Impacts of Climate Change on the Tualatin River Basin

1. Impacts of Climate Change on the Tualatin River Basin Nathan VanRheenen, Erin Clancy, Richard Palmer, PhD, PE Dept. of Civil and Environmental Engineering University of Washington www.tag.washington.edu

2. Talk Overview • Background • Research Approach • Impacts on Meteorology • Impacts on Hydrology • Impacts on System Yield • Final Conclusions

4. Insight from a Notable American Philosopher The future ain't what it used to be. -Yogi Berra

5. It's time for those of us who work on climate change to help the public and policymakers understand the evidence: Climate change is real, well underway, and poses severe risks to the United States and the world. Dr. Peter Gleick Director, The Pacific Institute 2003 MacArthur Fellowship Award Winner

6. Translating the Challenge to Regional Analysis What are the likely impacts of climate change on regional watersheds? • Types of impacts • Magnitude of impacts • Mitigation responses • Case Studies • Seattle Water Department • Portland Water Bureau • Tualatin Basin

7. Setting • Rain-driven watershed (no snow impacts) • Multiple uses: M&I, Ag, Fish, Recreation • 500,000 customers (M&I) • Agriculturally productive • Water Quality Concerns (temperature) • Current system is fully allocated • M&I demands expected to increase 400% by 2050 • Ag demands, 50% by 2050 • System highly sensitive to changes in summer flows • System expansion is under consideration

9. General Circulation Models • Hydrology Model, EPA BASINS • Tualatin River Integrated Management System (TRIMS) Models for Evaluating Climate Change • Tualatin River Integrated Management System (TRIMS)

10. Impacts on Meteorology

11. Global climate models operate at a scale of 2-5° latitude • Global data must be downscaled to the local station scale in order to assess the impacts of climate change on water resources.

12. From Climate Signals to Runoff Historical Meteorology Climate Signals Predicted Meteorology Hydrology Model Predicted Runoff

13. Temperature Signals from GCMs

14. Precipitation Signals from GCMs

15. Impacts on Hydrology

16. Hydrology Model • EPA BASINS • Watershed and subwatershed delineation: ArcGIS add-on • Rainfall-runoff simulation: HSPF (Stanford Watershed Model) • Can be extended to model water quality • Calibrated to match monthly flows at six stations

17. BASINS Model Nodes

18. Impacts on Hydrology: Hagg Lake Inflows

19. Impacts on Hydrology: Summer Flows

20. Impacts on Water Resources System

21. Tualatin River Integrated Management System (TRIMS)

22. TRIMS Description • Dynamic model of the basin • Purpose: Calculate system yield • Incorporates • Major system features and operations • BASINS inflows • M&I and Ag water supply demands • Present, Contracted, 2050 • CWS environmental targets (Present, 2050) • Instream flow targets • Scoggins Dam expansion alternatives • Increase dam elevation by 20 ft, 40 ft

23. Hagg Lake Storage – Current System

24. Hagg Lake Storage – 40 ft Expansion

25. Hagg Lake Yield – Current System 40000 acre-ft/100 days = 130mgd 40000 acre-ft/150 days = 87 mgd

26. Hagg Lake Yield – Current System

27. Hagg Lake Yield – 20 ft Expansion

28. Hagg Lake Yield – 40 ft Expansion

29. Hagg Lake “Expansion Schedule”

30. Conclusion

31. Conclusion • Impacts on Temperature and Precipitation • Increase in temperature of 2-4 °F • Wetter winters, drier summers • Impacts on Streamflow • 10-20% lower flows in summer, wetter winters • Impacts on Yield • Decreases 1.5% per decade for current system and current demands

32. Conclusion • System Expansion without climate change • 97% reliable yield increased from 38,000 acre-ft per year to 60,000 acre-ft (20-ft expansion) and 73,000 acre-ft (40-ft expansion) • System Expansion with climate change by 2040 • Yield shifts downward by about 4,000 acre-ft • Climate change impacts suggest expansion needed 5-8 years earlier