1. Climate Change and Water in the West Joe Casola, PhD Deputy Director, Climate Impacts Group University of Washington Healthy Headwaters October 16, 2015 Climate Science in the Public Interest

2. What have we seen? What do we expect? Substantial warming across the West, expected to continue Changes in precipitation vary among regions; natural variability likely to continue Reduced snowpack, shifts in streamflow timing Increases in heavy rainfall likely

3. Warming everywhere, all scenarios (2071-2099 vs. 1970-1999) Low emissions High emissions Source: National Climate Assessment, 2014

4. Warmer Stream Temperatures August Mean Surface Air Temperature and Maximum Stream Temperature Historical (1970-1999) 2040s medium (A1B) * Projections are compared with 1970-1999 average Mantua et al. 2010

5. Wetter in the Northwest; drier in the Southwest… But year-to- year variations still likely to dominate Source: National Climate Assessment, 2014

6. PacNW: Warming much greater than past variability, precip changes less detectable

7. Shifting Streamflows – Yakima Basin October April September Elsner et al. 2010

8. October April September Elsner et al. 2010 Increased: Flood risk, Landslide risk, Sediment flows Shifting Streamflows – Yakima Basin

9. October April September Elsner et al. 2010 Water needed for: irrigation, instream flows, fall hydro- production Warmer stream temperatures. Shifting Streamflows – Yakima Basin

10. Increased Risks for Heavy Rainfall, but Mechanisms Vary SOURCE: SW Climate Change Assessment Report http://www.swcarr.arizo na.edu/sites/default/file s/ACCSWUS_Ch7.pdf

11. Too little = exacerbation of existing water conflicts Too much = highlight risky land-use decisions “Indirect” impacts (fires, sediment flows) also matter Changes in streamflow will reshape the landscape Finding robust strategies –Goes beyond engineering –Will be iterative –Requires diverse engagement Too little water AND Too much water

12. 2015: Analog for the future PacNW - Temperatures looked like mid-21 st century; snowpack looked like end-of-century What are our sensitivities? What “broke?” Can we handle an extended version of this?

13. The Climate Impacts Group www.cses.washington.edu/cig Joe Casola jcasola@uw.edu