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A Brief History of Climate Change
Sensitivity Work
JISAO Center for Science in the Earth System
Climate Impacts Group
and Department of Civil and Environmental Engineering
University of Washington
April, 2003
Dennis P. Lettenmaier
Hydrology, water resources, and
climate
• Hydrologists and water resources engineers
have always had to deal with climate, it wasn’t
just “discovered”
• But, the classical assumption is equivalent to
statistical stationarity, “the future will resemble
the past”
• Unfortunately, the future may not be like the
past, which greatly complicates planning
Natural Flow at Lee Ferry, AZ
Natural Flow at Lee Ferry Stream Gage
30
Annual Flow (BCM)
25
allocated
20.3 BCM
20
Currently
used
16.3 BCM
15
10
5
0
1900
1910
1920
1930
Annual Flow
1940
1950
10 Year Average
1960
1970
1980
Running Average
1990
2000
Evolution of interest in climate
change in hydrology
• ~1977 NAS/NRC report (various papers,
basically said “we know how to deal with
this”)
• Late 1980s AAAS study (Schaake paper
evaluating water balance issues, SE U.S.)
• Late 1980s EPA Reports to Congress
• 1990s IPCC reports USNA (~40 papers
cited on water resources and climate)
UW interest in hydrology, water
resources, and climate change
• Hydrologic sensitivities of the Sacramento-San Joaquin River
basin, California, to global warming (WRR, 1990)
• Climatic sensitivity of California water resources (JWRPM,
1991)
• Sensitivity of Pacific Northwest water resources to global
warming (Northwest-Environmental-Journal, 1992)
• Water resources implications of global warming: A U.S.
regional perspective (Climatic-Change, 1999)
• Effects of climate change on hydrology and water resources in
the Columbia River basin (JAWRA , 1999)
Effects to Snowpack
Effects to Streamflow
Number of Storage Failures
no optimization
More Storage
Less Storage
optimization
U.S. Climate Change Study Basins (Lettenmaier et al. 1999)
aug
jun
apr
60
feb
70
dec
80
oct
90
Average Flow (cfs)
Flood Control
Snake River Navigation
Snake Irrigation
McNary Fish Flow
Lower Granite Fish Flow
Grand Coulee Recreation
Non-Firm Energy
Firm Energy
VIC/ColSim 2040’s
100
Current Climate
ECHAM4 2040's
HadCM2 2040's
HadCM3 2040's
PCM 2040's
50
DALLES
600000
500000
400000
Base
ECHAM4
300000
HadCM2
200000
HadCM3
PCM
100000
0
Current Climate
2040 Composite Scenario
Inflow to Chester Morse Lake
Columbia River at The Dalles
9/2
8/5
7/8
6/10
5/13
4/15
3/18
2/18
aug
jun
apr
feb
dec
0
1/21
100000
12/24
2040s
200000
Base
2020s
2040s
11/26
300000
2020s
10/29
Base
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
10/1
400000
Inflow (acre-ft)
500000
oct
Average Flow (cfs)
600000
So what is the issue for this meeting?
• The fundamental implications of global warming for
snowmelt dominated and transient snow rivers in the
west have been well understood in the academic
community for a decade or longer.
• Lots of questions about specifics, climate model
uncertainty, etc. However, a) all models show there is a
problem in snowmelt dominated watersheds, and b) the
models are consistent with what’s been observed over
the last half century or so.
• Almost all the studies are academic – few examples
where the studies have been done by the water
management agencies, using their own tools and models
• We are to the point where the question is no longer
whether climate change is an issue, but rather how to
incorporate it into the planning process (and preferably
internalize it at the agency level)