Understanding the Effects of Climate
Change on Water Resources in the
Pacific Northwest
Alan F. Hamlet,
Philip W. Mote,
Dennis P. Lettenmaier
•JISAO/CSES Climate Impacts Group
•Dept. of Civil and Environmental Engineering
University of Washington
Recession of the Muir Glacier
Aug, 13, 1941
Aug, 31, 2004
Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia
http://nsidc.org/data/glacier_photo/special_high_res.html
3.00
Canada
PNW
USA
Linear Trend (Deg. C per century)
CA
CRB
2.50
Tmax
2.00
GBAS
PNW
1.50
1.00
0.50
0.00
-0.50
-1.00
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
CA
GB
CRB
Linear Trend (Deg. C per century)
4.00
CA
3.50
CRB
Tmin
3.00
GBAS
PNW
2.50
2.00
1.50
1.00
0.50
0.00
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Trends in April 1 SWE 1950-1997
Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P., 2005, Declining
mountain snowpack in western North America, BAMS, 86 (1): 39-49
As the West warms,
spring flows rise
and summer flows
drop
Stewart IT, Cayan DR,
Dettinger MD, 2005:
Changes toward earlier
streamflow timing across
western North America, J.
Climate, 18 (8): 1136-1155
Projections for the Future Using
Global Climate Models
Natural AND human influences explain the observations of
global warming best.
Natural Climate Influence
Human Climate Influence
All Climate Influences
Observed 20th century variability
°C
+3.2°C
+1.7°C
+0.7°C
0.9-2.4°C
0.4-1.0°C
Pacific Northwest
1.2-5.5°C
Observed 20th century variability
%
+6%
+1%
+2%
-1 to +3%-1 to +9%
Pacific Northwest
-2 to +21%
Hydroclimatology of the Pacific Northwest
Annual PNW Precipitation (mm)
Winter climate in the mountains
is the key driver of streamflow.
Snowpack functions as a
natural reservoir.
Elevation (m)
Hydrologic Characteristics of PNW Rivers
Normalized Streamflow
3.0
2.5
Snow
Dominated
2.0
Transient Snow
1.5
Rain Dominated
1.0
0.5
0.0
10 11 12
1
2
3
4
Month
5
6
7
8
9
Effects of the PDO and ENSO on Columbia River
Summer Streamflows
PDO
450000
Cool
Cool
Warm
Warm
350000
300000
250000
200000
high
high
low
low
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
150000
1900
Apr-Sept Flow (cfs)
400000
Warming Affects Streamflow Timing
900000
Black: Obs
Red: 2.3° C warming
700000
600000
500000
400000
300000
200000
100000
Water Year
1974
1974
1974
1974
1974
1974
1973
1973
1973
1973
1973
0
1973
•Streamflow
timing is altered
• Annual volume
may be
somewhat lower
due to increased
ET
800000
Flow (cfs)
Temperature
warms,
precipitation
unaltered:
Precipitation Affects Streamflow Volume
900000
Black -- Obs
Blue -- 9% increase in precip.
700000
600000
500000
400000
300000
200000
100000
Water Year
1974
1974
1974
1974
1974
1974
1973
1973
1973
1973
1973
0
1973
•Streamflow
timing stays
about the same
•Annual volume
is altered
800000
Flow (cfs)
Precipitation
increases,
temperature
unaltered:
Hydrologic Impacts for the PNW
Schematic of VIC Hydrologic Model and
Energy Balance Snow Model
6 km
6 km
1/16th
Deg.
PNW
Snow Model
The warmest locations that accumulate
snowpack are most sensitive to warming
+2.3C,
+6.8%
winter
precip
Simulated Changes in Natural Runoff Timing in the Naches
River Basin Associated with 2 C Warming
120
Simulated Basin Avg Runoff (mm)
100
•Increased winter flow
•Earlier and reduced peak flows
•Reduced summer flow volume
•Reduced late summer low flow
80
1950
60
plus2c
40
20
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Rain Dominant
250
Simulated Basin Avg Runoff (mm)
Chehalis River
200
150
1950
plus2c
100
50
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Warm Transient Snow
500
Hoh River
Simulated Basin Avg Runoff (mm)
450
400
350
300
1950
250
plus2c
200
150
100
50
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Cooler Transient Snow
200
Nooksack
River
Simulated Basin Avg Runoff (mm)
180
160
140
120
1950
100
plus2c
80
60
40
20
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Snowmelt Dominant
450
Skagit River
Simulated Basin Avg Runoff (mm)
400
350
300
250
1950
plus2c
200
150
100
50
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Changes in Simulated April 1
Snowpack for the Canadian
and U.S. portions of the
Columbia River basin
(% change relative to current climate)
20th Century Climate
“2040s” (+1.7 C)
-3.6%
-21.4%
April 1 SWE (mm)
“2060s” (+ 2.25 C)
-11.5%
-34.8%
Effects of Basin Winter Temperatures
120000
100000
80000
Base
60000
comp 2040
40000
20000
aug
jun
apr
feb
dec
0
oct
Northern Location
(colder winter temperatures)
Average Flow (cfs)
CORRA LINN
140000
120000
100000
80000
Base
60000
comp 2040
40000
20000
aug
jun
apr
feb
dec
0
oct
Southern Location
(warmer winter temperatures)
Average Flow (cfs)
ICE HARBOR
Decadal Climate Variability and Climate
Change
Will Global Warming be “Warm and
Wet” or “Warm and Dry”?
Answer:
Probably BOTH!
450000
350000
300000
250000
200000
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
150000
1900
Apr-Sept Flow (cfs)
400000
2000
1996
1992
1988
1984
1980
1976
1972
1968
1964
1960
1956
1952
1948
1944
1940
CRB
1936
CA
1932
1928
3
1924
1920
1916
Std Anomalies Relative to 1961-1990
Regionally Averaged Cool Season Precipitation Anomalies
4
PNW
PRECIP
GB
2
1
0
-1
-2
-3
Impacts to the Columbia River
Hydro System
Impacts on Columbia Basin
hydropower supplies
• Winter and
Spring:
increased
generation
• Summer:
decreased
generation
• Annual: total
production will
depend primarily
on annual
precipitation
(+2C, +6%)
(+2.3C, +5%)
(+2.9C, -4%)
NWPCC (2005)
Warming climate impacts on
electricity demand
• Reductions in winter heating demand
• Small increases in summer air conditioning demand in
the warmest parts of the region
NWPCC 2005
Climate change adaptation may involve complex tradeoffs
between competing system objectives
Percent of Control Run Climate
2070-2098
140
PCM Control Climate and
Current Operations
120
PCM Projected Climate
and Current Operations
100
PCM Projected Climate
with Adaptive
Management
80
60
Firm
Hydropower
Annual Flow
Deficit at
McNary
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 Vol. 62, Issue 1-3, 233-256
Instream Flow Augmentation
and Water Quality
Simulated Changes in Natural Runoff Timing in the Naches
River Basin Associated with 2 C Warming
120
Simulated Basin Avg Runoff (mm)
100
•Increased winter flow
•Earlier and reduced peak flows
•Reduced summer flow volume
•Reduced late summer low flow
80
1950
60
plus2c
40
20
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Temperature thresholds for
coldwater fish in freshwater
• Warming temperatures will increasingly stress coldwater
fish in the warmest parts of our region
– A monthly average air temperature of 68ºF (20ºC) has been used as an
upper limit for resident cold water fish habitat, and is known to stress Pacific
salmon during periods of freshwater migration, spawning, and rearing
+1.7 °C
+2.3 °C
Overview of Some Water Resources
Impact Pathways
Water Supply and Demand
•Changes in the seasonality water supply (e.g. reductions in summer)
•Changes in water demand (e.g. increasing evaporation)
•Changes in drought stress
•Increasing conflicts between water supply and other uses and users of water
Energy Supply and Demand
•Changes in the seasonality and quantity of hydropower resources
•Changes in energy demand
•Increasing conflicts between hydro and other uses and users of water
Instream Flow Augmentation
•Changes in low flow risks
•Changes in the need for releases from storage to reproduce existing streamflow
regime.
•Changes in water resources management related to water quality (e.g. to provide
dilution flow or to control temperature)
Flood Control and Land Use Planning
•Changes in flood risks
•Changes in flood control evacuation and timing
•Dam safety
Impacts in Estuaries
•Impacts of sea level rise and changing flood risk on low lying areas (dikes and
levies)
•Impacts to ecosystem function
•Changes in land use policy (coastal armoring, land ownership, FEMA maps)
Long-Term Planning, Water Resources Agreements, Water Law and Policy
•Water allocation agreements in a non-stationary climate (e.g. water permitting)
•Appropriateness of the historic streamflow record as a legal definition of climate
variability
•Need for new planning frameworks in a non-stationary climate
•Transboundary implications for the Columbia Basin
Approaches to Adaptation and Planning
•Anticipate changes. Accept that the future climate will be
substantially different than the past.
•Use scenario based planning to evaluate options rather
than the historic record.
•Expect surprises and plan for flexibility and robustness in
the face of uncertain changes rather than counting on one
approach.
•Plan for the long haul. Where possible, make adaptive
responses and agreements “self tending” to avoid repetitive
costs of intervention as impacts increase over time.
Overview of Some Existing Climate Change
Water Planning Studies
•Seattle Water Supply (Wiley 2004)
•White River Basin (Ball 2004)
•Snohomish Basin (Battin et al. 2007)
•Columbia Hydro System (Hamlet et al. 1999; Payne et al. 2004, NWPCC
2005)
Ball, J. A. 2004. Impacts of climate change on the proposed Lake Tapps-White River water supply, M.S.C.E. thesis, Dept. of Civil and Environmental
Engineering, College of Engineering, University of Washington, Seattle.
Battin J., Wiley, M.W., Ruckelshaus, M.H., Palmer, R.N., Korb, E., Bartz, K.K., Imaki, H., 2007. Projected impacts of climate change on salmon habitat
restoration, Proceedings of the National Academy of Sciences of the United States of America, 104 (16): 6720-6725
Hamlet, A. F. and D. P. Lettenmaier. 1999b. Effects of climate change on hydrology and water resources in the Columbia River Basin. Journal of the
American Water Resources Association 35(6):1597-1623.
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 62:233-256.
NW Power and Conservation Council, 2007, Effects of Climate Change on the Hydroelectric System, Appendix N to the NWPCC Fifth Power Plan,
http://www.nwcouncil.org/energy/powerplan/plan/Default.htm
Wiley, M. W. 2004. Analysis techniques to incorporate climate change information into Seattle's long range water supply planning. M.S.C.E. thesis, Dept. of
Civil and Environmental Engineering, College of Engineering, University of Washington, Seattle.