Alan F. Hamlet JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering University of Washington Effects of Projected Climate Change on the Hydrology of the Puget Sound Region and Potential Impacts to Puget Sound

Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia Aug, 13, 1941Aug, 31, 2004 Recession of the Muir Glacier

1) Modeling experiments reproduce history of global temperatures remarkably well. 2) Natural forcings (e.g. volcanic eruptions and variations in solar radiation) alone cannot explain the rapid rise in temperature at the end of the 20 th century.

Global Climate Change Scenarios for the PNW

Mote, P.W. and E. P. Salathe Jr., 2010: Future climate in the Pacific Northwest, Climatic Change, DOI: /s z 21 st Century Climate Impacts for the Pacific Northwest Region

Seasonal Precipitation Changes for the Pacific Northwest

Projected sea level rise in Puget Sound relative to ?

Hydrologic Projections

Hydrologic Products Draft

Snow Model Schematic of VIC Hydrologic Model and Energy Balance Snow Model

Watershed Classifications: Transformation From Snow to Rain Map: Rob Norheim

Effects to Rain Dominant Basins: Chehalis River near Grand Mound

SWERunoff

Mixed Rain and Snow (Warm): Nisqually River at La Grande Dam

SWERunoff

Mixed Rain and Snow (Colder): Snohomish River Near Monroe

Mild Snowmelt-Dominant Basins: Skagit at Mount Vernon

SWERunoff

HumanHealth Human Health Agriculture/Economics Salmon Forest Resources CoastsEnergy Infrastructure Water Resources A comprehensive climate change impacts assessment for Washington State Adaptation

Washington State Climate Change Impacts Assessment Executive Summary:

Changes in Hydrologic Extremes

Summary of Flooding Impacts Rain Dominant Basins: Possible increases in flooding due to increased precipitation intensity, but no significant change from warming alone. Mixed Rain and Snow Basins Along the Coast: Strong increases due to warming and increased precipitation intensity (both effects increase flood risk) Inland Snowmelt Dominant Basins: Relatively small overall changes because effects of warming (decreased risks) and increased precipitation intensity (increased risks) are in the opposite directions.

2040s Changes in Flood Risk Skagit River at Mount Vernon A1B B1 Historical 10 Member Ensemble Using the Hybrid Delta Downscaling Approach

Recession of Whitechuck Glacier (Sauk Headwaters) Photos courtesy of Dr. Mauri Pelto, Nichols College

Mass Balance of the Nisqually Glacier

Loss of glacial mass may maintain or even increase summer flow in the short term but is expected to decrease summer flow in the long term.

Year Annual area (ha × 10 6 ) affected by MPB in BC Bark Beetle Outbreak in British Columbia (Figure courtesy Allen Carroll)

Sediment Transport

Sediment Impact Pathways: Increasing precipitation intensity may increase the severity of extreme events (e.g. mud slides, inundation of public access areas, etc.) Loss of glaciers may mobilize large “reservoirs” of sediment stored beneath them. Loss of snowpack may reduce the “armoring” effect of the snowpack in moderate elevation areas, leading to increased land slide risk and increased sediment loadings. (conversion of moderate elevation areas from avalanche risk to land slide risk). Changes in forest disturbance patterns, particularly fire, may be important driver of impacts.

Sediment Impacts in the Nisqually Headwaters

Effects to Stream Temperature Mantua, N., I. Tohver, A.F. Hamlet, 2010: Climate change impacts on streamflow extremes and summertime stream temperature and their possible consequences for freshwater salmon habitat in Washington State, Climatic Change, online first, doi: /s

7Q10 values are projected to systematically decline in western WA due to loss of snowpack and projected dryer summers Changes in Low Flows Mantua, N., I. Tohver, A.F. Hamlet, 2010: Climate change impacts on streamflow extremes and summertime stream temperature and their possible consequences for freshwater salmon habitat in Washington State, Climatic Change, doi: /s

Nicholls, R. J. and Cazenave, A. (2010) Sea-Level Rise and Its Impact on Coastal Zones. Science 328, Sea Level Rise

Anticipate changes. Accept that the future climate will be substantially different than the past. Use scenario based planning over long time scales to evaluate options rather than the historical record. Expect surprises and plan for flexibility and robustness in the face of uncertain changes rather than counting on one approach. Plan for the long haul. Where possible, make adaptive responses and agreements “self tending” to avoid repetitive costs of intervention as impacts increase over time. Approaches to Adaptation and Planning