Transcript Climate Change Streamflow Scenarios for Critical Period Water

Climate Change Streamflow Scenarios for
Critical Period Water Planning Studies
JISAO Center for Science in the Earth System
Climate Impacts Group
and Department of Civil and Environmental Engineering
University of Washington
April, 2003
Alan F. Hamlet
Dennis P. Lettenmaier
Amy K. Snover
Changing Awareness of Climate Change in
the Water Management Community
~1985: Global warming?
~1995: Is global warming real?
~1997: What are the expected impacts of
climate change for our region and
our water system?
~2002: How do we include climate change
and climate uncertainty in long
term planning to reduce risks?
The primary impact pathway in the
western US: less snow
Current Climate
2020s
Snow Water Equivalent (mm)
2040s
Columbia River at The Dalles
for “Middle-of-the-Road” Scenarios
Columbia River at The Dalles
500000
400000
Base
300000
2020s
2040s
200000
100000
aug
jun
apr
feb
dec
0
oct
Average Flow (cfs)
600000
Effects to Moderate Elevation Basins in the Cascades
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
9/2
8/5
7/8
6/10
5/13
4/15
3/18
2/18
1/21
12/24
11/26
10/29
Base
2020s
2040s
10/1
Inflow (acre-ft)
Inflow to Chester Morse Lake
Project Motivation:
•Target existing planning processes at the
watershed scale
•Make streamflow scenarios freely available to
help reduce costs of including climate
uncertainty in long-term planning
(Recommendations from regional stakeholders and policy
makers attending a CIG sponsored climate change workshop
Skamania, 2001)
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
Project Goals:
•Create climate change streamflow scenarios that cover the
same period of record and are numerically consistent with the
historic record of streamflows traditionally used in water
planning studies.
•Make these streamflow scenarios freely available on the web
for a large number of river locations to facilitate the
incorporation of climate change information into existing water
planning efforts.
Choice of GCM Downscaling Methods for the
Pilot Study
Although more sophisticated methods are also available, the
“Delta” method of downscaling GCM results was chosen for the
pilot applications.
•Good fit with producing alternate versions of the historic record
used in critical period planning studies.
•Easy to understand and interpret (the project has an educational
component).
•Captures much of the regional scale information from GCM
simulations.
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
Issues with Hydrologic Model Bias
900000
800000
700000
600000
500000
400000
300000
200000
100000
0
VIC
1999
1999
1998
1997
1997
1996
1995
1995
1994
1993
1993
1992
1991
1991
1990
1989
1989
1988
1987
1987
1986
1985
Observed
1985
Streamflow (cfs)
Columbia River at The Dalles
Quantile-Based Bias Correction (Wood et al. 2002)
VIC Input = 19000
35000
30000
Flow (cfs)
25000
20000
obs
15000
vic
10000
5000
0
0
0.2
0.4
0.6
Probability of Exceedence
Bias Corrected Output = 10000
0.8
1
Bias Correction Objectives:
Raw
Bias Corrected
Result: Bias corrected hydrologic simulations are quite consistent with
observed streamflows in absolute value and climate change signals are
translated without significant distortion.
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
Goals and Objectives of Two Regional-Scale Pilot Studies
in the Pacific Northwest
Northwest Power Planning Council:
Primarily focused on reliability of the Columbia River
hydropower system. Study will use the GENESYS model.
Preliminary results in John Fazio’s talk this afternoon.
Idaho Department of Water Resources:
Primarily focused on groundwater/surface water interactions,
sustainability of irrigated agriculture in the Snake River basin,
groundwater/surface water interactions and water allocation
amongst different users and uses.
Current Streamflow Routing Locations
Some Selected Results for the Snake River Basin
(Composite Scenarios)
Planned Project Extensions
•Extend the period of record of the data to 1928-1999.
•Extend the number of climate change scenarios and the
downscaling methods used.
Summary and Conclusions
Water policy workshops (Skamania 2001) have highlighted the
need to inject climate change information into existing river basin
planning activities where possible and to provide access to free
streamflow scenarios to help reduce costs.
Because most planning studies currently use a critical period
framework, our project produces “adjusted” realizations of the
historic streamflow record based on simulations from a
physically based hydrologic model driven by simple climate
change scenarios.
The methods are flexible and portable and can be used to create
streamflow scenarios deriving from different climate model
scenarios, different downscaling methods, or different hydrologic
models.