Hydrologic Implications of Climate Change for Western North America and the Columbia River Basin Alan F. Hamlet, Philip W. Mote, Dennis P. Lettenmaier 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 and Hydrologic Impacts for the PNW
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.
+3.2 C +0.7 C +1.7 C 0.9-2.4 C 1.2-5.5 C 0.4-1.0 C Pacific Northwest C Observed 20th century variability
-1 to +3% +6% +1% +2% -1 to +9% -2 to +21% Pacific Northwest % Observed 20th century variability
Local changes in climate may be larger than regional changes, but are also inherently more uncertain, particularly for precipitation. Climatic Changes for BC Portion of the Columbia Basin
Will Global Warming be Warm and Wet or Warm and Dry? Answer: Probably BOTH! 450000 Natural Flow Columbia River at The Dalles 400000 350000 300000 250000 200000 150000 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Apr-Sept Flow (cfs)
Hydrologic Implications of Climate Change
Schematic of VIC Hydrologic Model and Energy Balance Snow Model Snow Model
The warmer locations are most sensitive to warming +2.3C, +6.8% winter precip 2060s
Changes in Simulated April 1 Snowpack for the Canadian and U.S. portions of the Columbia River basin (% change relative to current climate) 20 th Century Climate 2040s (+1.7 C) 2060s (+ 2.25 C) -3.6% -11.5% -21.4% -34.8% April 1 SWE (mm)
Simulated Changes in Natural Runoff Timing in the Naches River Basin Associated with 2 C Warming 120 100 80 60 40 20 Impacts: Increased winter flow Earlier and reduced peak flows Reduced summer flow volume Reduced late summer low flow 1950 plus2c Simulated Basin Avg Runoff (mm) 0 oct nov dec jan feb mar apr may jun jul aug sep
250 200 150 100 50 0 Chehalis River oct nov dec jan feb mar apr may jun jul aug sep 1950 plus2c Simulated Basin Avg Runoff (mm)
500 450 400 350 300 250 200 150 100 50 0 Hoh River oct nov dec jan feb mar apr may jun jul aug sep 1950 plus2c Simulated Basin Avg Runoff (mm)
200 180 160 140 120 100 80 60 40 20 0 Nooksack River oct nov dec jan feb mar apr may jun jul aug sep 1950 plus2c Simulated Basin Avg Runoff (mm)
Landscape Scale Ecosystem Impacts
9.0 2005 8.0 7.0 2004 6.0 5.0 4.0 2003 3.0 2.0 2002 1.0 2001 2000 1999 0 1910 1930 1950 1970 1990 2010 Year Bark Beetle Outbreak in British Columbia (Figure courtesy Allen Carroll) Annual area (ha 10 6 ) affected by MPB in BC Annual area (ha 10 6 ) affected by MPB in BC
Temperature thresholds for coldwater fish in freshwater Warming temperatures will increasingly stress coldwater fish in the warmest parts of our region A monthly average temperature of 68ºF (20ºC) has been used as an upper limit for resident cold water fish habitat, and is known to stress Pacific salmon during periods of freshwater migration, spawning, and rearing +1.7 C +2.3 C
Impact Pathways Associated with Climate Changes in water quantity and timing Reductions in summer flow and water supply Increases in drought frequency and severity Changes in hydrologic extremes Changing flood risk (up or down) Summer low flows (glacial losses) Changes in groundwater supplies Changes in water quality Increasing water temperature Changes in sediment loading (up or down) Changes in nutrient loadings (up or down) Changes in land cover via disturbance Forest fire Insects Disease Invasive species
Impact Pathways Associated with Climate Changes in the energy sector Hydropower Energy demand Changes in outdoor recreation Tourism Skiing Camping Boating Changes in engineering design standards Road construction Storm water systems Flood plain definitions Building design Land slide risks
Impact Pathways Associated with Climate Changes in transportation corridors Changing risk of flooding, avalanche or debris flows Sea level rise Coastal engineering Land use planning Human health risks Temperature and water-related health risks
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.