1990
2010
annual runoff
annual runoff
2000
0
1890
median 1895-2006
More,
longer and
more severe
dry runs
1910
1930
1950
1970
1990
2010
Mid
Wet
5
4
3
2
1
bu
rn
G
ou
l
ur
ra
y
M
Wet
M
50
bi
dg
ee
60
Mid
ur
ru
m
Dry
G
w
Historic
yd
ir
in
e
Runoff
Co
nd
am
0
70
40
30
20
10
bu
rn
ur
ra
y
G
ou
l
ur
ru
m
Wet
M
80
Mid
M
yd
ir
Dry
G
w
Historic
bi
dg
ee
Runoff
in
e
0
100
60
40
20
bu
rn
G
ou
l
ur
ra
y
M
ur
ru
m
M
G
w
yd
ir
bi
dg
ee
0
in
e
• Wet extreme similar to
historical
Dry
6
Co
nd
am
• Dry extreme and median
projections show great
impacts
Historic
7
Co
nd
am
• Impacts greater in south
Number of years a long dry run
• Climate change
projections show more,
longer and more severe
dry runs
Average proportion, %
Runoff long dry runs
Number of long dry runs
8
Key messages
• 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
• 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
Murray-Darling Basin Sustainable Yields Project
funded by
National Water Commission
www.csiro.au/partnerships/SYP.html