alan f. hamlet philip mote dennis p. lettenmaier jisao center for science in the earth system...
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Despite a general awareness of these issues in the water planning community, there is growing evidence that future climate variability will not look like the past and that current planning activities, which frequently use a limited observed streamflow record to represent climate variability, are in danger of repeating the same kind of mistakes made more than 80 years ago in forging the Colorado River Compact. Long-term planning and specific agreements influenced by this planning (such as the long-term licensing of hydropower projects) should be informed by the best and most complete climate information available, but frequently they are not. What’s the Problem?TRANSCRIPT
Alan F. HamletPhilip Mote
Dennis P. Lettenmaier
JISAO Center for Science in the Earth System Climate Impacts Group
and Department of Civil and Environmental EngineeringUniversity of Washington
October, 2003
Considering Climate Variability and Climate Change in Long-Term Water
Planning
http://www.hydro.washington.edu/Lettenmaier/Presentations/2003/hamlet_fish_hydro_oct_2003.ppt
Example of a flawed water planning study:The Colorado River Compact of 1922
The Colorado River Compact of 1922 divided the use of waters of the Colorado River System between the Upper and Lower Colorado River Basin. It apportioned **in perpetuity** to the Upper and Lower Basin, respectively, the beneficial consumptive use of 7.5 million acre feet (maf) of water per annum. It also provided that the Upper Basin will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 7.5 maf for any period of ten consecutive years. The Mexican Treaty of 1944 allotted to Mexico a guaranteed annual quantity of 1.5 maf. **These amounts, when combined, exceed the river's long-term average annual flow**.
Despite a general awareness of these issues in the water planning community, there is growing evidence that future climate variability will not look like the past and that current planning activities, which frequently use a limited observed streamflow record to represent climate variability, are in danger of repeating the same kind of mistakes made more than 80 years ago in forging the Colorado River Compact.
Long-term planning and specific agreements influenced by this planning (such as the long-term licensing of hydropower projects) should be informed by the best and most complete climate information available, but frequently they are not.
What’s the Problem?
Overview:
•What do we know about Pacific Northwest climate variability and river flow over the past 250 years or so?
•What should we expect for the 21st century?
•How can planners bring this information to bear on long-range water planning?
Hydroclimatology of the Pacific Northwest
Annual PNW Precipitation (mm)
Elevation (m)
The Dalles
WinterPrecipitation
SummerPrecipitation
(mm)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
10 11 12 1 2 3 4 5 6 7 8 9
Month
Nor
mal
ized
Stre
amflo
w
SnowDominated
Transient Snow
Rain Dominated
Hydrologic Characteristics of PNW Rivers
Temperature warms,precipitation unaltered:
•Streamflow timing is altered• Annual volume stays about the same
Precipitation increases,temperature unaltered:
•Streamflow timing stays about the same•Annual volume is altered
Sensitivity of Snowmelt and Transient Riversto Changes in Temperature and Precipitation
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1973
1973
1973
1973
1973
1973
1974
1974
1974
1974
1974
1974
Water Year
Flow
(cfs
)
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1973
1973
1973
1973
1973
1973
1974
1974
1974
1974
1974
1974
Water Year
Flow
(cfs
)
A history of the PDOwarm
coolwarm
A history of ENSO
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
Pacific Decadal Oscillation El Niño Southern Oscillation
150000
200000
250000
300000
350000
400000
450000
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Apr-S
ept F
low
(cfs
)
Effects of the PDO and ENSO on Columbia River Summer Streamflows
Cool CoolWarm Warm
high highlow low
Ocean Productivity
PDO
Long-Term Trends in Temperature, Precipitation, and Streamflow
Area-weighted Regional Avg=1.5 F/century
Annual Precipitation TrendsFrom HCN stations
Winter precipitation and annual flow in the Columbia River are highly correlated and are both gradually increasing since 1916
y = 146.69x + 192462
0
50000
100000
150000
200000
250000
300000
35000019
16
1921
1926
1931
1936
1941
1946
1951
1956
1961
1966
1971
1976
1981
1986
1991
1996
regressedobs wy flowLinear (obs wy flow)
(Trend ~ +7% per century)
(Comparison of Annual Flow at The Dalles and Predicted Flow Based on Oct-Mar Basin-Average Precipitation from 1916-1997)
Trends in Annual Streamflow at The Dalles from 1858-1998 are strongly downward.
0
50000
100000
150000
200000
250000
300000
350000
1858
1868
1878
1888
1898
1908
1918
1928
1938
1948
1958
1968
1978
1988
1998
Ann
ual M
ean
Flow
(cfs
)
Annual
5 yr mean
10 yr mean
Linear (Annual)
1750 1775 1800 1825 1850 1875 1900 1925 1950 1975 2000Year
5.0
5.1
5.2
5.3
5.4
5.5
Log1
0 m
ean
flow
, The
Dal
les,
OR
(cfs
)
Source: Gedalof, Z., D.L. Peterson and Nathan J. Mantua. (in review). Columbia River Flow and Drought Since 1750. Submitted to Journal of the American
Water Resources Association.
The Dust Bowl was probably not the worst drought sequence in the past 250 years
red = observed, blue = reconstructed
Global Climate Change Scenarios and Impacts on the PNW
Humans are altering
atmospheric composition
The earth is warming -- abruptly
Natural Climate Influence Human Climate Influence
All Climate Influences
Natural AND human influences explain the observations best.
Emissionsscenarios we choseare “middle of the road”ones
1 BMRC2 CCC3 CCSR4 CSIRO5 ECHAM36 ECHAM47 GFDL8 HadCM29 IAP10 MRI11 CERFACS12 PCM13 GISS14 HadCM315 LMD16 CSM
Higher Predictive SkillFor Temperature
Lower Predictive SkillFor Precipitation
Climate models predict temperature more accurately than precipitation.
Precipitation Fraction, 2020s
0.5
0.75
1
1.25
1.5
1.75
J F M A M J J A S O N D
Frac
tion
hadCM2
hadCM3
PCM3
ECHAM4
mean
Delta T, 2020s
-1
0
1
2
3
4
5
J F M A M J J A S O N D
Degr
ees
C
hadCM2
hadCM3PCM3ECHAM4mean
Delta T, 2040s
-1
0
1
2
3
4
5
J F M A M J J A S O N D
Degr
ees
C
hadCM2
hadCM3
PCM3
ECHAM4
mean
Precipitation Fraction, 2040s
0.5
0.75
1
1.25
1.5
1.75
J F M A M J J A S O N D
Frac
tion
hadCM2
hadCM3
PCM3
ECHAM4
mean
Four Delta Method Climate Change Scenarios for the PNW
~ + 1.7 C ~ + 2.5 C
Somewhat wetter winters and perhaps somewhat dryer summers
ColSimReservoir
Model
VICHydrology Model
Changes in Mean Temperature and
Precipitation or Bias Corrected Output
from GCMs
Current Climate 2020s 2040s
Snow Water Equivalent (mm)
VIC Simulations of April 1 Average Snow Water Equivalentfor Composite Scenarios (average of four GCM scenarios)
The main impact: less snow
Reductions in Snowpack for PCM Scenarios(low sensitivity)
Regulated Flow
Historic Naturalized Flow
Estimated Range of Naturalized FlowWith 2040’s Warming
Naturalized Flow for Historic and Global Warming ScenariosCompared to Effects of Regulation at 1990 Level Development
0
1000
20003000
4000
5000
60007000
8000
900010
/110
/29
11/2
612
/24
1/21
2/18
3/18
4/15
5/13
6/10 7/8
8/5
9/2
Date
Inflo
w (a
cre-
ft) Simulated 20thCentury Climate2020s ClimateChange Scenario2040s ClimateChange Scenario
Effects to the Cedar River (Seattle Water Supply)for “Middle-of-the-Road” Scenarios
Frequency of Drought in the Columbia River Comparable to Water Year 1992
(data from 1962-1997)
0
2
4
6
8
10
12
14
16
Base Mean2020s
Mean2040s
ECHAM42040s
PCM2040s
Scenario
Num
ber o
f Occ
uren
ces
x 2
x 4.7
x 1.3 x 1.3
Source: Payne, J.T., A.W. Wood, A.F. Hamlet, R.N. Palmer and D.P. Lettenmaier, 2004, Mitigating the effects of climate change on the water resources of the Columbia River basin, Climatic Change (in
press).
Adaptation to climate change will require complex tradeoffs between ecosystem protection and hydropower operations
2070-2098
60
80
100
120
140
FirmHydropower
Annual FlowDeficit atMcNary
Perc
ent o
f Con
trol
Run
Clim
ate
PCM Control Climate andCurrent Operations
PCM Projected Climateand Current Operations
PCM Projected Climatewith AdaptiveManagement
Monitoring Climate Change Impacts
20th century decline in NH snow cover
R.D. Brown, J. Climate, 2000
Satellite meas.
Surface measurements
Trends in April 1 snow water equivalent, 1950-2000Mote, P.W., 2003: Trends in snow water equivalent in the Pacific
Northwest and their climatic causes. Geophysical Research Letters.
Snowmelt runoff timing trends, 1948-2000
Graphic provided by Dan Cayan, Scripps Institute of Oceanography and the USGS. To appear in Climatic Change, 2003
Strategies and Tools for Incorporating Climate Information in
Long-Term Water Planning
Broad Strategies for Incorporating Climate Variability and Climate Change in Long-Term Water Planning
Identify and Assess Climate LinkagesIdentify potential linkages between climate and resource management that could affect outcomes in the long term. What’s being left out? Are there future “deal breakers” in these omissions? (e.g. ocean productivity, glaciers maintaining summer streamflow in the short term)
Design for Robustness and SustainabilityUse modeling studies to test preferred management alternatives for robustness in the face of climate variability represented by paleoclimatic studies, conventional observations, and future climate change projections.
Identify Limits and Increase Response CapabilityUse estimates of uncertainties or “what if” scenarios to find the performance limits inherent in preferred management alternatives. How can response capability be increased?
Expect Surprises and Design for Flexibility to Changing ConditionsDesign contingency planning into management guidelines to allow for ongoing adaptation to unexpected (or uncertain) conditions without recursive policy intervention.
Observed Streamflows
Planning Models
System Drivers
Critical Period Planning Methods for Water Studies
Columbia River at The Dalles
0100000200000300000400000500000600000700000800000
1925
1925
1925
1926
1926
1927
1927
1927
1928
1928
1929
1929
1930
1930
1930
1931
1931
1932
1932
1932
1933
1933
1934
1934
Observed Streamflows
Climate Change Scenarios
Planning Models
Long term planning for climate change may include a stronger emphasis on drought contingency planning, testing of preferred planning alternatives for robustness under various climate change scenarios, and increased flexibility and adaptation to climate and streamflow uncertainty.
Altered Streamflows
System Drivers
Incorporating Climate Change in Critical Period Planning
Bias Corrected Time Series Plot for the Current Climate
Bias Corrected Time Series Plot for the Composite 2040 Scenario
Web-Based Data Archive
http://www.ce.washington.edu/~hamleaf/climate_change_streamflows/CR_cc.htm
Conclusions:
The integrated and cumulative impacts of climate variability and climate change on water resources need to be incorporated more effectively in long-term water planning if we are to avoid costly mistakes in forging long-term water and energy policies and in allocating water for future use.
Including better information on climate variability and climate change in water planning will require some changes in the way we do things, but good tools and sources of information are available to assist with the process.