Transcript hamlet_cbt_hydrologic_impacts_jan_2007

Understanding the Effects of Climate
Change and Climate Variability on the
Water Cycle in the Pacific Northwest
Alan F. Hamlet,
Philip W. Mote,
Dennis P. Lettenmaier
•JISAO/CSES Climate Impacts Group
•Dept. of Civil and Environmental Engineering
University of Washington
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%
Local changes in climate may be larger than regional
changes, but are also inherently more uncertain, particularly
for precipitation.
Projected Hydrologic
Changes Associated with
Warming
For areas that accumulate substantial
snowpack, the areas close to freezing in
mid-winter are most sensitive to warming.
~2060
+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)
20th Century Climate
“2040s” (+1.7 C)
-3.6%
-21.4%
April 1 SWE (mm)
“2060s” (+ 2.25 C)
-11.5%
-34.8%
20th
600
Area Average Water
(depth in mm)
Seasonal
Water Balance
Naches River
700
500
precipitation
400
swe
runoff+baseflow
soil storage
300
evapotranspiration
200
100
Century Climate
sep
aug
jul
jun
may
apr
mar
feb
jan
dec
nov
oct
0
700
precipitation
400
swe
runoff+baseflow
soil storage
300
evapotranspiration
200
100
sep
aug
jul
jun
may
apr
mar
feb
jan
dec
0
nov
+ 2.25° C
+ 4% precip
500
oct
Mid 21st Century
Scenario
Area Average Water
(depth in mm)
600
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
Simulated Changes in Natural Runoff Timing in the BC Portion
of the Columbia River Basin Associated with 2 C Warming
Basin Average Runoff (mm)
180
160
140
120
100
Runoff base
Runoff plus2C
80
60
40
20
0
oct
nov dec
jan
feb mar apr may jun
jul
aug sep
1987
1987
1986
1986
1986
1986
1985
1985
1985
1985
1984
1984
1984
1984
250
1987
1987
1986
1986
1986
1986
1985
1985
1985
1985
1984
1984
1984
1984
1983
1983
1983
1983
1982
1982
1982
1982
1981
1981
1981
1981
1980
Simulated Snow Accumulation
(mm)
450
1983
1983
1983
1983
1982
1982
1982
1982
1981
1981
1981
1981
1980
Simulated Snow Accumulation
(mm)
500
Revelstoke Area (1268m)
400
350
300
1915
250
2003
200
plus2C
150
100
50
0
300
Revelstoke Area (473m)
200
1915
150
2003
plus2C
100
50
0
1987
1987
1986
1986
1986
1986
1985
1985
1985
1985
1984
600
1984
1987
1987
1986
1986
1986
1986
1985
1985
1985
1985
1984
1984
1984
1984
1983
1983
1983
1983
1982
1982
1982
1982
1981
1981
1981
1981
1980
Simulated Snow Accumulation
(mm)
700
1984
1984
1983
1983
1983
1983
1982
1982
1982
1982
1981
1981
1981
1981
1980
Simulated Snow Accumulation
(mm)
800
Golden Area (1376m)
600
500
1915
400
2003
300
plus2C
200
100
0
700
Golden Area (827m)
500
400
1915
2003
300
plus2C
200
100
0
Is it really happening?
Regional Scale Trends in Temperature for the Western U.S. and B.C. Columbia Basin
Linear Trend (Deg. C per century)
4.00
CA
CRB
GBAS
3.00
PNW
PNWBC
2.00
1.00
0.00
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
-1.00
-2.00
Linear Trend (Deg. C per century)
5.00
CA
CRB
4.50
GBAS
4.00
PNW
PNWBC
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
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
Wide-Spread Glacial Retreat has Accompanied 20th
Century Warming.
Loss of glacial mass may increase summer flow in the short
term and decrease summer flow in the long term.
1902
2002
The recession of the Illecillewaet Glacier at Rogers Pass between 1902 and 2002.
Photographs courtesy of the Whyte Museum of the Canadian Rockies & Dr. Henry
Vaux.
Water Supply Impact Pathways
Reductions in Supply
Climate
Change
Increases in Demand
Increasing
Population
Conflicts with Other
Water Resources
Objectives
Combined
Impacts
In sensitive areas, systematic reductions in summer water
availability will decrease the yield of water supply systems.
Master's Thesis: Wiley, M.W. (2004). "Analysis Techniques to Incorporate Climate
Change Information into Seattle’s Long Range Water Supply Planning," University of
Washington
Impact Pathways Associated with Hydrologic Changes
Changes in water quantity and timing
Reductions in summer flow and water supply
Increases in drought frequency and severity
Changes in extremes
Changing flood risk (up or down)
Summer low flows
Changes in groundwater
Changes in water quality
Increasing water temperature
Changes in sediment loading (up or down)
Changes in nutrient loadings (up or down)
Changes in vegetation
Forest fire
Insects
Disease
Invasive species
Changes in outdoor recreation
Skiing
Camping
Boating