1. Effects of Climate Variability and Change on the Columbia River Basin
Center for Science in the Earth System
Climate Impacts Group
and Department of Civil and Environmental Engineering
University of Washington
Feb, 2006
Alan F. Hamlet
Philip Mote
Dennis P. Lettenmaier

2. Hydroclimatology of the Pacific Northwest

3. Annual PNW Precipitation (mm)
Elevation (m)
The Dalles

4. (mm)
Winter
Precipitation
Summer
Precipitation

5. Hydrologic Characteristics of PNW Rivers

6. 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

7. Pacific Decadal Oscillation El Niño Southern Oscillation
A history of the PDO
A history of ENSO
warm
warm
cool

8. Effects of the PDO and ENSO on Columbia River
Summer Streamflows
PDO
Cool
Cool
Warm
Warm
high
high
low
low
Ocean Productivity

9. Long-Term Trends in Temperature, Precipitation, and Streamflow

10. Trends in Annual Streamflow at The Dalles from 1858-1998 are strongly downward.

11. The Dust Bowl was probably not the worst drought sequence
in the past 250 years
red = observed, blue = reconstructed
Source: Gedalof, Z., D.L. Peterson and Nathan J. Mantua. (in review). Columbia
River Flow and Drought Since Submitted to Journal of the American
Water Resources Association.

12. Precip Tmax PNW CA GB CRB Tmin Canada USA
Fig 1 Domain and time series of cool season precip tmax tmin
CRB
Tmin

13. Precipitation

14. Tmin

15. Trends in Winter (Oct-Mar) Precipitation and Temperature
Tmax
Tmin
1916-
2003
DJF Avg Temperature
Rel. Trend %/yr
Trend (°C/yr)
Trend (°C/yr)
1947-
2003
DJF Avg Temperature
Rel. Trend %/yr
Trend (°C/yr)
Trend (°C/yr)

16. 20th Century Trends in Hydrologic Variables

17. Schematic of VIC Hydrologic Model and Energy Balance Snow Model
PNW CA
CRB GB
Snow Model

18. Trends in April 1 SWE
Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P., 2005, Declining mountain snowpack in western North America, BAMS (in press)

19. Overall Trends in April 1 SWE from 1947-2003
DJF avg T (C)
Trend %/yr
Trend %/yr

20. Temperature Related Trends in April 1 SWE from 1947-2003
DJF avg T (C)
Trend %/yr
Trend %/yr

21. Precipitation Related Trends in April 1 SWE from 1947-2003
DJF avg T (C)
Trend %/yr
Trend %/yr

22. peak snowpack are towards earlier calendar dates
Trends in timing of
peak snowpack are towards earlier calendar dates
Timing of peak snowpack has been advancing in the past 82 years, with lowest elevations advancing the most (30-40 days in some parts of the Cascades). The melt season starts sooner, and snowmelt-driven runoff has been observed to be trending earlier as well.
Change in Date

23. spring flows rise and summer flows drop
As the West warms,
spring flows rise and summer flows drop
Stewart IT, Cayan DR, Dettinger MD, 2005: Changes toward earlier streamflow timing across western North America, J. Climate, 18 (8):
Spring snowmelt timing has advanced by days in most of the West, leading to increasing flow in March (blue circles) and decreasing flow in June (red circles), especially in the Pacific Northwest.

24. June March Trends in simulated fraction of annual runoff in each month
from (cells > 50 mm of SWE on April 1)
March
June
Relative Trend (% per year)

25. Trends in March Runoff
Trends in June Runoff
DJF Temp (°C)
DJF Temp (°C)
Trend %/yr
Trend %/yr

26. Global Climate Change Scenarios and Hydrologic Impacts for the PNW

27. Humans are altering atmospheric composition
Methane has increased 151%, nitrous oxide 17%, also greenhouse gases

28. The earth is warming -- abruptly
What it is: Average surface temperature year by year
3 main features:
warming to 1940
cooling
warming since 1970
causes of these are different
were generally warmer than the top dots shown (continuing warming trend)

29. Natural AND human influences explain the observations best.
Natural Climate Influence
Human Climate Influence
Red: observations of global average temperature
Grey: simulations with a climate model (huge computer program, like weather prediction model only run for hundreds of years)
Natural influence: volcanoes, solar variations – guesses before ~1970, better since then
Human influence: greenhouse gases, sulfate aerosols
it is possible to simulate the climate of the last 100 years, and the conclusion is that humans didn’t matter much before 1960 – the early warming and the cooling were largely natural, and the late-century warming was largely human-caused
All Climate Influences

30. Four Delta Method Climate Change Scenarios for the PNW
Somewhat wetter winters and perhaps somewhat dryer summers

31. Changes in Mean Temperature and Precipitation or Bias Corrected Output from GCMs
ColSim
Reservoir
Model
VIC
Hydrology Model

32. The warmest locations are most sensitive to warming
+4.5% winter precip

33. Changes in Simulated April 1 Snowpack for the Canadian and U. S
Changes in Simulated April 1 Snowpack for the Canadian and U.S. portions of the Columbia River basin
(% change relative to current climate)
Current Climate
“2020s” (+1.7 C)
“2040s” ( C)
-3.6%
-11.5%
-21.4%
-34.8%
April 1 SWE (mm)

34. Naturalized Flow for Historic and Global Warming Scenarios
Compared to Effects of Regulation at 1990 Level Development
Historic Naturalized Flow
Estimated Range of
Naturalized Flow
With 2040’s Warming
Regulated Flow

35. Frequency of Drought in the Columbia River Comparable to Water Year 1992
(data from )
x 4.7
x 2
x 1.3
x 1.3

36. Decadal Climate Variability and Climate Change

37. Will Global Warming be “Warm and
Wet” or “Warm and Dry”?
Answer: Probably BOTH!

38. Water Resources Implications for the Columbia River Basin

39. Impacts on Columbia Basin hydropower supplies
Winter and Spring: increased generation
Summer: decreased generation
Annual: total production will depend primarily on annual precipitation
(+2C, +6%)
(+2.3C, +5%)
(+2.9C, -4%)
NWPCC (2005)

40. Warming climate impacts on electricity demand
Reductions in winter heating demand
Small increases in summer air conditioning demand in the warmest parts of the region
From a variety of charts in an NWPCC report ( see Fig.15), the monthly electricity demand during the winter is ~25000 MW; during the summer it's more like MW. So, the changes in winter demand in this figure are probably a reduction ~10% (as a maximum). This jives with some of the graphs from Sailor (I attached one) that calculates the sensitivity of electricity consumption for a 2 degree C warming to be a little less than 10%.
NWPCC 2005

41. Managed Flow Augmentation
The flow needed to provide acceptable flow velocity for juvenile transport is frequently higher than natural flow, particularly in late summer (I.e. use of storage is required). Climate change increases the amount of storage required to meet flow targets.
Currently very little storage is allocated to fish in comparison with hydropower.
In a conflict between hydro or irrigation and fish flow, the current reservoir operating policies are designed to protect hydro and irrigation (fish flow storage allocation for main stem and Snake River flow targets is at the top of a shared reservoir storage pool)
The Columbia River Treaty does not provide explicitly for summer flow in the U.S. (transboundary issues). Compare with guaranteed winter releases associated with flood control.
Hydro storage
Fish flow storage

42. Adaptation to climate change will require complex tradeoffs between ecosystem protection and hydropower operations
Source: Payne, J.T., A.W. Wood, A.F. Hamlet, R.N. Palmer, and D.P. Lettenmaier, 2004, Mitigating the effects of climate change on the water resources of the Columbia River basin, Climatic Change, Vol. 62, Issue 1-3,

43. Flood Control vs. Refill
Maintaining an appropriate balance between flood protection and the reliability of reservoir refill is crucial to many water resources objectives in the Columbia Basin.
As streamflow timing shifts move peak flows earlier in the year, flood evacuation schedules may need to be revised both to protect against early season flooding and to begin refill earlier to capture the (smaller) spring freshet.
Model experiments (see Payne et al. 2004) have shown that moving flood evacuation two weeks to one month earlier in the year helps mitigate reductions in refill reliability associated with streamflow timing shifts.
Payne, J.T., A.W. Wood, A.F. Hamlet, R.N. Palmer, and D.P. Lettenmaier, 2004, Mitigating the effects of climate change on the water resources of the Columbia River basin, Climatic Change, Vol. 62, Issue 1-3,

44. Temperature thresholds for coldwater fish in freshwater
Warming temperatures will increasingly stress coldwater fish in the warmest parts of our region
A monthly average temperature of 68ºF (20ºC) has been used as an upper limit for resident cold water fish habitat, and is known to stress Pacific salmon during periods of freshwater migration, spawning, and rearing
+1.7 °C
+2.3 °C

45. Implications for Transboundary Agreements
Snowpack in the BC portion of the Columbia basin is much less sensitive to warming in comparison with portions of the basin in the U.S. and streamflow timing shifts will also be smaller in Canada.
As warming progresses, Canada will have an increasing fraction of the snowpack contributing to summer streamflow volumes in the Columbia basin.
These differing impacts in the two countries have the potential to “unbalance” the current coordination agreements, and will present serious challenges to meeting instream flows on the U.S. side.
Changes in flood control, hydropower production, and instream flow augmentation will all be needed.
Long-range planning is needed to address these issues.

46. Conclusions
Climate change will result in significant hydrologic changes in the Columbia River and its tributaries.
These changes will not be equally distributed throughout the region or between different water management objectives.
With hydrologic changes, there will come a need to “rebalance” the system to compensate for these different impacts in each sector.
This “rebalancing” will take time and will involve complex (and contentious) tradeoffs between different management objectives.
We have the tools that we need to begin planning for a warmer future.
We should begin to include climate information in planning now to reduce the severity of future impacts as much as possible.

47. Selected References and URL’s
Climate Impacts Group Website
White Papers, Agenda, Presentations for CIG 2001 Climate Change Workshop
Climate Change Streamflow Scenarios for Water Planning Studies
Northwest Power and Conservation Council Columbia Basin Hydropower Study
Refs on Climate Variability and Climate Change