Transcript Impacts of Climate Change on the Northwest

Climate impacts on the Pacific Northwest
environment: Hydrology and water resources
Dennis P. Lettenmaier
Department of Civil and Environmental Engineering
and
Climate Impacts Group
University of Washington
Characteristics of the current PNW climate
Annual PNW Precipitation
(mm)
Hydrologic Characteristics of PNW Rivers
Normalized Streamflow
3.0
2.5
Snow
Dominated
2.0
Transient Snow
1.5
Rain Dominated
1.0
0.5
0.0
10 11 12
1
2
3
4
Month
5
6
7
8
9
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
Columbia River Apr-Sep streamflow
105 cubic feet per second
5
4
3
2
1
0
1900
1920
1940
1960
1980
2000
Sensitivity of Snow-dominated and Transient Rivers
to Changes in Temperature and Precipitation
900000
700000
600000
500000
400000
300000
200000
100000
1974
1974
1974
1974
1974
1974
1974
1974
1974
1974
1973
1973
1973
1973
1973
0
1973
•Streamflow timing is altered
• Annual volume stays about
the same
800000
Flow (cfs)
Temperature warms,
precipitation unaltered:
Water Year
900000
800000
600000
500000
400000
300000
200000
100000
1974
1974
1973
1973
1973
1973
1973
0
1973
•Streamflow timing stays about the same
•Annual volume is altered
700000
Flow (cfs)
Precipitation increases,
temperature unaltered:
Water Year
800000
Forecast1
700000
Forecast2
600000
Forecast3
500000
Forecast4
400000
Forecast5
Forecast6
300000
Forecast7
200000
Forecast8
100000
High Climatology
Month
sep
aug
jul
jun
may
apr
mar
feb
jan
dec
nov
0
oct
Streamflow (cfs)
1998 cool PDO/warm ENSO
Low Climatology
Observed Virgin
Flow
800000
700000
Forecast1
1999 cool PDO/cool ENSO
Forecast2
600000
Forecast4
Forecast5
500000
Forecast6
400000
Forecast7
300000
Forecast8
Forecast9
200000
Forecast10
100000
Forecast11
Forecast12
Month
sep
aug
jul
jun
may
apr
mar
feb
jan
dec
nov
0
oct
Streamflow (cfs)
Forecast3
High Climatology
Low Climatology
Observed Virgin Flow
Forecast1
800000
Forecast2
700000
Forecast3
600000
Forecast4
Forecast5
500000
Forecast6
400000
Forecast7
300000
Forecast8
200000
Sim Min
100000
Sim Max
Observed Virgin Flow
sep
aug
jul
jun
may
apr
mar
feb
jan
dec
nov
0
oct
Streamflow (cfs)
2001 cool PDO/ENSO neutral
Temperature trends in the PNW
•
US Historical Climate
Network data
•
113 stations with long
records
•
Almost every station
shows warming
•
Urbanization not a major
source of warming
Observed temperature trend
Historic Analogues for the Effects
of Climate Change
Unusually Warm Year
Ollalie Meadows (3700 ft elevation) WY 1992
Near Normal Precipitation Warm Temperatures ( + 3.5 F)
normal precipitation
normal snowpack
Effect of 1992 Winter Climate on Two PNW Rivers
1200
1000
Flow (cfs)
(caused predominantly by
warm temperatures)
800
1992
600
avg
400
200
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Dec
Oct
Jan
0
Nov
Cedar River
Western Cascades
600000
400000
1992
300000
avg
200000
100000
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Dec
Nov
0
Oct
(caused both by warm
temperatures and
decreased precipitation)
500000
Flow (cfs)
Columbia River
at The Dalles
Climate change: Predictions for
the next century
54
53
52
51
50
49
48
47
46
45
44
s
20
40
s
20
20
s
20
00
s
19
80
s
19
60
s
19
40
s
19
20
s
warmest scenario
average
coolest scenario
observed
CGCM1
00
19
Degrees F
Northwest warming
Precipitation changes
low
mean
high
precipitation
Apr-Sep Oct-Mar
-4%
0%
+4%
+8%
+9%
+22%
Estimated climate change from 20th c. to 2040s using 8
climate model scenarios.
Climate models: The
current climate
Interpreting the hydrologic effects
The main impact: less snow
April 1
Columbia
Basin
Snow
Extent
Columbia Basin Average Snow Water Equivalent
HadCM2 (Warm/Wet) and ECHAM4 (Warm/Dry) Scenarios
Basin Average Snow Water Equivalent (mm)
Snow Accumulation and Ablation
200
180
160
140
Base
120
HC 2025
100
MPI 2025
80
HC 2045
60
MPI 2045
40
20
0
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Conclusion:
Both Warm/Wet and Warm/Dry scenarios result in reduced SWE
Other sectors (forests, fish, …)
Forests
Vegetation carbon
Vegetation modeling for 2070-2100
including effects of changes in
•temperature
•precipitation (seasonality?)
•CO2 (uncertain)
Longer, hotter summers likely to
take a toll on Northwest forests even
with CO2 fertilization
Courtesy Ron Neilson, OSU
and climate damage
Floods
Low summer
streamflow, high temp
????
Estuary conditions: prey, predators,
competitors
Impacts of climate change on the
PNW
Highest confidence:
Models: warmer; higher snow line
•summer water supply, drought
•demand for water
•conflicts over water resources
•winter streamflow increases in
snowmelt-driven basins
•coastal flooding, inundation
•salmon freshwater survival
energy production
Are we prepared for a changing climate?
Natural resource management presently assumes
that
Climate does not change
But what if it does?
Adaptation pathways
Assess the problem, identify vulnerabilities
Long-term planning for reduced summer
water
Incorporate strategies into water policy