1. Alan F. Hamlet Philip W. Mote Dennis P. Lettenmaier JISAO Center for Science in the Earth System Climate Impacts Group and Department of Civil and Environmental Engineering University of Washington Sept, 2005 Impacts of Climate Change on the Columbia River Basin http://www.hydro.washington.edu/Lettenmaier/Presentations/2005/hamlet_climate_change_columbia_basin_2005.ppt

2. Hydroclimatology of the Pacific Northwest

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

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

5. 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 Sensitivity of Snowmelt and Transient Rivers to Changes in Temperature and Precipitation

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

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

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

9. April 1 SWE (mm) Current Climate“2020s” (+1.7 C)“2040s” (+ 2.5 C) -44%-58% Changes in Simulated April 1 Snowpack for the Cascade Range in Washington and Oregon

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

11. Comparison of simulated natural streamflow at Grand Coulee Dam for “1915 climate”, “2003 climate”, and a projected climate 2° C warmer than the baseline “2000 climate”. (The plot shows the effects of temperature changes alone—daily precipitation is identical in each case.)

12. Changes in Natural Streamflow for the “Middle of the Road” Scenarios Current Climate--Blue 2020s--Green 2040s--Red Impacts in the upper basin (Canada) are delayed in comparison with the lower basin (USA).

13. Effects of streamflow timing shifts and precipitation changes on drought frequency in the Okanogan Basin (Plot shows frequency of April-July flows below 1 million acre-ft in the Similkameen River at Nighthawk)

14. Effects of Hydrologic Changes Increased Winter Flow Increases winter flooding in some basins Increased scouring events and sediment loads(?) Potential benefits to winter hydro production Reduced Snowpack and Earlier Snow Melt Reduces spring flooding in some basins Reduces summer water availability (limited storage) Reduces summer hydro production May change structure of mountain ecosystems Longer dry season may intensify forest disturbance (e.g. fire, disease, insects) Late summer streamflows systematically lower (which may be intensified by shrinking glaciers) Increased water temperatures (?)

15. Decadal Climate Variability and Climate Change

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

17. Natural Streamflows at Dworshak Sustainable management of PNW water resources will very likely have to cope with flow variability associated with both “warm and wet” and “warm and dry” scenarios at different times. Such conditions can be incorporated in planning as a test for sustainability though adverse periods, rates of recovery during favorable periods, etc. Warm PDO 2040 Cool PDO 2040

18. Water Resources Implications for the Columbia River Basin

19. Hydropower Production Annual hydropower resources will follow annual flow regimes, which are mostly strongly related to uncertain changes winter precipitation. We expect that these values will be higher or lower at different times in the future (as in the 20 th century). Summer electricity demand is expected to increase over time as customers in the PNW install more a/c equipment and warming increases the number of cooling degree days. Winter demand is expected to decrease somewhat. Shifts in the seasonal timing of hydropower production may be required to meet these changing demands (more use of storage in summer). In isolation, Columbia basin winter hydropower production is relatively robust to streamflow timing shifts, but winter hydro production will be affected by the need to mitigate impacts to other system objectives such as flood control and instream flow augmentation.

20. Irrigation Irrigation from Columbia River main stem projects will probably not be substantially affected by streamflow timing shifts. Temperature sensitive basins (e.g. the Okanogan and Yakima basins) will likely see reduced summer water supplies and increased conflicts between instream flow augmentation, water temperature control, and water supply. In isolation, the upper Snake River irrigation projects may see little reduction in summer water supply over the next 50 years or so unless winter precipitation systematically declines (high elevation snow fields). Considerable reservoir storage in this part of the basin can also largely compensate for the modest streamflow timing shifts expected. Increased conflicts between the need to maintain instream flow and water temperature regimes (Dworshak dam) in the lower basin and conjunctive management of surface and groundwater irrigation rights farther upstream are expected to follow warming in this basin.

21. 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. (see transboundary issues). Hydro storage Fish flow storage Managed Flow Augmentation

22. 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 Adaptation to climate change will require complex tradeoffs between ecosystem protection and hydropower operations

23. 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

24. Water Temperature Higher air temperatures and increased residence time in reservoirs due to summer streamflow reductions are likely to systematically increase water temperatures throughout the basin. In managed basins, stored cold water in reservoirs may be exhausted more rapidly than now, reducing the ability to mitigate high stream temperatures using releases from storage, particularly in late summer. Cold water storage at Dworshak dam is a particular concern since it is one of the few dams available to control stream temperatures in the lower Snake and is sited in a sensitive area.

25. 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. Over the next 50 years or so, 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. Currently only the first two objectives are formally recognized in coordination agreements between the U.S. and Canada. Long-range planning is needed to address these issues.

26. Impacts to Recreation and Tourism Loss of mountain snowpack causing shorter ski seasons and more rainy days during the ski season, particularly in moderate elevation areas: http://www.hydro.washington.edu/Lettenmaier/Presentations/ 2003/hamlet_poster_PACLIM_apr_2003.ppthttp://www.hydro.washington.edu/Lettenmaier/Presentations/ 2003/hamlet_poster_PACLIM_apr_2003.ppt Loss of forest cover due to fire, disease, or insect damage Impacts to the sport fishing industry, particularly impacts to cold water fish such as trout and salmon due to higher water temperatures in rivers and lakes.

27. Broad Strategies for Incorporating Climate Variability and Climate Change in Long-Term Planning Identify and Assess Climate Linkages Identify potential linkages between climate and resource management that could affect outcomes in the long term. What’s being left out? Are there future “deal breakers” in these omissions? (e.g. increasing water temperature, glaciers maintaining summer streamflow in the short term) Design for Robustness and Sustainability Use modeling studies to test preferred management alternatives for robustness in the face of climate variability represented by paleoclimatic studies, conventional observations, decadal variability, and future climate change projections. Identify Limits and Increase Response Capability Use estimates of uncertainties or “what if” scenarios to find the performance limits inherent in preferred management alternatives. How can response capability be increased? Expect Surprises and Design for Flexibility to Changing Conditions Design contingency planning into management guidelines to allow for ongoing adaptation to unexpected (or uncertain) conditions without recursive policy intervention.

28. 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