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Understanding the Effects of Climate
Change and Climate Variability on
River Recreation 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
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
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
Combined Cedar-Tolt basin wide average April 1 SWE
Simulated from HadCM3
Simulated from Observed Climate
Linear (Simulated from HadCM3)
Linear (Simulated from Observed Climate)
KAF
100
50
0
1935
1955
1975
1995
2015
2035
2055
• Transient SWE simulation from HadCM3 (A2)
GCM run (with running 10 year average smoothing)
• Simulated from observed climate shows a
declining trend of ~3KAF per decade (19352000)
• HadCM3 simulated declines ~4KAF per decade
Figure courtesy of Matt Wiley and Richard Palmer at CEE, UW
2075
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
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
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
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
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
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
Some Implications for River Recreation
Warming May Improve Fall and Winter Flow Conditions and May
Require Additional Use of Storage to Maintain Existing Flow
Regimes in Summer.
120
Simulated Basin Avg Runoff (mm)
100
80
1950
60
plus2c
40
20
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Increased Demand + Reduced Supply = Competition
•Increasing population and systematic reductions in
summer water supplies are likely to increase competition
between different uses and users of water in the West.
•Such changes will force water resources management
agencies to make complex and contentious tradeoffs
between conventional water resources objectives such as
water supply, flood control and hydropower production and
river recreation.
•Different systems may respond very differently (e.g. for
different storage to flow ratios)
Implications for Hydropower Licensing
Agreements
•Because of the long time frame of hydropower licensing agreements, considerable
changes in climate and streamflow are likely to occur during the life of the license.
•These changes will tend to “unbalance” existing tradeoffs between water resources
objectives such as hydropower, flood control, water supply, instream flow, and water
temperature. Different users and uses of water will not be impacted equally. As
warming progresses, water management plans will need to be updated regularly to
cope with what we believe will be rapidly evolving conditions.
•If current licensing agreements are not robust to these expected hydrologic
changes and do not include flexible mechanisms for updating the agreements, law
suits or other challenges to the license may be the only options as warming
progresses.
•To cope with these issues, new tools and approaches are needed to create
licensing agreements that can adapt autonomously to changing hydrologic
conditions and “rebalance” tradeoffs between different uses in a well defined and
agreed upon manner. Such approaches are technically feasible.
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.
Conclusions:
Global climate change is expected to result in important
hydrologic changes in western rivers because of impacts to
snowpack and streamflow timing. Winter flows are expected
to increase and summer flows to decline.
Some important climate change impact pathways related to
river recreation include: impacts to summer water supply
and streamflow augmentation, increasing competition for
water resources in summer, and the disruption of existing
coordination agreements.
Adaptation to a changing climate may mean a shift in the
seasonality of river recreation opportunities from summer to
winter.