water availability, drought and climate change in the mdb: a hydrological perspective mac kirby mdb...
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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)
• 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 varies considerably from east to west
• 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
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Vol
ume
(GL)
Capacity major storages
Average annual flow of all rivers (without-development)
Average natural flow to the sea
Total surface water diversions
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 modellingHistoric 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
DJF JJA
SON MAM Autumn Summer
Winter Spring
Methods - overview
Surface and groundwater models used in the 18 MDB reporting regions
Paroo IQQM
Warrego IQQMNebine IQQM
Condamine MODFLOW
Middle Condamine IQQM
St George SGCS13NT
Lower Balonne IQQM
Upper Condamine IQQM
Mac. b and Bor. Riv IQQMBorder Rivers MODFLOW
Moonie IQQM
Gwydir IQQMLower Gwydir MODFLOW
Eastern Mt Lofty Ranges 6*WATERCRESS
DailyWeeklyMonthly
Barwon-Darling IQQM
Menindee IQQM
Peel IQQMUpper Namoi MODFLOW
Namoi IQQMLower Namoi MODFLOWMacq-Castlereagh 6*IQQMMacquarie MODFLOW
Wimmera REALMLachlan IQQMMid-Lachlan MODFLOWLower Lachlan MODFLOW
Ovens REALMGSM REALM
Avoca REALMSnowy SIM_V9
Murray BigModMurray MSM
Southern Riverine Plains MODFLOW
Upper Bidgee IQQMACTEW REALM
Mid Bidgee MODFLOW
Bidgee IQQMLower Bidgee MODFLOW
Th
e p
atte
rn o
f w
ater
ava
ilab
ility
Changes in seasonality3 Condamine-Balonne
at J ack Taylor Weir
0
100
200
300
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
9 Barwon-Darling
at Bourke
0
200
400
600
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
8 Macquarie
at Narromine
0
50
100
150
200
250
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
17 Murray
at Wentworth
0
500
1000
1500
2000
2500
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
11 Murrumbidgee
at Wagga
0
200
400
600
800
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
14 Goulburn-Broken
downstream of Lake Eildon
0
100
200
300
400
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
10 Lachlan
at Nanami
0
50
100
150
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
12 Murray
at Yarrawonga
0
500
1000
1500
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
1 Paroo
at Caiwarro
0
50
100
150
J F M A M J J A S O N D
Mon
thly
flow
(G
L)
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
0%
10%
20%
30%
40%
50%
60%
70%
Paro
o
Ovens
Easte
rn M
t Lof
ty Ran
ges
Barw
on-D
arlin
g
War
rego
Macqu
arie-
Castle
reag
h
Lach
lan
Lodd
on-A
voca
Bord
er R
ivers
Moonie
Campa
spe
Murra
y
Namoi
Gwydir
Goulbu
rn-Br
oken
Murru
mbidge
e
Conda
mine
-Balo
nne
Wim
mera
MDB
Rel
ativ
e le
vel o
f sur
face
wat
er u
se (
%) Historical climate Median 2030 climate
Low
Moderate
Moderately high
High
Very high
Extremely high
Relative level of use over 111 years
0
10,000
20,000
30,000
40,000
50,000
60,000
1895 1915 1935 1955 1975 1995
Ann
ual v
olum
e (G
L/y)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Relative level of use (%
)
Total flow
Surface water use
Relative level of use
Climate change - Percent changes in runoff by 2030
Med
ian
clim
ate
chan
ge
imp
act
Ext
rem
e cl
imat
e ch
ang
e im
pac
t
Impact of climate change on availability
• MDB: median impact is an 11 percent reduction in available water• ~2500 GL/year on average
0
500
1,000
1,500
2,000
Barw
on-D
arlin
g
Moonie
Easte
rn M
ount
Lofty
Ran
ges
Wim
mera
Campa
spe
Lodd
on-A
voca
War
rego
Paro
o
Gwydir
Namoi
Lach
lan
Bord
er R
ivers
Conda
mine
-Balo
nne
Macqu
arie-
Castle
reag
h
Ovens
Ave
rage
wat
er a
vaila
bilit
y (G
L/y)
Historical climate
Median 2030 climate
0
1,500
3,000
4,500
6,000
Goulbu
rn-Br
oken
Murru
mbidge
e
Murra
y
Change in volumes diverted for use
• MDB: 4 percent reduction in total diversions ~450 GL/year, with current sharing rules
0
50
100
150
200
250
300
350
400
450
Paro
o
Easte
rn M
t Lof
ty Ran
ges
Ovens
Moonie
War
rego
Wim
mera
Barw
on-D
arlin
g
Namoi
Lach
lan
Gwydir
Campa
spe
Lodd
on-A
voca
Macqu
arie-
Castle
reag
h
Bord
er R
ivers
Ave
rge
surf
ace
wat
er d
iver
sion
s (G
L/y)
historical climate Median 2030 climate
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Conda
mine
-Balo
nne
Goulbu
rn-Br
oken
Murru
mbidge
e
Murra
y
Additional future surface water uses
0
10
20
30
40
50
60
70
Paro
o
War
rego
Barw
on-D
arlin
g
Ovens
Wim
mera
Conda
mine
-Balo
nne
Moonie
Lodd
on-A
voca
Easte
rn M
ount
Lofty
Ran
ges
Campa
spe
Goulbu
rn-Br
oken
Gwydir
Lach
lan
Bord
er R
ivers
Namoi
Murra
y
Murru
mbidge
e
Macqu
arie-
Castle
reag
h
Add
ition
al s
urfa
ce w
ater
use
s (G
L/y)
Streamflow loss due to groundwater extraction
Additional commercial plantation forestry
Additional farm dams
A land of droughts….
• Droughts about every ten years
• Associated with El Nino
• Also long term cycles
0
100
200
300
400
500
600
700
800
900
1900 1920 1940 1960 1980 2000A
nnual ra
infa
ll, m
m
Major droughts
0
100
200
300
400
500
600
700
800
900
1900 1920 1940 1960 1980 2000
annual rain
moving average
Average 1900-1948
Average 1949-2000
median 1900-2007
Major droughts
Current drought in detail - runoff
• Not proven to be climate change
• Runoff dramatically down (especially 2006/7)
• Temperature increase
• Reduced autumn rain, reduced autumn and winter runoff
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
1900 1920 1940 1960 1980 2000
Annual te
mpera
ture
anom
aly
, degre
es
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
1900 1920 1940 1960 1980 2000
annual Tmean anomaly
moving average
Rainfall Runoff
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
0
500
1000
1500
2000
2500
3000
3500
1890 1910 1930 1950 1970 1990 2010
Annual ru
noff
, G
L
annual runoff
moving average
Average 1895-1948
Average 1949-2000
median 1895-2006
0
500
1000
1500
2000
2500
3000
3500
1890 1910 1930 1950 1970 1990 2010
Annu
al r
uno
ff,
GL
annual runoff
moving average
Average 1895-1948
Average 1949-2000
median 1895-2006
More, longer and more severe dry runs
Historic Climate change dry extreme
Runoff long dry runs
• 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
Runoff
0
1
2
3
4
5
6
7
8
Nu
mb
er
of
lon
g d
ry r
un
s Historic Dry Mid Wet
Runoff
0
10
20
30
40
50
60
70
Nu
mb
er
of
years
a l
on
g d
ry r
un
Historic Dry Mid Wet
Runoff
0
20
40
60
80
100
Avera
ge p
rop
ort
ion
, % Historic Dry Mid Wet
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
www.csiro.au/partnerships/SYP.html
Murray-Darling Basin Sustainable Yields Project
funded byNational Water Commission