Hydrologic response of Pacific Northwest Rivers to climate change
23/4/21
Fengge Su 1, Lan Cuo2, Huan Wu3, Nate Mantua1, Dennis P. Lettenmaier1
1University of Washington, Seattle, WA 981952University of Victoria, BC Canada V8W 2Y23 University of Montana, Missoula, MT 59812
A warming climate will alter:
• the snow pack
• seasonality of streamflow
•magnitude and frequency of
peak flow and low flow events
•Water temperatures
•Changes in hydrologic regime
and stream temperature have
the potential to negatively impact
the Pacific wild salmon.
04/21/23
Background
Pacific Northwest
North Pacific Rim
Pacific Ocean
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downscaled Climate data (T, P) for 2010-2098
Hydrologic model for streamflow simulations
Energy balance model for stream temperature
simulations
Floodplain habitat model
Experimental DesignExperimental Design
Statistically downscale coarse-resolution temperature and precipitation change scenarios from global climate models; use these as forcings in a finer scale hydrologic model to produce streamflow and temperature change scenarios.
Hydrology Model and dataset
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Input:
Daily precipitation, Tmax, Tmin, and Wind
speed.
Derived input: Downward Solar and long
wave, vapor pressure deficit
Observed meteorology: daily P, Tmax, Tmin,
Wind for 1950-1999 (global, 0.5 degree)
(Maurer et al. 2009; Adam and Lettenmaier 2003)
Output:
Daily runoff, soil moisture, evaporation, and
snow water equivalent
Hydrology model: VIC
Study domain: shaded area
Resolution: 1/8
Number of grids: 146351
Pacific Ocean
Pacific Northwest
Bias correction and spatial downscaling scheme for GCM output (Wood et al., 2002, 2004)
Raw monthly P &T from 20 GCMs in IPCC AR4 under scenarios B1, A1B at 0.5-3.5 degree, 2010-2098
Bias correction
Downscaling from 2.0 to 0.5 degree, monthly to daily
Regridding from 0.5 to 0.125 degree
with respect to observed climatology for the period 1950-1999 at 2.0 degree
with respect to observed climatology for the period 1950-1999 at 0.5 degree
Using nearest neighbor approach
Bias correction: Quantile-Quantile technique with respect to observed climatology (1950-1999)
Bias corrected GCM value
Raw GCM value
Observed data cdf
Prcp CDF, monthly,2degree,
grid data_47.00_121.00
Temp CDF, monthly,2degree,grid data_47.00_121.00
Raw GCM cdf
Monthly average precipitation (2070-2098) from one GCM -BCCR (Bjerknes Centre for Climate Research in Norway)
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Raw GCM output, 2.0 degree
bias corrected and downscaled map, 0.5 degree
mm/mon
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1960-1999
2040-2069
2070-2098
Average of 20 GCMs bias-corrected temperature changes under Scenario A1B
ºC
ºC
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Average of 20 GCMs bias-corrected precipitation changes under Scenario A1B
1960-1999
2040-2069
2070-2098
mm/mon
mm/mon
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Resolution: 1/81/8 degreeHistoric run: 1960-1999Future run: 2000-2098
Hydrologic response to projected climate change -case study in Colombia River Basin
Salmon riverWillamette River
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Projected precipitation and temperature for the basins of Salmon and willamette
Precip
itation (m
m)
Tem
peratu
re (ºC)
2010-2039 2010-2039
2040-2069 2040-2069
2070-2098 2070-2098
2010-2039
2040-2069
2040-2069
2070-2098
2070-2098
Salmon Willamette Salmon Willamette
2010-2039
Single GCM GCM averageHistorical
(1960-1999)
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11
12 1 2 3 4 5 6 7 8 9 10 11 12
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Projected streamflow for the basins of Salmon, and willamette
• The salmon is a snow-melt dominant basin, while Willamette is a rain dominant basin.
• The spring peak flow is projected to appear earlier in the Salmon basin in connection with an earlier snow melt.
• The Willamette basin is projected to have an increasing cool season flow as a result of increasing winter precipitation.
Stream
flow (m
3/s)
2010-2039 2010-2039
2040-2069
2040-2069
2070-2098
2070-2098
Salmon Willamette
GCM averageHistorical
(1960-1999)
Single GCM
1 2 3 4 5 6 7 8 9 10 11 12
1 2 3 4 5 6 7 8 9 10 11 12
Analysis underway …• see our POSTER on stream temperature simulations: Climate
Change impacts on the hydrology and temperature of Pacific Northwest streams (1340h H33E-0929, Wednesday )
• How will a changing climate affect summer low flows and flood peaks?
• How will a changing climate affect snow water equivalent (SWE) in Spring?
• How will a changing climate and hydrologic regime affect stream temperature?
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Thank You!
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