Hydrologic response of Pacific Northwest Rivers to climate change

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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