Alan F. Hamlet JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering
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Transcript of Alan F. Hamlet JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering
Alan F. Hamlet
• JISAO/CSES Climate Impacts Group• Dept. of Civil and Environmental Engineering
University of Washington
Quantifying the Effects of Climate Variability and Change on Hydrologic Extremes in the Pacific Northwest
CBCCSP Research Team
Lara Whitely BinderPablo CarrascoJeff DeemsMarketa McGuire ElsnerAlan F. HamletCarrie LeeSe-Yeun LeeDennis P. LettenmaierJeremy LittellGuillaume MaugerNate MantuaEd MilesKristian MickelsonPhilip W. MoteRob NorheimErin RogersEric SalathéAmy SnoverIngrid TohverAndy 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.
Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molniahttp://nsidc.org/data/glacier_photo/special_high_res.html
Aug, 13, 1941 Aug, 31, 2004
The Myth of Stationarity Meets the Death of Stationarity
Muir Glacier in Alaska
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
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)
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)
Modeling Studies of Changing 20th Century Flood Risk in the West
Snow Model
Schematic of VIC Hydrologic Model• 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)
General Model Schematic
Avg WY Date of Flooding VIC
Avg
WY
Dat
e of
Flo
odin
g O
BS
Ln (X
100 /
Xm
ean)
OB
S
Ln (X100 / Xmean) VIC
Evaluating the Hydrologic Model Simulations in the Context of Reproducing Flood Characteristics
Red = PNW, Blue = CA, Green = Colo, Black = GB
Zp
X10
0 GEV
floo
d/m
ean
flood
Red = VICBlue = OBS
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20-yr
10-yr
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near
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CA
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ar T
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(Deg
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CA
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PNWTmin
Tmax
PNW
CACRB
GB
Regionally Averaged Temperature Trends Over the Western U.S. 1916-2003
Tem
pera
ture
Historic temperature trend
in each calendar month
1915 2003
Detrended Temperature Driving Data for Flood Risk Experiments
“Pivot 2003” Data Set
“Pivot 1915” Data Set
X20 2003 / X20 1915
DJF
Avg
Tem
p (C
)
DJF
Avg
Tem
p (C
)
Simulated Changes in the 20-year Flood Associated with 20th Century Warming
X20 2003 / X20 1915 X20 2003 / X20 1915
Freezing Level
SnowSnow
Schematic of a Cool Climate Flood
Precipitation Produces Snow
Precipitation Produces Snow
Precipitation Produces Runoff
Snow Melt
Freezing Level
SnowSnow
Schematic of a Warm Climate Flood
Pre
cipi
tatio
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rodu
ces
Sno
w
Pre
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Sno
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Precipitation Produces Runoff
Snow Melt
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Std
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ies
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PNWCACRBGB
Regionally Averaged Cool Season Precipitation Anomalies
PRECIP
DJF
Avg
Tem
p (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 ImpactsRain 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
DJF
Avg
Tem
p (C
)
DJF
Avg
Tem
p (C
)
DJF
Avg
Tem
p (C
)
X100 nENSO / X100 2003 X100 cENSO / X100 2003X100 wENSO / X100 2003
X100 nENSO / X100 2003 X100 cENSO / X100 2003X100 wENSO / X100 2003
DJF
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Tem
p (C
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DJF
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DJF
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Tem
p (C
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X100 nPDO / X100 2003 X100 cPDO / X100 2003X100 wPDO / X100 2003
X100 nPDO / X100 2003 X100 cPDO / X100 2003X100 wPDO / X100 2003
Scenarios of Flood Risk in the 21th Century
Mote, P.W. and E. P. Salathe Jr., 2010: Future climate in the Pacific Northwest, Climatic Change, DOI: 10.1007/s10584-010-9848-z
21st Century Climate Impacts for the Pacific Northwest Region
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
Spatial Variability of Temperature and Precipitation Changes
http://www.hydro.washington.edu/2860/
• Smaller basins down to ~500 km2
• Monthly and daily streamflow time series
• Assessment of hydrologic extremes
(e.g. Q100 and 7Q10)
Columbia Basin Climate Change Scenarios Project
297 Sites
Available PNW Scenarios
2020s – mean 2010-2039; 2040s – mean 2030-2059; 2080s – mean 2070-2099
Downscaling ApproachA1B
Emissions Scenario
B1 Emissions Scenario
Hybrid Delta
hadcm cnrm_cm ccsm3 echam5 echo_g cgcm3.1_t47 pcm1 miroc_3.2 ipsl_cm4 hadgem1
2020s 10 9
2040s 10 9
2080s 10 9
Transient BCSD
hadcm cnrm_cm ccsm3 echam5 echo_g cgcm3.1_t47 pcm1
1950-2098+ 7 7
Delta Method
composite of 10
2020s 1 12040s 1 12080s 1 1
Hybrid Downscaling Method
• Performed for each VIC grid cell:
Hist. DailyTimeseries
Hist. MonthlyTimeseries
Historic Monthly CDF
Bias CorrectedFuture
Monthly CDF
Projected DailyTimeseries
1916-2006
1970-1999
30 yr window
1916-2006
1916-2006“Base Case”
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 28 290
10
20
30
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hist
future
Dai
ly P
reci
pita
tion
(mm
)
Day of Month
Monthly to Daily Precipitation ScalingSeaTac. Feb, 1996, hypothetical 30% Increase
Snow Model
Schematic of VIC Hydrologic Model• 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)
General Model Schematic
Watershed Classifications:Transformation From Snow to Rain
Map: Rob Norheim
Flood Analysis: What’s In? What’s Out?Issue Affecting Analysis Yes No
Based on explicit daily time step simulations of streamflow?
Yes
Changing freezing elevation?
Yes
Rain on snow captured? YesIncreases/decreases in storm intensity?
Yes (monthly statistics only)
Changes in tails of probability distributions affecting extreme daily precipitation ?
No
Changes in size and sequencing of storms?
No
Changes in small scale thunder storms?
No
Includes water management effects?
No
Low Flow Analysis: What’s In? What’s Out?Issue Affecting Analysis Yes No
Based on explicit daily time step simulations of streamflow?
Yes
Effects of changing snowmelt and soil moisture dynamics?
Yes
Effects of changing evaporation?
Yes, but some potential factors omitted (e.g. changes in cloudiness)
Changes in sequencing or duration of drought?
No
Includes shallow ground water?
No, but typically captures relevant affects to low flows anyway (well correlated)
Includes deep groundwater? No
Includes effects of glaciers? No
Includes water management effects?
No
Simulate Daily Time Step Streamflow Scenarios
Associated with Changesin Climate
Fit Probability Distributions To Estimate Flood and Low Flow
Risks
Compare FloodRisks to Those in the 20th Century
0.99
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HISTECHAM5_2040
SNOMO
Stre
amflo
w (c
fs)
Probability of Exceedance
2040s Changes in Flood RiskSnohomish at Monroe
A1B B1
Historical10 Member Ensemble Using the Hybrid Delta Downscaling Approach
A1B B1
2040s Changes in 7Q10Snohomish at Monroe
Historical10 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
7Q10 values are projected to systematically decline in many areas due to loss of snowpack and projected dryer summers
Changes in Low Flows
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 (in progress)
• Estimate the effects of reservoir management using simulation models (in progress in selected basins)
• Optimized flood control operations to rebalance complex multi-objective reservoir systems (ongoing)
• 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
Comparison of Daily Peak Flow Estimates from Statistically and Dynamically Downscaled Climate Projections (1971-1999)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
50,000
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rcm
trans
Pea
k A
nnua
l Flo
w (c
fs)
Probability of Exceedance
Statistically Downscaled with Resampled Historical Daily Extremes
Dynamically Downscaled
Skagit River at Mount Vernon
Conclusions:
• Our initial exploration of changing flood risk in the PNW in response to projected regional warming and increases in cool season precipitation points to increasing flood risk in most areas of the region. Increases in flood risk are particularly large in those parts of the region which are a few degrees below freezing in winter.
• Due to projected warming, resulting loss of snowpack, and reductions in summer precipitation, the risks of extreme low flows are expected to increase in most areas of the PNW.
• Regional climate models offer more physically based assessment tools for understanding the implications of changing precipitation extremes, and may provide an improved picture of the spatial variations in changing hydrologic extremes.