1. Hydrologic response of Pacific Northwest Rivers to climate change
Fengge Su 1, Lan Cuo2, Huan Wu3, Nate Mantua1, Dennis P. Lettenmaier1
1University of Washington, Seattle, WA 98195
2University of Victoria, BC Canada V8W 2Y2
3 University of Montana, Missoula, MT 59812
Since you mention salmon in the next slide, you might include “salmon watersheds” in the title so people in the audience understand the orientation of this work
2018/12/2

2. Background North Pacific Rim 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.
North Pacific Rim
Pacific Ocean
Pacific Northwest
12/2/2018

3. Experimental Design
downscaled Climate data (T, P) for
Hydrologic model for streamflow simulations
Floodplain habitat model
Energy balance model for stream temperature simulations
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.
12/2/2018

4. Hydrology Model and dataset
Hydrology model: VIC
Study domain: shaded area
Resolution: 1/8
Number of grids:
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 (global, 0.5 degree) (Maurer et al. 2009; Adam and Lettenmaier 2003)
Output:
Daily runoff, soil moisture, evaporation, and snow water equivalent
Pacific Ocean
Pacific Northwest
12/2/2018

5. 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 degree,
with respect to observed climatology for the period at 2.0 degree
Bias correction
with respect to observed climatology for the period at 0.5 degree
Downscaling from 2.0 to 0.5 degree, monthly to daily
Regridding from 0.5 to degree
Using nearest neighbor approach

6. Bias correction: Quantile-Quantile technique with respect to observed climatology (1950-1999)
Bias corrected GCM value
Raw GCM value
Observed data cdf
Raw GCM cdf
Prcp CDF, monthly,2degree, grid data_47.00_121.00
Temp CDF, monthly,2degree,grid data_47.00_121.00

7. Monthly average precipitation ( ) from one GCM -BCCR (Bjerknes Centre for Climate Research in Norway)
Raw GCM output, 2.0 degree
bias corrected and downscaled map, 0.5 degree
mm/mon

8. Average of 20 GCMs bias-corrected temperature changes under Scenario A1B ºC ºC

9. Average of 20 GCMs bias-corrected precipitation changes under Scenario A1B
mm/mon
mm/mon

10. Hydrologic response to projected climate change -case study in Colombia River Basin
Resolution: 1/8 degree
Historic run:
Future run:
Salmon river
Willamette River
12/2/2018

11. Projected precipitation and temperature for the basins of Salmon and willamette
Precipitation (mm)
Temperature (ºC)
Are the historical averages shown with the red lines, and individual model projections shown with black lines?
For the temperature projections it is easier to see that the whole set of projections trends to warmer values for each month of the year … these are surface air temperature projections, and not water temperature projections, right?
Historical ( )
Single GCM
GCM average
12/2/2018

12. Projected streamflow for the basins of Salmon, and willamette
Single GCM
Willamette
GCM average
Historical ( )
Streamflow (m3/s)
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.
Doesn’t the Willamette Basin also have a substantial deep groundwater influence? How is that handled in the flow simulations?
12/2/2018

13. 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?
The other analysis that’s underway is the VIC hydrologic modeling simulations for North Pacific Rim watersheds …

14. Thank You!