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Climatic Variability and Trends in the PNW
and Columbia River Basin from 1750-2003
and Projections of Climate Change Impacts
for the 21st Century
JISAO Center for Science in the Earth System
Climate Impacts Group
and Department of Civil and Environmental Engineering
University of Washington
October, 2003
http://www.hydro.washington.edu/Lettenmaier/Presentations/2003/hamlet_coastal_coe_oct_2003.ppt
Alan F. Hamlet
Philip Mote
Dennis P. Lettenmaier
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**.
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?
Hydroclimatology of the Pacific Northwest
Natural streamflow at The Dalles is determined
by what happens in the mountains in winter.
Winter precip
Oct-Mar (mm)
The Dalles
Summer precip
Apr-Sept (mm)
Elevation (m)
Pacific Decadal Oscillation
El Niño Southern Oscillation
A history of the PDO
A history of ENSO
warm
warm
cool
1900 1910
1920
1930 1940 1950
1960 1970 1980
1990 2000
1900 1910
1920
1930 1940 1950
1960 1970 1980
1990 2000
Effects of the PDO and ENSO on Columbia River
Summer Streamflows
PDO
450000
Cool
Cool
Warm
Apr-Sept Flow (cfs)
400000
Warm
350000
300000
250000
200000
high
high
low
low
Ocean Productivity
2000
1990
1980
1970
1960
1950
1940
1930
1920
1910
1900
150000
Long-Term Trends in Temperature,
Precipitation, and Streamflow
Trends in Annual Streamflow at The Dalles from 1858-1998 are strongly downward.
350000
250000
Annual
200000
5 yr mean
10 yr mean
150000
Linear (Annual)
100000
50000
0
1858
1868
1878
1888
1898
1908
1918
1928
1938
1948
1958
1968
1978
1988
1998
Annual Mean Flow (cfs)
300000
Winter precipitation and annual flow in the Columbia River are highly
correlated and are both gradually increasing since 1916
350000
(Trend ~ +7% per century)
300000
250000
200000
regressed
obs wy flow
Linear (obs wy flow)
150000
100000
y = 146.69x + 192462
50000
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
1921
1916
0
(Comparison of Annual Flow at The Dalles and Predicted Flow Based on
Oct-Mar Basin-Average Precipitation from 1916-1997)
Log10 mean flow, The Dalles, OR (cfs)
Tree-ring based reconstructions suggest that the Dust Bowl was
probably not the worst drought sequence in the past 250 years
5.5
red = observed, blue = reconstructed
5.4
5.3
5.2
5.1
5.0
1750
1775
1800
1825
1850
1875
Year
1900
1925
1950
1975
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.
2000
Building dams has fundamentally altered the flow regime.
(Peak Regulated Flow at The Dalles Since 1858)
Completion of Major Dams
Global Climate Change Scenarios
and Impacts on the PNW
The earth is warming -- abruptly
Four Delta Method Climate Change Scenarios for the PNW
Delta T, 2020s
Delta T, 2040s
5
5
~ + 1.7 C
~ + 2.5 C
4
hadCM2
3
hadCM3
2
PCM3
ECHAM4
1
Degrees C
Degrees C
4
mean
0
hadCM2
3
hadCM3
2
PCM3
ECHAM4
1
mean
0
J
F
M
A
M
J
J
A
S
O
N
D
J
-1
F
M
A
Precipitation Fraction, 2020s
J
J
A
S
O
N
D
Precipitation Fraction, 2040s
1.75
1.75
1.5
1.5
hadCM2
hadCM3
1.25
PCM3
1
ECHAM4
Fraction
Fraction
M
-1
hadCM2
hadCM3
1.25
PCM3
1
ECHAM4
mean
0.75
mean
0.75
0.5
0.5
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
A
S
O
N
D
Somewhat wetter winters and perhaps somewhat dryer summers
Changes in Mean
Temperature and
Precipitation or Bias
Corrected Output
from GCMs
VIC
Hydrology Model
ColSim
Reservoir
Model
The main impact: less snow
VIC Simulations of April 1 Average Snow Water Equivalent
for Composite Scenarios (average of four GCM scenarios)
Current Climate
2020s
Snow Water Equivalent (mm)
2040s
Naturalized Flow for Historic and Global Warming Scenarios
Compared to Effects of Regulation at 1990 Level Development
Historic Naturalized Flow
Estimated Range of
Naturalized Flow
With 2040’s Warming
Regulated Flow
Simulated Natural Streamflow (cfs)
Simulated Natural Flow in the Willamette River at the Confluence with the Columbia
Global Sea level rise
IPCC (www.ipcc.ch)
Estimates of rates of sea level rise and land uplift at the mouth of the
Columbia River are comparable in magnitude.
Rate of Change (mm/year)
3
2.5
2
Rate of Sea level Rise
1.5
Rate of Land Uplift
1
0.5
0
1
(Uplift references: Holdahl et al. 1989; Mofjeld 1989)
Strategies and Tools for Incorporating
Climate Information in
Long-Term Water Planning
Critical Period Planning Methods for Water Studies
Columbia River at The Dalles
1934
1934
1933
1933
1932
1932
1932
1931
1931
1930
1930
1930
1929
1929
1928
1928
1927
1927
1927
1926
1926
1925
1925
1925
800000
700000
600000
500000
400000
300000
200000
100000
0
Observed Streamflows
Planning Models
System Drivers
Incorporating Climate Change in Critical Period Planning
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.
Observed Streamflows
Planning Models
Altered Streamflows
Climate Change Scenarios
System Drivers
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 planning if we are to
avoid costly mistakes in forging long-term policy.
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.
Some Selected Web Resources
Link to this presentation:
http://www.hydro.washington.edu/Lettenmaier/Presentations/2003/hamlet_coastal_co
e_oct_2003.ppt
Alan Hamlet’s web site:
http://www.ce.washington.edu/~hamleaf/hamlet/alan_f_hamlet.html
Climate Impacts Group website:
http://jisao.washington.edu/PNWimpacts/Infogate.htm
CIG White papers on climate change and climate change planning:
http://jisao.washington.edu/PNWimpacts/Workshops/Skamania2001/WP01_agenda.h
tm
PNW Climate Change Streamflow Scenarios:
http://www.ce.washington.edu/~hamleaf/climate_change_streamflows/CR_cc.htm