Download The Dalles Columbia River Basin

Effects of Climate Change on
Hydropower Resources in the PNW
and Western U.S.
JISAO Center for Science in the Earth System
Climate Impacts Group
and Department of Civil and Environmental Engineering
University of Washington
March, 2006
Alan F. Hamlet
Philip W. Mote
Nathan Mantua
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**.
What’s the Problem?
Despite a general awareness of these issues in the water
planning community, there is growing evidence that future
climate variability will not look like the past and that current
planning activities, which frequently use a limited observed
streamflow record to represent climate variability, are in
danger of repeating the same kind of mistakes made more
than 80 years ago in forging the Colorado River Compact.
Long-term planning and specific agreements influenced by
this planning (such as the long-term licensing of hydropower
projects and water permitting) should be informed by the best
and most complete climate information available, but
frequently they are not.
Greenhouse Gas Concentrations are
Rising Rapidly Due to Human Activity
Natural AND human influences explain the observations of
global warming best.
Natural Climate Influence
Human Climate Influence
All Climate Influences
Temperature trends (°F per century) since 1920
cooler warmer
3.6°F
2.7°F
1.8°F
0.9°F
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
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
Columbia River Basin
Useable Storage ~35 MAF
~50% of storage is in Canada
~Storage is 30% of annual flow
Snowpack functions as a
natural reservoir
Elevation (m)
Annual PNW Precipitation (mm)
The Dalles
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
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:
Global Climate Change Scenarios
and Hydrologic Impacts for the PNW
Four Delta Method Climate Change Scenarios for the PNW
Delta T, 2020s
Delta T, 2040s
5
5
~ + 1.7 C
~ + 2.25 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 warmest locations are most
sensitive to warming
+2.3C,
+4.5%
winter
precip
Changes in Simulated April 1
Snowpack for the Canadian
and U.S. portions of the
Columbia River basin
(% change relative to current climate)
Current Climate
“2020s” (+1.7 C)
-3.6%
-21.4%
April 1 SWE (mm)
“2040s” (+ 2.25 C)
-11.5%
-34.8%
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
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
Water Resources Implications for the Columbia
River Basin
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
Adaptation to climate change will require complex tradeoffs
between ecosystem protection and hydropower operations
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
Flood Control vs. Refill
Streamflow timing shifts can reduce the reliability of reservoir refill
8000
30000
Full
7000
25000
5000
Storage
4000
3000
20000
current climate
15000
Sep
May
Apr
Mar
Feb
Jan
Dec
Nov
10000
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
Nov
0
Oct
1000
Aug
earlier flow no
adaptation
earlier flow plus
adaptation
Jul
2000
Jun
Reservoir Inflow
6000
Model experiments (see Payne et al. 2004) have shown that
moving spring flood evacuation two weeks to one month
earlier in the year helps mitigate reductions in refill reliability
associated with streamflow timing shifts.
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
Temperature thresholds for
coldwater fish in freshwater
• Warming temperatures will increasingly stress coldwater
fish in the warmest parts of our region
– A monthly average 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
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 could occur 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.
Selected References and URL’s
Climate Impacts Group Website
http://www.cses.washington.edu/cig/
White Papers, Agenda, Presentations for CIG 2001 Climate Change Workshop
http://jisao.washington.edu/PNWimpacts/Workshops/Skamania2001/WP01_agenda.htm
Climate Change Streamflow Scenarios for Water Planning Studies
http://www.ce.washington.edu/~hamleaf/climate_change_streamflows/CR_cc.htm
Northwest Power and Conservation Council Columbia Basin Hydropower Study
http://www.nwppc.org/energy/powerplan/plan/Default.htm
Refs on Climate Variability and Climate Change
http://www.ce.washington.edu/~hamleaf/hamlet/publications.html
Observed Hydrologic Changes