Alan F. Hamlet, Philip W. Mote, Dennis P. Lettenmaier JISAO/CSES Climate Impacts Group

1. Understanding the Effects of Climate Change on Water Resources in the Pacific Northwest • Alan F. Hamlet, • Philip W. Mote, • Dennis P. Lettenmaier • JISAO/CSES Climate Impacts Group • Dept. of Civil and Environmental Engineering • University of Washington

2. Recession of the Muir Glacier Aug, 13, 1941 Aug, 31, 2004 Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia http://nsidc.org/data/glacier_photo/special_high_res.html

3. Tmax Canada USA PNW CA GB Tmin CRB

4. 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, 86 (1): 39-49

5. 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

6. Projections for the Future Using Global Climate Models

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

8. +3.2°C °C +1.7°C +0.7°C 1.2-5.5°C 0.9-2.4°C 0.4-1.0°C Observed 20th century variability Pacific Northwest

9. % +6% +2% +1% Observed 20th century variability -1 to +3% -1 to +9% -2 to +21% Pacific Northwest

10. Hydroclimatology of the Pacific Northwest

11. Annual PNW Precipitation (mm) Winter climate in the mountains is the key driver of streamflow. Snowpack functions as a natural reservoir. Elevation (m)

12. Hydrologic Characteristics of PNW Rivers

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

14. 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

15. 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.

16. Hydrologic Impacts for the PNW

17. Schematic of VIC Hydrologic Model and Energy Balance Snow Model 6 km 1/16th Deg. PNW 6 km Snow Model

18. The warmest locations that accumulate snowpack are most sensitive to warming +2.3C, +6.8% winter precip

19. Simulated Changes in Natural Runoff Timing in the Naches River Basin Associated with 2 C Warming • Increased winter flow • Earlier and reduced peak flows • Reduced summer flow volume • Reduced late summer low flow

20. Rain Dominant Chehalis River

21. Warm Transient Snow Hoh River

22. Cooler Transient Snow Nooksack River

23. Snowmelt Dominant Skagit River

24. Changes in Simulated April 1 Snowpack for the Canadian and U.S. portions of the Columbia River basin (% change relative to current climate) 20th Century Climate “2040s” (+1.7 C) “2060s” (+ 2.25 C) -3.6% -11.5% -21.4% -34.8% April 1 SWE (mm)

25. Effects of Basin Winter Temperatures Northern Location (colder winter temperatures) Southern Location (warmer winter temperatures)

26. Decadal Climate Variability and Climate Change

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

28. Regionally Averaged Cool Season Precipitation Anomalies PRECIP

29. Impacts to the Columbia River Hydro System

30. 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)

31. 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

32. Climate change adaptation may involve complex tradeoffs between competing system objectives 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

33. Implications for Transboundary Water Management in the Columbia Basin • Climate change will result in significant hydrologic changes in the Columbia River and its tributaries. • 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 as the flow regime changes.

34. Implications for the Columbia River Treaty • The Columbia River Treaty is focused primarily on conjunctive hydropower and flood control operations. • Arguably the greatest shortcoming of the agreement in the context of climate change adaptation is that currently the CRT does not encompass tradeoffs between the full range of management concerns facing the US and Canada. • Of particular concern is the need to encompass the different (and often competing) ecosystem needs in Canada and the US. • Does the Columbia River Treaty have the flexibility and scope needed to adapt to the water resources challenges of the 21st Century?

35. Overview of Some Water Resources Impact Pathways

36. Water Supply and Demand • Changes in the seasonality water supply (e.g. reductions in summer) • Changes in water demand (e.g. increasing evaporation) • Changes in drought stress • Increasing conflicts between water supply and other uses and users of water • Energy Supply and Demand • Changes in the seasonality and quantity of hydropower resources • Changes in energy demand • Increasing conflicts between hydro and other uses and users of water • Instream Flow Augmentation • Changes in low flow risks • Changes in the need for releases from storage to reproduce existing streamflow regime. • Changes in water resources management related to water quality (e.g. to provide dilution flow or to control temperature)

37. Flood Control and Land Use Planning • Changes in flood risks • Changes in flood control evacuation and timing • Dam safety • Impacts in Estuaries • Impacts of sea level rise and changing flood risk on low lying areas (dikes and levies) • Impacts to ecosystem function • Changes in land use policy (coastal armoring, land ownership, FEMA maps) • Long-Term Planning, Water Resources Agreements, Water Law and Policy • Water allocation agreements in a non-stationary climate (e.g. water permitting) • Appropriateness of the historic streamflow record as a legal definition of climate variability • Need for new planning frameworks in a non-stationary climate • Transboundary implications for the Columbia Basin

38. Approaches to Adaptation and Planning • Anticipate changes. Accept that the future climate will be substantially different than the past. • Use scenario based planning to evaluate options rather than the historic record. • Expect surprises and plan for flexibility and robustness in the face of uncertain changes rather than counting on one approach. • Plan for the long haul. Where possible, make adaptive responses and agreements “self tending” to avoid repetitive costs of intervention as impacts increase over time.

39. Overview of Some Existing Climate Change Water Planning Studies • Seattle Water Supply (Wiley 2004) • White River Basin (Ball 2004) • Snohomish Basin (Battin et al. 2007) • Columbia Hydro System (Hamlet et al. 1999; Payne et al. 2004, NWPCC 2005) Ball, J. A. 2004. Impacts of climate change on the proposed Lake Tapps-White River water supply, M.S.C.E. thesis, Dept. of Civil and Environmental Engineering, College of Engineering, University of Washington, Seattle. Battin J., Wiley, M.W., Ruckelshaus, M.H., Palmer, R.N., Korb, E., Bartz, K.K., Imaki, H., 2007. Projected impacts of climate change on salmon habitat restoration, Proceedings of the National Academy of Sciences of the United States of America, 104 (16): 6720-6725 Hamlet, A. F. and D. P. Lettenmaier. 1999b. Effects of climate change on hydrology and water resources in the Columbia River Basin. Journal of the American Water Resources Association 35(6):1597-1623. 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 62:233-256. NW Power and Conservation Council, 2007, Effects of Climate Change on the Hydroelectric System, Appendix N to the NWPCC Fifth Power Plan, http://www.nwcouncil.org/energy/powerplan/plan/Default.htm Wiley, M. W. 2004. Analysis techniques to incorporate climate change information into Seattle's long range water supply planning. M.S.C.E. thesis, Dept. of Civil and Environmental Engineering, College of Engineering, University of Washington, Seattle.