Transcript Slide 1

Transboundary Implications
of Climate Change for the
Columbia River Basin
Alan F. Hamlet,
Philip W. Mote, Nate Mantua,
Dennis P. Lettenmaier
•JISAO/CSES Climate Impacts Group
•Dept. of Civil and Environmental Engineering
University of Washington
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 long-term transboundary agreements)
should be informed by the best and most complete climate
information available, but frequently they are not.
Global Climate Change Scenarios
and Hydrologic Impacts for the PNW
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
%
-1 to +3%
+1%
+6%
+2%
-1 to +9%
Pacific Northwest
-2 to +21%
The warmer locations are most
sensitive to warming
2060s
+2.3C,
+6.8%
winter
precip
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
Changes in Simulated April 1
Snowpack for the Canadian
and U.S. portions of the
Columbia River basin
(% change relative to current climate)
20th Century Climate
“2040s” (+1.7 C)
-3.6%
-21.4%
April 1 SWE (mm)
“2060s” (+ 2.25 C)
-11.5%
-34.8%
Simulated Changes in Natural Runoff Timing in the Naches
River Basin Associated with 2 C Warming
120
Simulated Basin Avg Runoff (mm)
100
80
Impacts:
•Increased winter flow
•Earlier and reduced peak flows
•Reduced summer flow volume
•Reduced late summer low flow
1950
60
plus2c
40
20
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Effects of Basin Winter Temperatures
120000
100000
80000
Base
60000
comp 2040
40000
20000
aug
jun
apr
feb
dec
0
oct
Northern Location
(colder winter temperatures)
Average Flow (cfs)
CORRA LINN
140000
120000
100000
80000
Base
60000
comp 2040
40000
20000
aug
jun
apr
feb
dec
0
oct
Southern Location
(warmer winter temperatures)
Average Flow (cfs)
ICE HARBOR
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
8000
7000
6000
5000
4000
3000
2000
1000
0
Sep
20000
15000
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
Nov
10000
Oct
Jul
Full
25000
Storage
: Current Climate
Aug
Jun
Apr
May
Mar
Feb
Jan
Dec
Oct
30000
Nov
Reservoir Inflow
Flood Control vs. Refill
Flood Control vs. Refill
Streamflow timing shifts can reduce the reliability of reservoir refill
8000
+ 2.25 oC
6000
5000
4000
3000
30000
Full
2000
1000
25000
: Current Climate
Storage
Sep
Jul
Aug
Jun
Apr
May
Mar
Jan
Feb
Dec
Oct
0
Nov
20000
: + 2.25 oC No adaption
15000
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
Nov
10000
Oct
Reservoir Inflow
7000
Flood Control vs. Refill
Streamflow timing shifts can reduce the reliability of reservoir refill
8000
7000
+ 2.25 oC
5000
4000
30000
3000
Full
2000
1000
: Current Climate
Storage
Aug
25000
Sep
Jul
Jun
Apr
May
Mar
Jan
Feb
Dec
Oct
0
Nov
20000
: + 2.25 oC No adaption
15000
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
10000
Nov
: + 2.25 oC plus adaption
Oct
Reservoir Inflow
6000
Temperature thresholds for
coldwater fish in freshwater
• Warming temperatures will increasingly stress coldwater
fish in the warmest parts of our region
– A monthly average air 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 Transboundary Water
Management in the Columbia Basin
•Climate change will result in significant hydrologic changes in the
Columbia River and its tributaries.
•Snowpack in the BC portion of the Columbia basin is much less sensitive
to warming in comparison with portions of the basin in the U.S. and
streamflow timing shifts will also be smaller in Canada.
•As warming progresses, Canada will have an increasing fraction of the
snowpack contributing to summer streamflow volumes in the Columbia
basin.
•These differing impacts in the two countries have the potential to
“unbalance” the current coordination agreements, and will present
serious challenges to meeting instream flows on the U.S. side.
•Changes in flood control, hydropower production, and instream flow
augmentation will all be needed as the flow regime changes.
Implications for the Columbia River Treaty
•The Columbia River Treaty is focused primarily on
conjunctive hydropower and flood control operations.
•Arguably the greatest shortcoming of the agreement in the
context of climate change adaptation is that currently the
CRT does not encompass tradeoffs between the full range of
management concerns facing the US and Canada.
•Of particular concern is the need to encompass the different
(and often competing) ecosystem needs in Canada and the
US.
•Does the Columbia River Treaty have the flexibility and
scope needed to adapt to the water resources challenges of
the 21st Century?
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
ftp://ftp.hydro.washington.edu/pub/hamleaf/climate_change_white_papers
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
Book Chapter on Transboundary Challenges in the Columbia Basin
ftp://ftp.hydro.washington.edu/pub/hamleaf/transboundary_climate_change