1. Alan F. Hamlet Andrew W. Wood Dennis P. Lettenmaier JISAO Center for Science in the Earth System Climate Impacts Group and Department of Civil and Environmental Engineering University of Washington November, 2003 Observed Climate and Streamflow Variability in the Sacramento, San Joaquin, and Colorado River Basins and Projections for the 21 st Century

2. Observed Trends in Basin Average Temperature and Precipitation in the Sacramento and San Joaquin River Basins (Water Year 1916-1997) Note: Data is adjusted for topographic variations, and corrections for spurious trends associated with heat island effects, station moves, instrumentation changes, different groupings of stations, etc. have been applied.

3. Observed Temperature Trends over the Sacramento San Joaquin Basin 1916-1997

4. Observed Precipitation Trends over the Sacramento San Joaquin Basin 1916-1997

5. Streamflow Reconstructions from the Paleoclimatic Record Thanks to: Hugo Hidalgo, Scripps Institution of Oceanography Dave Meko, Laboratory of Tree-Ring Research, University of Arizona Connie Woodhouse, Paleoclimatology Branch, NOAA National Climatic Data Center

6. Sacramento River Flow Reconstructed from Tree Rings (6-year running mean) Source: Meko et. al, 2001, J. Amer. Water Res. Association, 37(4) 1029-39 (Fig 5)

7. Sacramento and Upper Colorado Annual Flow Reconstructions Concurrent periods of low flow are indicated by pink bands Meko, D.M. and C.A. Woodhouse, in review. Tree-ring footprint of joint hydrologic drought in Sacramento and Upper Colorado river basins, western USA. Journal of Hydrology

8. Overview of Streamflow Reconstructions for Water Managers: http://www.ncdc.noaa.gov/paleo/streamflow/study.html Sacramento River Reconstructions: Meko, D.M., Therrell, M.D., Baisan, C.H., and Hughes, M.K., 2001, Sacramento River flow reconstructed to A.D. 869 from tree rings: J. of the American Water Resources Association, v. 37, no. 4, p. 1029-1040. Meko, D.M. and C.A. Woodhouse, in review. Tree-ring footprint of joint hydrologic drought in Sacramento and Upper Colorado river basins, western USA. Journal of Hydrology Colorado River Reconstructions: Water Resources Bulletin, 31(5) (Special Issue on climate variability and drought in the Colorado River Basin) Stockton, C.W. and Jacoby Jr., G.C. 1976. Long-term surface-water supply and streamflow trends in the Upper Colorado River Basin based on tree-ring analysis. Lake Powell Research Project Bulletin 18, Institute of Geophysics and Planetary Physics, University of California, Los Angeles.

9. Some Selected Results from the Accelerated Climate Prediction Initiative (ACPI)

10. Accelerated Climate Prediction Initiative (ACPI) – NCAR/DOE Parallel Climate Model (PCM) grid over western U.S. A hydrologic simulation model and a reservoir operations model were run in each portion of the domain. Both sensitivity and adaptive response capability were evaluated.

11. Bias Correction from NCDC observations from PCM historical runraw climate scenario bias-corrected climate scenario month m Note: future scenario temperature trend (relative to control run) removed before, and replaced after, bias-correction step.

12. Downscaling observed mean fields (1/8-1/4 degree) monthly PCM anomaly (T42) VIC-scale monthly simulation interpolated to VIC scale

14. Reductions in Pacific Northwest Snowpack for PCM Scenarios (low sensitivity) The Main Impact Pathway in the West: Loss of Snowpack.

15. Results for the Sacramento and San Joaquin Basins Van Rheenen, N.T., A.W. Wood, R.N. Palmer and D.P. Lettenmaier, 2004, Potential Implications of PCM Climate Change Scenarios for Sacramento - San Joaquin River Basin Hydrology and Water Resources, Climatic Change (accepted)

16. PCM Business-as-Usual scenarios California (Basin Average) control (2000-2048) historical (1950-99) BAU 3-run average

17. PCM Business-as-Usual Scenarios Snowpack Changes California April 1 SWE

18. PCM Business-As- Usual Mean Monthly Hydrographs Shasta Reservoir Inflows 1 month 12

19. Lake Shasta Storage: 4552 taf Sacramento River Basin Trinity Whiskeytown Shasta Oroville (SWP) Folsom Clear Creek American River Feather River Trinity River Sacramento River Dam Power Plant River Transfer Delta

20. Delta & San Joaquin R Basin Dam Power Plant River/Canal Transfer Eastman, Hensley, & Millerton New Don Pedro & McClure Delta New Hogan Pardee & Camanche Stanislaus River Tuolumne & Merced Rivers Delta Outflow Mokelumne River Calaveras River San Joaquin River Pardee/Camanche Reservoir Storage: 615 taf New Melones Res Storage: 2420 taf Don Pedro/McClure Storage: 3055 taf Millerton Lake Storage: 761 taf Sacramento-San Joaquin Delta Area: 1200 mi 2 Delta New Melones San Luis

22. Storage Decreases Sacramento Range: 5 - 10 % Mean: 8 % San Joaquin Range: 7 - 14 % Mean: 11 % Current Climate vs. Projected Climate

23. Hydropower Losses Central Valley Range: 3 - 18 % Mean: 9 % Sacramento System Range: 3 – 19 % Mean: 9% San Joaquin System Range: 16 – 63 % Mean: 28%

24. Results for Colorado River Basin Christensen, N.S., Wood, A.W., Voisin, N., Lettenmaier, D.P. and R.N. Palmer, 2004, Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin, Climatic Change, (accepted)

25. Period 1 2010-2039 Period 2 2040-2069 Period 3 2070-2098 hist. avg. ctrl. avg. PCM Projected Colorado R. Basin Termperature

26. hist. avg. ctrl. avg. PCM Projected Colorado R. Basin Precipitation Period 1 2010-2039 Period 2 2040-2069 Period 3 2070-2098

27. Changes to Seasonal Hydrograph Simulated Historic (1950-1999)Period 1 (2010-2039) Control (static 1995 climate)Period 2 (2040-2069) Period 3 (2070-2098)

28. Deliveries to Central Arizona Project & Los Angeles Metro. Water District 1 BCM = 810,832 acre-ft

29. Conclusions and Comparative Analysis 1) California system operation is dominated by water supply (mostly ag), the reliability of which would be reduced significantly by a combination of seasonality shifts and reduced (annual) volumes. Partial mitigation by altered operations is possible, but complicated by flood issues. 2) Colorado system is sensitive primarily to annual streamflow volumes. Low runoff ratio makes the system highly sensitive to modest changes in precipitation (in winter, esp, in headwaters). Sensitivity to altered operations is modest, and mitigation possibilities by increased storage are nil (even if otherwise feasible). 3) These potential impacts highlight the need for contingency planning to cope with reductions in water supply and flexible demand management strategies for the future.