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Alan F. Hamlet Philip W. Mote Nathan Mantua Dennis P. Lettenmaier

Effects of Climate Change on the Columbia River Basin’s Water Resources. JISAO Center for Science in the Earth System Climate Impacts Group and Department of Civil and Environmental Engineering University of Washington Nov, 2005. Alan F. Hamlet Philip W. Mote Nathan Mantua

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Alan F. Hamlet Philip W. Mote Nathan Mantua Dennis P. Lettenmaier

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  1. Effects of Climate Change on the Columbia River Basin’s Water Resources JISAO Center for Science in the Earth System Climate Impacts Group and Department of Civil and Environmental Engineering University of Washington Nov, 2005 Alan F. Hamlet Philip W. Mote Nathan Mantua Dennis P. Lettenmaier

  2. Natural AND human influences explain the observations of global warming best. Natural Climate Influence Human Climate Influence All Climate Influences

  3. Temperature trends (°F per century) since 1920 coolerwarmer 3.6°F 2.7°F 1.8°F 0.9°F

  4. Annual Precipitation (Western WA, OR, BC)

  5. Hydroclimatology of the Pacific Northwest

  6. Annual PNW Precipitation (mm) Columbia River Basin Useable Storage ~35 MAF ~50% of storage is in Canada ~Storage is 30% of annual flow Snowpack functions as a natural reservoir The Dalles Elevation (m)

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

  8. Warming Affects Streamflow Timing • Temperature warms, • precipitation unaltered: • Streamflow timing is altered • Annual volume may be somewhat lower due to increased ET Black: Obs Red: 2.3° C warming

  9. Precipitation Affects Streamflow Volume • Precipitation increases, • temperature unaltered: • Streamflow timing stays about the same • Annual volume is altered Black -- Obs Blue -- 9% increase in precip.

  10. Observed Hydrologic Changes

  11. Trends in April 1 SWE 1950-1997 Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P., 2005, Declining mountain snowpack in western North America, BAMS (in press)

  12. 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): 1136-1155

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

  14. Four Delta Method Climate Change Scenarios for the PNW ~ + 2.25 C ~ + 1.7 C Somewhat wetter winters and perhaps somewhat dryer summers

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

  16. The warmest locations are most sensitive to warming +2.3C, +4.5% winter precip

  17. 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” (+ 2.25 C) -3.6% -11.5% -21.4% -34.8% April 1 SWE (mm)

  18. 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

  19. Decadal Climate Variability and Climate Change

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

  21. Water Resources Implications for the Columbia River Basin

  22. 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)

  23. 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 NWPCC 2005

  24. 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, 233-256

  25. 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, 233-256

  26. 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 +2.3 °C +1.7 °C

  27. 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.

  28. 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.

  29. Selected References and URL’s Climate Impacts Group Website http://www.cses.washington.edu/cig/ White Papers, Agenda, Presentations for CIG 2001 Climate Change Workshop http://jisao.washington.edu/PNWimpacts/Workshops/Skamania2001/WP01_agenda.htm Climate Change Streamflow Scenarios for Water Planning Studies http://www.ce.washington.edu/~hamleaf/climate_change_streamflows/CR_cc.htm Northwest Power and Conservation Council Columbia Basin Hydropower Study http://www.nwppc.org/energy/powerplan/plan/Default.htm Refs on Climate Variability and Climate Change http://www.ce.washington.edu/~hamleaf/hamlet/publications.html

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