1. Impacts of hydrological variability and change on water resources Dennis P. Lettenmaier Department of Civil and Environmental Engineering University of Washington for presentation at Fifth IHP/IAHS George Kovacs Colloquium UNESCO, Paris 2 June 2000

2. Outline of this talk

3. Modeling the Connections Between Climate and Streamflow

4. Currently Modeled US Basins 1 Northwest5 Rio Grande10 Upper Mississippi 2 California6 Missouri11 Lower Mississippi 3 Great Basin7 Arkansas-Red12 Ohio 4 Colorado8 Gulf13 East Coast 9 Great Lakes

5. Long-Lead Climate Forecast ENSO PDO Run Initialized Hydrologic Model Ensemble Streamflow Forecast Select Met Data Ensemble from Historic Record Associated with Forecast Climate Category Schematic for Forecasting Experiments Using Resampled Observed Data

6. PDO/ENSO Effects Columbia PDO EffectsColumbia ENSO Effects

7. PDO/ENSO Effects Chester Morse PDO EffectsChester Morse ENSO Effects

8. Time Line for 12-month Lead Time Retrospective Forecasts Climate Forecast Estimated Initial Conditions Forecast Ensemble Lead time = 12 months

9. Columbia River Streamflow Forecast at The Dalles for 2001 Highest Simulation (1948-1997) Lowest Simulation (1948-1997) Cool PDO/ENSO Neut. Ensemble

10. Cool PDO/Cool ENSO Ensemble Columbia River Streamflow Forecast at The Dalles for 2000

11. Global Climate Models Regional Climate Models Hydrology Models Water Resources Models Overview of Streamflow Forecasting Schemes Using Climate Models water demand streamflow Temp. Precip. wind downscaling

12. Oct Nov May DecFebMarApr JunJul... Repeating 1960 Observed Temp and Precip Time Series with Nov-April Replaced by MM5 Forecasts MM5 Sim Constructing the Hydrology Model Driving Data Using a Normal SST Nov-Apr Climate Forecast MM5 Sim 24 MM5 Forecasts... Jan 1960

13. Control (observed Nov-Apr’s) RCM (raw climate simulations for Nov-Apr’s) Test Simulations for the Columbia River at The Dalles

14. Mean Variance Simple Bias Correction Used in MM5 Experiments (Nov-Mar Ensembles inserted in repeating 1960)

15. Quantile Mapping Bias Correction

16. Mean Variance Kanawha River Basin Simulations Using Observed Data and Bias Corrected GCM Output Observations Bias-Corrected GCM

17. Downscaled GSM forecast ensembles compared to historical climatological bounds

18. 1 Ohio 3 Delaware 4 Alabama-Coosa-Tallapoosa 2 Potomac 5 Apalachicola-Chattahoochee-Flint Current Streamflow Forecast Basins

20. Climate Scenarios Transient GCM Simulations for Increasing CO2 and Aerosols Adjustments To Observed Meteorology Delta Precip, Temp Hydrologic Model (VIC) Natural Streamflow Reservoir Model (ColSim) DamReleases, Regulated Streamflow Performance Measures Reliability of System Objectives

21. 2025

22. 2045

23. ColSim Reliability of System Objectives