1. Climate Change in the Pacific Northwest
and Implications for the Snake River Basin
JISAO Climate Impacts Group and the
Department of Civil Engineering
University of Washington
September, 2001
Alan F. Hamlet
Andy Wood
Dennis P. Lettenmaier

2. (mm)
Winter
Precipitation
Summer
Precipitation

3. Hydrologic Characteristics of PNW Rivers

4. Sensitivity of Snowmelt and Transient Rivers
to Changes in Temperature and Precipitation
Temperature warms,
precipitation unaltered:
Streamflow timing is altered
Annual volume stays about the same
Precipitation increases,
temperature unaltered:
Streamflow timing stays about the same
Annual volume is altered

5. Effect of 1992 Winter Climate on Two PNW Rivers
Cedar River
Western Cascades
(caused predominantly by
warm temperatures)
Columbia River
at The Dalles
(caused both by warm
temperatures and
decreased precipitation)

6. Changes in Mean Temperature and Precipitation from GCMs
ColSim
Reservoir
Model
VIC
Hydrology Model

7. Climate Change Scenarios 2020s

8. Climate Change Scenarios 2040s

9. The main impact: less snow
April 1
Columbia
Basin
Snow
Extent

10. Columbia River at The Dalles 2020s “Middle-of-the-Road” Scenario

11. Columbia River at The Dalles 2040s “Middle-of-the-Road” Scenario

12. Water Resources in the Columbia River Basin
System objectives affected by winter flows
Winter hydropower production (PNW demand)
System objectives affected by summer flows
Flood control
Summer hydropower production (California demand)
Irrigation
Instream flow for fish
Recreation

13. Simulated Reliability of Water Resources Objectives
for “Middle-of-the-Road” Scenarios

14. 1 Palisades
2 Milner
3 Oxbow
4 Ice Harbor
5 Kiona 5 4 3 1 2

15. Snake River at Palisades

16. Snake River at Milner

17. Snake River at Oxbow

18. Snake River at Ice Harbor

19. Climate Change Implications for the Snake River Basin
Considered in isolation, the upper basin is probably well protected against relatively small temperature related streamflow timing shifts, but is vulnerable to uncertain reductions in precipitation, and basinwide considerations.
Irrigation and summer streamflows in the lower basin are vulnerable to temperature related streamflow timing shifts and potential reductions in precipitation.
Upper basin storage and irrigation demand may be indirectly affected by expected reductions in summer streamflows in the lower basin and main stem of the Columbia, since limited reservoir storage in the lower basin (Dworshak) is available to maintain streamflows in the lower basin (e.g. at Lower Granite).
Maintaining water temperature at acceptable levels may also pose considerable challenges.