Hydrologic Implications of Climate Change for the Western U.S., Pacific Northwest, and Washington State Alan F. Hamlet JISAO/CSES Climate Impacts Group Dept. of Civil and Environmental Engineering University of Washington
Recession of the Muir Glacier Aug, 13, 1941 Aug, 31, 2004 Image Credit: National Snow and Ice Data Center, W. O. Field, B. F. Molnia http://nsidc.org/data/glacier_photo/special_high_res.html
Global Climate Change Scenarios for the PNW
Consensus Forecasts of Temperature and Precipitation Changes from IPCC AR4 GCMs
21 st Century Climate Impacts for the Pacific Northwest Region Mote, P.W. and E. P. Salathe Jr., 2009: Future climate in the Pacific Northwest (in review)
PDO Effects of the PDO and ENSO on Columbia River Summer Streamflows 450000 400000 Cool Warm Cool Warm 350000 300000 250000 200000 150000 1900 1910 1920 1930 1940 1950 Apr-Sept Flow (cfs) 1960 1970 1980 1990 2000 Red=warm ENSO Green=ENSO neutral Blue=cool ENSO
Snowpack
Schematic of VIC Hydrologic Model and Energy Balance Snow Model Snow Model
Trends in April 1 SWE 1950-1997 Mote P.W.,Hamlet A.F., Clark M.P., Lettenmaier D.P., 2005, Declining mountain snowpack in western North America, BAMS, 86 (1): 39-49
Plotting Areas of High Hydrologic Disturbance Elsner et al., 2009: Implications of 21st Century climate change for the hydrology of Washington State (in review)
Change in Long-Term Mean April 1 SWE in WA -29% -27% -44% -37% -65% -53% Elsner et al., 2009: Implications of 21st Century climate change for the hydrology of Washington State (in review)
Changes in Seasonal Streamflow Timing
Simulated Changes in Natural Runoff Timing in the Naches River Basin Associated with 2 C Warming 120 Simulated Basin Avg Runoff (mm) 100 80 60 40 20 Impacts: Increased winter flow Earlier and reduced peak flows Reduced summer flow volume Reduced late summer low flow 1950 plus2c 0 oct nov dec jan feb mar apr may jun jul aug sep
Projected Streamflow Timing Shifts in Washington
Historical and Projected 21 st Century Flows for the A1b Scenario Simulated Natural Flows (cfs) 6000 5000 4000 3000 2000 1000 0 historical 2020A1b 2040A1b 2080A1b Chehalis River oct nov dec jan feb mar apr may jun jul aug sep
Historical and Projected 21 st Century Flows for the A1b Scenario 6000 historical Simulated Natural Flows (cfs) 5000 4000 3000 2000 1000 Quinault River 2020A1b 2040A1b 2080A1b 0 oct nov dec jan feb mar apr may jun jul aug sep
Historical and Projected 21 st Century Flows for the A1b Scenario 3500 historical Simulated Natural Flows (cfs) 3000 2500 2000 1500 1000 500 Elwah River 2020A1b 2040A1b 2080A1b 0 oct nov dec jan feb mar apr may jun jul aug sep
Historical and Projected 21 st Century Flows for the A1b Scenario 35000 historical Simulated Natural Flows (cfs) 30000 25000 20000 15000 10000 5000 Skagit River 2020A1b 2040A1b 2080A1b 0 oct nov dec jan feb mar apr may jun jul aug sep
Historical and Projected 21 st Century Flows for the A1b Scenario 12000 historical Simulated Natural Flows (cfs) 10000 8000 6000 4000 2000 Yakima River 2020A1b 2040A1b 2080A1b 0 oct nov dec jan feb mar apr may jun jul aug sep
Climate Change Will Result in Widespread Transformation of Snowmelt and Transient Watersheds to Rain Dominant Watersheds Mantua, N., I. Tohver, A.F. Hamlet, 2009: Impacts of climate change on key aspects of freshwater salmon habitat in Washington State, (in review)
Changes in Hydrologic Extremes
Simulated Changes in the 20-year Flood Associated with 20 th Century Warming X 20 2003 / X 20 1915 DJF Avg Temp (C) DJF Avg Temp (C) X 20 2003 / X 20 1915 X 20 2003 / X 20 1915
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.
Future Projections of Flood Risk in Washington Floods in western WA are expected to increase in magnitude due to the combined effects of warming and increasingly intense winter storms. Mantua, N., I. Tohver, A.F. Hamlet, 2009: Impacts of climate change on key aspects of freshwater salmon habitat in Washington State, (in review) In other parts of the State, changes in flooding are smaller, and in eastern WA projected reductions in flood risk are common due to loss of spring snow cover.
Changes in Low Flow Risks 7Q10 values are projected to systematically decline in western WA due to loss of snowpack and projected dryer summers Mantua, N., I. Tohver, A.F. Hamlet, 2009: Impacts of climate change on key aspects of freshwater salmon habitat in Washington State, (in review)
Landscape Scale Disturbance
9.0 2005 Annual area (ha 10 6 ) affected by MPB in BC 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0 1910 1930 1950 1970 1990 2010 Year 2004 2003 2002 2001 2000 1999 Bark Beetle Outbreak in British Columbia (Figure courtesy Allen Carroll)
Wide-Spread Glacial Retreat has Accompanied 20 th Century Warming. 1902 2002 The recession of the Illecillewaet Glacier at Rogers Pass between 1902 and 2002. Photographs courtesy of the Whyte Museum of the Canadian Rockies & Dr. Henry Vaux.
Loss of glacial mass may increase summer flow in the short term and decrease summer flow in the long term.
Warming Air Temperatures will Increase Water Temperature Mantua, N., I. Tohver, A.F. Hamlet, 2009: Impacts of climate change on key aspects of freshwater salmon habitat in Washington State, (in review)
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 fine sediments 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.
Adaptation
Approaches to Adaptation and Planning Anticipate changes. Accept that the future climate will be substantially different than the past. Use scenario based planning to evaluate options rather than the historic 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.