1. Trends in Summer Low Flows in King County Rivers and Streams: How Low Will They Go? Curtis DeGasperi King County DNRP, WLRD Salish Sea Ecosystem Conference October 27, 2011

2. Human Impacts on Water Cycle Land cover change – Forest clearing/Development ~1880

3. Human Impacts on Water Cycle Water management – Surface water and groundwater extraction – Consumptive uses (Irrigation) – Septic vs Wastewater conveyance – Pipeline infiltration/exfiltration

4. Water Management Basin Water Resources Streamflow Water Supply System Wastewater Disposal Withdrawals ExportsImports Exports Return via septic system disposal Precipitation I & I Evaporation/ Transpiration

5. Climate Change Natural Seasonal and Decadal Variability Human-induced trends or shifts Source: Nate Mantua Joint Institute for the Study of the Atmosphere and Ocean (JISAO) Pacific Decadal Oscillation (PDO)

6. Another Low Flow Metric? Big Soos Creek (12112600) July – October 2007 July – October Base Flow

7. Swamp Creek Issaquah Creek Newaukum Creek

8. Issaquah Creek Jul-Oct Base Flow Sea-Tac Airport Annual Precipitation

9. Puget Sound Jul-Oct Base Flow Jul-Oct Base Flow Annual Precip PDO Warm (+PDO)Cool (-PDO) Mote, P.W., A.K. Snover, L. Whitely Binder, A.F. Hamlet, and N.J. Mantua, 2005: Uncertain Future: Climate change and its effects on Puget Sound - Foundation Document. CIG, JISAO, University of Washington. Seattle, WA. 37 p. http://cses.washington.edu/cig/outreach/files/psat1005.shtml http://cses.washington.edu/cig/outreach/files/psat1005.shtml

10. Puget Sound Jul-Oct Base Flow Jul-Oct Base Flow Annual Precip PDO Warm (+PDO)Cool (-PDO) Source: Nate Mantua Joint Institute for the Study of the Atmosphere and Ocean (JISAO)

11. Skykomish near Gold Bar Jul-Oct Base Flow

12. ~600 cfs (17 cms)

13. Snoqualmie near Snoqualmie Falls Jul-Oct Base Flow ~250 cfs (77.1 cms)

14. Issaquah Creek near mouth Jul-Oct Base Flow ~10 cfs (0.28 cms)

15. Issaquah Creek near mouth Jul-Oct Base Flow ~8 cfs (0.23 cms) Estimated Losses of 6.5 cfs Land Cover Change: -0.1 cfs Water Management: -6.4 cfs

16. Swamp Creek at Kenmore Jul-Oct Base Flow ~1 cfs (0.03 cms)

17. Swamp Creek at Kenmore Jul-Oct Base Flow ~1 cfs (0.03 cms) Estimated Gain of 2.0 cfs! Land Cover Change: -3.8 cfs Water Management: +5.8 cfs

18. Newaukum Creek at Mouth Jul-Oct Base Flow ~1 cfs ~4 cfs (0.11 cms) Estimated Loss of 2.7 cfs Land Cover Change: -0.6 cfs Water Management: -2.1 cfs

19. How Low Will They Go?

20. Skykomish near Gold Bar Jul-Oct Base Flow

21. Conclusions Decadal climate variation appears to have a strong influence on stream base flow Water management appears to have the potential to influence stream base flow under certain circumstances

22. Thought What are the biological consequences?

23. “You never miss your water till the well runs dry” QUESTIONS? Curtis DeGasperi King County Water and Land Resources (206) 684-1268 curtis.degasperi@kingcounty.gov

24. Tohver, I. and A. Hamlet. 2010. Chapter 7: Impacts of 21st century climate change on hydrologic extremes in the Pacific Northwest region of North America. Climate Impacts Group, University of Washington, Seattle, WA. http://www.hydro.washington.edu/2860/http://www.hydro.washington.edu/2860/ Low flow, 7Q10, values are projected to decrease (i.e. increasing low flow risk) most strongly in rain dominant and transient basins (Figure 7). This pattern is particularly prominent in the lower elevation basins of the eastern Cascades and the mid to lower elevation basins in the western Cascades and in the Olympic Peninsula and the lower elevations on the west slopes of the Rockies. These results support the hypothesis that the intensity of the low flows will rise with increasing temperatures and evapotranspiration, which reduces the soil water moisture and late summer baseflows.

25. Extinction is Not An Option. Statewide Strategy to Recover Salmon. Washington State Joint Natural Resources Cabinet, September 21, 1999. http://www.digitalarchives.wa.gov/governorlocke/gsro/strategy/strategy.htm

26. Thoughts What are the biological consequences? Well designed long-term gauging network Compilation and access to up-to-date water management data Good models to synthesize information and extrapolate to ungauged basins