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Quantifying the Effects of Climate
Variability and Change on Hydrologic
Extremes in the Pacific Northwest
Region of N. America
Alan F. Hamlet
Ingrid Tohver
Se-Yeun Lee
•JISAO/CSES Climate Impacts Group
•Dept. of Civil and Environmental Engineering
University of Washington
CBCCSP Research Team
Lara Whitely Binder
Pablo Carrasco
Jeff Deems
Marketa McGuire Elsner
Alan F. Hamlet
Carrie Lee
Se-Yeun Lee
Dennis P. Lettenmaier
Jeremy Littell
Guillaume Mauger
Nate Mantua
Ed Miles
Kristian Mickelson
Philip W. Mote
Rob Norheim
Erin Rogers
Eric Salathé
Amy Snover
Ingrid Tohver
Andy Wood
http://www.hydro.washington.edu/2860/products/sites/r7climate/study_report/CBCCSP_
chap1_intro_final.pdf
The Myth of Stationarity:
1) Climate Risks are stationary in time.
2) Observed streamflow records are the best
estimate of future variability.
3) Systems and operational paradigms that are
robust to past variability are robust to future
variability.
The Myth of Stationarity Meets the
Death of Stationarity
Muir Glacier in Alaska
Aug, 13, 1941
Aug, 31, 2004
Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia
http://nsidc.org/data/glacier_photo/special_high_res.html
Why a Focus on Hydrologic Extremes?
Many human and natural systems are
quite robust under “normal” conditions,
but have the potential to be profoundly
impacted by hydrologic extreme events.
Floods
http://www.nps.gov/mora/parknews/upload/floodPP.pdf
Drought
Evacuated Reservoir During the 2001 PNW Drought
Wildfire
Low Flow and Temperature Impacts to Fish
Temperature/ Disease Related Fish Kill in the Klamath River in 2002
Dissolved Gas Management
Tailrace below Bonneville Dam
Dam Safety
Aftermath of the Johnstown Flood 1889
Dilution Flows for Industrial Pollutants
Stormwater Management
Sediment Transport and Mudslides
Historical Perspectives:
Changing Flood Risk in
the 20th Century
References:
Niemann, PJ, LJ Schick, FM Ralph, M Hughes, GA Wick, 2010: Flooding
in Western Washington: The Connection to Atmospheric Rivers, J. of
Hydrometeorology, (in review)
Hamlet AF, Lettenmaier DP (2007) Effects of 20th century warming and
climatevariability on flood risk in the western U.S. Water Resour Res,
43:W06427.doi:10.1029/2006WR005099
Observed Characteristics of Extreme
Precipitation Events
Evidence of Changing Flood Statistics
Role of Atmospheric Rivers in Flooding (Nov 7, 2006)
Niemann, PJ, LJ Schick, FM Ralph, M Hughes, GA Wick, 2010: Flooding in Western Washington: The
Connection to Atmospheric Rivers, J. of Hydrometeorology, (in review)
Role of Atmospheric Rivers in Flooding (Oct 20, 2003)
Niemann, PJ, LJ Schick, FM Ralph, M Hughes, GA Wick, 2010: Flooding in Western Washington: The
Connection to Atmospheric Rivers, J. of Hydrometeorology, (in review)
Niemann, PJ, LJ Schick, FM Ralph, M Hughes, GA Wick, 2010: Flooding in Western Washington: The
Connection to Atmospheric Rivers, J. of Hydrometeorology, (in review)
Modeling Studies of Changing 20th
Century Flood Risk in the West
Schematic of VIC Hydrologic Model
•
•
•
General Model Schematic
Sophisticated, fully distributed,
physically based hydrologic model
Widely used globally in climate
change applications
1/16 Degree Resolution
(~5km x 6km or ~ 3mi x 4mi)
Snow Model
Ln (X100 / Xmean) OBS
Avg WY Date of Flooding OBS
Evaluating the Hydrologic Model Simulations in the
Context of Reproducing Flood Characteristics
Avg WY Date of Flooding VIC
Ln (X100 / Xmean) VIC
Red = PNW, Blue = CA, Green = Colo, Black = GB
X100 GEV flood/mean flood
100-yr
Red = VIC
Blue = OBS
50-yr
20-yr
10-yr
5-yr
Zp
Regionally Averaged Temperature Trends Over the Western U.S. 1916-2003
3.00
Linear Trend (Deg. C per century)
CA
PNW
CRB
Tmax
2.50
GBAS
PNW
2.00
1.50
1.00
0.50
0.00
-0.50
-1.00
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
GB
CA
CRB
Linear Trend (Deg. C per century)
4.00
CA
3.50
CRB
Tmin
GBAS
3.00
PNW
2.50
2.00
1.50
1.00
0.50
0.00
oct
nov
dec
jan
feb
mar
apr
may
jun
jul
aug
sep
Detrended Temperature Driving Data for Flood Risk Experiments
Temperature
“Pivot 2003” Data Set
1915
“Pivot 1915” Data Set
2003
DJF Avg Temp (C)
Simulated Changes in the 20-year Flood
Associated with 20th Century Warming
DJF Avg Temp (C)
X20 2003 / X20 1915
X20 2003 / X20 1915
X20 2003 / X20 1915
Schematic of a Cool Climate Flood
Precipitation
Produces Snow
Precipitation
Produces Runoff
Precipitation
Produces Snow
Freezing Level
Snow Melt
Snow Melt
Precipitation
Produces Runoff
Precipitation
Produces Snow
Precipitation
Produces Snow
Schematic of a Warm Climate Flood
Freezing Level
2000
1996
1992
1988
1984
1980
1976
1972
1968
1964
1960
1956
1952
1948
1944
1940
CRB
1936
CA
1932
1928
3
1924
1920
1916
Std Anomalies Relative to 1961-1990
Regionally Averaged Cool Season Precipitation Anomalies
4
PNW
PRECIP
GB
2
1
0
-1
-2
-3
DJF Avg Temp (C)
20-year Flood for “1973-2003” Compared to “1916-2003” for a Constant
Late 20th Century Temperature Regime
X20 ’73-’03 / X20 ’16-’03
X20 ’73-’03 / X20 ’16-’03
Summary of Flooding Impacts
Rain Dominant Basins:
Increases in flooding due to increased precipitation
intensity, but no significant change from warming alone.
Mixed Rain and Snow Basins Along the Coast:
Strong increases due to warming and increased
precipitation intensity (both effects increase flood risk)
Inland Snowmelt Dominant Basins:
Relatively small overall changes because effects of
warming (decreased risks) and increased precipitation
intensity (increased risks) are typically in the opposite
directions.
Effects of ENSO and PDO
on Flood Risk
X100 wENSO / X100 2003
X100 nENSO / X100 2003
X100 cENSO / X100 2003
DJF Avg Temp (C)
DJF Avg Temp (C)
DJF Avg Temp (C)
X100 wENSO / X100 2003
X100 nENSO / X100 2003
X100 cENSO / X100 2003
X100 nPDO / X100 2003
X100 wPDO / X100 2003
X100 cPDO / X100 2003
DJF Avg Temp (C)
DJF Avg Temp (C)
DJF Avg Temp (C)
X100 wPDO / X100 2003
X100 nPDO / X100 2003
X100 cPDO / X100 2003
Scenarios of Flood Risk in
the 21th Century
21st Century Climate Impacts for the Pacific Northwest Region
Mote, P.W. and E. P. Salathe Jr., 2010: Future climate in the Pacific Northwest, Climatic
Change, DOI: 10.1007/s10584-010-9848-z
Seasonal Precipitation Changes for the Pacific Northwest
Mote, P.W. and E. P. Salathe Jr., 2010: Future climate in the Pacific Northwest, Climatic Change, DOI:
10.1007/s10584-010-9848-z
http://www.hydro.washington.edu/2860/
Columbia Basin Climate Change Scenarios Project
297 Sites
•Smaller basins down to
~500 km2
•Monthly and daily
streamflow time series
•Assessment of hydrologic
extremes
(e.g. Q100 and 7Q10)
Available PNW Scenarios
A1B
Emissions
Scenario
B1
Emissions
Scenario
2020s
10
9
2040s
10
9
2080s
10
9
19502098+
7
7
2020s
2040s
2080s
1
1
1
1
1
1
Downscaling Approach
Hybrid
Delta
Transient
BCSD
Delta
Method
hadcm
cnrm_cm
ccsm3
echam5
echo_g
cgcm3.1_t4
7 pcm1
miroc_3.2
ipsl_cm4
hadgem1
hadcm
cnrm_cm
ccsm3
echam5
echo_g
cgcm3.1_t4
7 pcm1
composite
of 10
2020s – mean 2010-2039; 2040s – mean 2030-2059; 2080s – mean 2070-2099
Hybrid Downscaling Method
• Performed for each VIC grid cell:
Hist. Daily
Timeseries
Projected Daily
Timeseries
1916-2006
Bias Corrected
Future
Monthly CDF
30 yr window
1916-2006
Hist. Monthly
Timeseries
Historic
Monthly CDF
1970-1999
1916-2006
“Base Case”
Spatial Variability of Temperature and Precipitation Changes
Monthly to Daily Precipitation Scaling
100
SeaTac. Feb, 1996, hypothetical 30% Increase
Daily Precipitation (mm)
90
80
hist
70
future
60
50
40
30
20
10
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Day of Month
Schematic of VIC Hydrologic Model
•
•
•
General Model Schematic
Sophisticated, fully distributed,
physically based hydrologic model
Widely used globally in climate
change applications
1/16 Degree Resolution
(~5km x 6km or ~ 3mi x 4mi)
Snow Model
Watershed Classifications:
Transformation From Snow to Rain
Map: Rob Norheim
Flood Analysis: What’s In? What’s Out?
Issue Affecting Analysis
Based on explicit daily
time step simulations of
streamflow?
Changing freezing
elevation?
Rain on snow captured?
Increases/decreases in
storm intensity?
Changes in tails of
probability distributions
affecting extreme daily
precipitation ?
Changes in size and
sequencing of storms?
Changes in small scale
thunder storms?
Includes water
management effects?
Yes
No
Yes
Yes
Yes
Yes (monthly statistics
only)
No
No
No
No
Low Flow Analysis: What’s In? What’s Out?
Issue Affecting Analysis
Based on explicit daily time
step simulations of
streamflow?
Effects of changing snowmelt
and soil moisture dynamics?
Effects of changing
evaporation?
Changes in sequencing or
duration of drought?
Includes shallow ground
water?
Yes
No
Yes
Yes
Yes, but some potential
factors omitted (e.g. changes
in cloudiness)
No
Includes deep groundwater?
No, but typically captures
relevant affects to low flows
anyway (well correlated)
No
Includes effects of glaciers?
No
Includes water management
effects?
No
Simulate Daily Time Step
Streamflow Scenarios
Associated with Changes
in Climate
Fit Probability Distributions
To Estimate Flood and Low Flow
Risks
Compare Flood
Risks to Those in the 20th Century
Probability of Exceedance
0.01
0.04
0.07
0.11
0.14
0.17
0.20
0.24
0.27
0.30
0.34
0.37
0.40
0.43
0.47
0.50
0.53
0.57
0.60
0.63
0.66
0.70
0.73
0.76
0.80
0.83
0.86
0.89
0.93
0.96
0.99
Streamflow (cfs)
120000
SNOMO
100000
80000
60000
HIST
ECHAM5_2040
40000
20000
0
2040s Changes in Flood Risk
Snohomish at Monroe
A1B
B1
Historical
10 Member Ensemble
Using the Hybrid Delta
Downscaling Approach
2040s Changes in 7Q10
Snohomish at Monroe
A1B
Historical
B1
10 Member Ensemble
Using the Hybrid Delta
Downscaling Approach
Chehalis at Grand Mound
Relationship Between Change in Q100 and Winter Temp
Changes in High Flows
Q100 values are projected to
systematically increase in many
areas of the PNW due to
increasing precipitation and
rising snowlines.
http://www.hydro.washington.edu/2860/products/sites/r7climate/study_report/CBCCSP
_chap7_extremes_final.pdf
Changes in Low Flows
7Q10 values are projected to
systematically decline in many
areas due to loss of snowpack
and projected dryer summers
http://www.hydro.washington.edu/2860/products/sites/r7climate/study_report/CBCCSP
_chap7_extremes_final.pdf
Current and Future Research
•Additional VIC calibration to improve simulations, and
comparison with DHSVM models (proposed)
•Estimate the effects of reservoir management using simulation
models (in progress)
•Optimized flood control operations to rebalance complex multiobjective reservoir systems
•Incorporate more realistic effects to extreme precipitation from
regional scale climate models (in progress)
•Incorporate the effects of sea level rise and high flows on
inundation using hydrodynamic modeling (proposed)
Regional Climate Modeling at CIG
 WRF Model (NOAH LSM) 36 to 12 km
 ECHAM5 forcing
 CCSM3 forcing (A1B and A2 scenarios)
 HadRM 25 km
 HadCM3 forcing
Extreme Precipitation
Change from 1970-2000 to 2030-2060 in the percentage of total precipitation
occurring when daily precipitation exceeds the 20th century 95th percentile
Salathé, E.P., L.R. Leung, Y. Qian, and Y. Zhang. 2010. Regional climate model projections for the State of
Washington. Climatic Change 102(1-2): 51-75, doi: 10.1007/s10584-010-9849-y
Snohomish River Near Monroe, WA

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