1. Paleo-reconstruction of summer streamflow and seasonal uncertainties using the VIC hydrologic model Eric Lutz Alan Hamlet Jeremy Littell JISAO CSES Climate Impacts Group Civil and Environmental Engineering University of Washington Climate science in the public interest

2. Acknowledgments Funding NOAA CPO SARP (N. Mantua, J. Littell, A. Hamlet, C. Woodhouse) JISAO Contributors J. Deems ~ Meteorological data processing M. McGuire Elsner ~ VIC implementation P. Carrasco ~ Programming support G. Pederson (USGS) ~ Chronologies of the Northern Rockies Contributors of the International Tree-Ring Data Bank

3. Goals I. Reconstruct Seasonal Streamflow  Exploit PNW character: Summer Streamflow driven by Winter Precipitation  Use a physically based hydrologic model (VIC) Summer Streamflow ~ Winter PrecipitationYakima Basin r 2 = 0.65 r 2 = 0.73; w/o outlier (1934)

4. Goals I. Reconstruct Seasonal Streamflow  Exploit PNW character: Summer Streamflow driven by Winter Precipitation  Use a physically based hydrologic model (VIC) Summer Streamflow ~ Winter Precipitation r 2 = 0.65 r 2 = 0.73; w/o outlier (1934)

5. Goals II. Quantify Streamflow Uncertainty  Integrate historic meteorological variability into tree-ring based streamflow reconstruction  Develop a physically-based framework for assessing streamflow uncertainty caused by various factors (Land use change, vegetation dynamic, etc.)

6. Methods 1. Reconstruct cool season (October-March) precipitation from proxy relationships between historic meteorological data and tree-ring chronologies 2. Create an extended historic meteorological dataset that contains natural variability of the historic record combined with the winter precipitation estimates from the paleo reconstruction. 3. Reconstruct summer streamflow for the period 1600- 1981 by driving VIC hydrologic model with the extended historic meteorological datasets. 4. Demonstrate how summer streamflow may be systematically influenced by a climate-change scenario.

7. Tree-ring Reconstruction of Basin-Average Winter Precipitation Meteorological Record EOF/PCA, Regression Historic Record (1916-2006) Paleo Period (1600-1915) Reconstructed Basin-Average Winter Precipitation Dendrochronological Record (Tree-rings) 91 years of Basin-Average Winter Precipitation 91 years of Basin-Average Winter Precipitation Mean Prcp winter,paleo

8. Tree-ring Reconstruction of Basin-Average Winter Precipitation ‘1937’ ‘1953’ ‘1983’ ‘1933’ ‘1926’ Disaggregate onto multiple winter precipitation patterns  Ensemble of Extended Meteorological Forcings for VIC High Flow Pattern Low Flow Pattern Ave. Flow Pattern

9. Summer Streamflow Reconstruction Historic Period (VIC-generated) Historic Meteorological Pattern associated with Very high summer flow Very low summer flow Average summer flow

10. Summer Streamflow Reconstruction Paleo-Reconstruction (VIC-generated) Historic Meteorological Pattern associated with Very high summer flow Very low summer flow Average summer flow r 2 = 0.3

11. Dalles Streamflow observations (thin black) and long-term linear trend (bold black, p =0.005) compared with reconstructed streamflow (thin red) and long-term linear trend (bold red, p = 0.08).

12. Summer Streamflow Reconstruction Climate Change Scenario (VIC-generated) Historic Meteorological Pattern associated with Very high summer flow Very low summer flow Average summer flow

13. Summer Streamflow Reconstruction Climate Change Scenario (VIC-generated) Paleo Future Ave. Paleo Ave. Future

14. Appendix

15. Meteorological Record EOF/PCA, Regression Historic RecordPaleo Period Reconstructed Basin-Average Winter Precipitation Reconstructed Basin-Average Winter Precipitation Reconstructed Streamflow Dendrochronological Record (Tree-rings) Select met. ensemble, using macro-scale hydrological model & sensitivity analysis Select met. ensemble, using macro-scale hydrological model & sensitivity analysis Spatial & temporal re-distribution of cool-season precipitation Macro-scale hydrological model Met. Ensemble Extended Distributed Meteorological Data (perturbed independently for Climate Change scenario) Extended Distributed Meteorological Data (perturbed independently for Climate Change scenario)

16. Study Design Meteorological Record EOF/PCA, Regression Historic Record (1916-2006) Paleo Period (1600-1915) Reconstructed Basin-Average Winter Precipitation Reconstructed Streamflow Dendrochronological Record (Tree-rings) Winter Precipitation Sensitivity Analysis Winter Precipitation Sensitivity Analysis Spatial & temporal re-distribution of cool-season precipitation Macro-scale hydrological model (VIC) Met. Ensemble Representative of Historic Variability Met. Ensemble Representative of Historic Variability Extended Distributed Meteorological Data (perturbed independently for Climate Change scenario) Extended Distributed Meteorological Data (perturbed independently for Climate Change scenario)