1. Alan F. Hamlet Andy Wood Dennis P. Lettenmaier JISAO Climate Impacts Group and the Department of Civil Engineering University of Washington September, 2001 Hydroclimatology of the Pacific Northwest and Long-Lead Streamflow Forecasts for the Columbia River Basin for 2002

2. Geophysical Characteristics of the Columbia Basin Elevation (m) Avg Naturalized Flow The Dalles Flows Originating in Canada Milner

3. Effects of the PDO and ENSO on Columbia River Summer Streamflows Cool Warm

4. Naturalized Summer Streamflow at The Dalles

5. Snake at Milner ENSO Effects

6. Snake at Milner PDO Effects

7. Snake at Milner PDO/ENSO Effects

8. Naturalized Summer Streamflow at Milner

9. Overview of Long-Range Forecasting Methods and Long-Range Forecasts for Water Year 2002

10. Global Climate Models Regional Climate Models Hydrology Models Water Resources Models Overview of Modeling Linkages water demand streamflow temp precip wind downscaling Observed Meteor. Data

13. 1998 CC 4

14. 1999 CC 6

15. 2000 CC 6

16. 2001 CC 5

17. 2002 Forecast Construction Details: Hindcast hydrologic state for August 1, 2001 based on observed weather data VIC driving data from August 1- Sept 30 is taken from 15 observed water years from 1949-2000 associated with winter ENSO neutral conditions in the tropics. This produces 15 forecast ensembles from Oct, 2001 to September, 2002 Experimental Forecasts for 2002 Based on Resampled Observed Driving Data

18. Raw streamflow forecast ensemble at The Dalles compared to 50-year “observed” min, max and mean monthly simulated streamflow Observed Long Term Mean Highest Observed Lowest Observed

19. Summary of raw streamflow forecast ensemble compared to 50- year “observed” min, max and mean monthly simulated streamflow {whiskers show 90th and 10th percentiles of forecast} Natural Flow at The Dalles

20. 2002 Forecast Construction Details: Hindcast hydrologic state for August 1, 2001 based on observed weather data VIC driving data from September 1- February 28 are taken from 20 climate global climate model simulations. VIC driving data from March 1- September 30 are based on median 1953 meteorological data This produces 20 forecast ensembles from Oct, 2001 to September, 2002 Experimental Climate Model Driven Forecasts for 2002

21. Climate Model-Based 20-member streamflow forecast at The Dalles 1953 driving data for March-Sept

22. Summary of raw streamflow forecast ensemble compared to 50- year “observed” min, max and mean monthly simulated streamflow {whiskers show 90th and 10th percentiles of forecast}

23. Raw 2002 Streamflow Forecast at Ice Harbor Retrospective Resampling Technique

24. Summary of 2002 Streamflow Forecast at Ice Harbor Retrospective Resampling Technique

25. Conclusions: Typical relationships between categorical PDO/ENSO state and PNW winter climate can be exploited to produce useful long lead time streamflow forecasts for PNW rivers using several methods. The 2001 drought has produced unusually dry soil conditions in the Columbia River basin, and winter flows in 2002 are expected to be somewhat below average. Likely ENSO neutral conditions for winter 2002 are most likely to produce near normal summer streamflows at The Dalles. Flows at Ice Harbor are somewhat more variable in comparison to flows at The Dalles, but are also centered around mean flows.

26. Observed System Storage Sept 1 Observed System Storage April 1 Obs. 1977-1978 refill sequence full Forecast System Storage: Oct, 2001- Sept, 2002 Firm Energy is met in 3 out of 15 simulations (20% reliability) empty

27. Summary of System Storage Simulation {whiskers are 10th and 90th percentiles}

28. Ensemble Average Energy Shortfalls from ColSim Associated with Streamflow Forecast

29. Conclusions Drought conditions in 2001 will increase the likelihood of below average winter flows in 2002 due to reduced soil moistures. Current reservoir contents and limited summer refill in 2001 will produce high vulnerability to capacity-related hydro system shortfalls in winter 2002, and will likely also prevent complete reservoir refill in summer 2002. Normal “firm” energy production from the hydro system is shown to be about 20% reliable in the simulations, with most shortfalls occurring in Jan and Feb. Reservoir storage in spring 2002 will be comparable to spring 2001. Expected energy shortfalls (as compared to normal conditions) for winter 2002 are on the order of 850,000 MW-hrs.