Climate Change and Hydrology in the Sierra Nevada Lorrie Flint U.S. Geological Survey Sacramento CA
Discussion Topics Climate change for California Methods to evaluate hydrologic impacts Water balance modeling Downscaling projections Processes contributing to impacts Timing of springtime snowmelt Soil moisture Cold air pooling and refugia Climatic water deficit Changes in delivery mechanisms: recharge vs runoff Implications for land and resource management
Climate for California: current and future conditions 4 scenarios Precipitation, mm/yr 950 900 850 800 750 700 650 600 550 500 1900 1950 2000 2050 2100 Historical GFDL- A2 GFDL- B1 PCM- A2 PCM- B1 Maximum Air Temperature, C 27 26 25 24 23 22 21 1900 1950 2000 2050 2100 Historical GFDL- A2 GFDL- B1 PCM- A2 PCM- B1
Climate for California: Extremes Atmospheric Rivers!
Climate Change and Extremes
Translating climate change to hydrologic response Requires an approach to simulate hydrology from available information Basin Characterization Model (BCM) grid-based data uses climate data, soils, and geology to calculate potential evapotranspiration recharge and runoff actual ET climatic water deficit snow accumulation and snow melt
Sublimation Precipitation Solar radiation Snow accumulation Air temperature Potential evapotranspiration Snowmelt Watershed available water (excess water) Actual evapotranspiration Climatic water deficit (PET-AET) Recharge Basin discharge Runoff Groundwater recharge
Soil moisture storage from SSURGO soils
Impacts of a changing climate on hydrologic processes Soil moisture Snowpack and springtime runoff Changes in mechanisms for water delivery, partitioning recharge and runoff Cold-air pooling and refugia Climatic water deficit Demand estimates Landscape stress and resiliency
Soil water influences on water availability 120 0'0"W Available Soil Storage (mm) 0-50 50 100 100 150 150 200 200-300 300-400 400-1000 120 0'0"W
1998 April 1 st Soil Water Content 1977 120 0'0"W 120 0'0"W
April 1 st Snow Water Equivalent 120 0'0"W SWE lost to soils over melt season 120 0'0"W 1998 1998 Relative volume (mm) 120 0'0"W 120 0'0"W
April 1 st Snow Water Equivalent 120 0'0"W SWE lost to soils over melt season 120 0'0"W 1977 1977 Relative volume (mm) 120 0'0"W 120 0'0"W
Changes in April 1 st snowpack (SWE) Change from baseline (1951-1980) to current (1981-2010) Decreases due to warming at all but the highest elevations
Downscaling Climate Change Scenarios 12-km 0 25 50 100 Kilometers Data are spatially downscaled to 270-m using Gradient-Inverse- Distance-Squared interpolation for hydrologic model application For every month an equation is developed for every grid cell using northing, easting, and elevation to incorporate elevational and regional gradients 270-m SIERRA NEVADA OWENS VALLEY Maximum Air Temperature June 2035 (C) 11-20 20-23 23-26 26-28 28-30 30-32 32-35 35-37 37-40 40-47
Upper Tuolumne Basin GFDL A2 9 Minimum air temperature, degrees C 8 7 6 5 4 3 2 1 0 1895 1902 1909 1916 1923 1930 1937 1944 1951 1958 1965 1972 1979 1986 1993 2000 2007 2014 2021 2028 2035 2042 2049 2056 2063 2070 2077 2084 2091 2098 2500 2000 Precipitation, mm/yr 1500 1000 500 0 1895 1902 1909 1916 1923 1930 1937 1944 1951 1958 1965 1972 1979 1986 1993 2000 2007 2014 2021 2028 2035 2042 2049 2056 2063 2070 2077 2084 2091 2098
0 20,000 40,000 60,000 80,000 100,000 120,000 2000 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 2044 2048 2052 2056 2060 2064 2068 2072 2076 2080 Runoff, ac-ft August 0 200,000 400,000 600,000 800,000 1,000,000 1,200,000 1,400,000 1,600,000 2000 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 2044 2048 2052 2056 2060 2064 2068 2072 2076 2080 Runoff, ac-ft December 0 100,000 200,000 300,000 400,000 500,000 600,000 2000 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 2044 2048 2052 2056 2060 2064 2068 2072 2076 2080 Runoff, ac-ft June 0 200,000 400,000 600,000 800,000 1,000,000 1,200,000 1,400,000 2000 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 2044 2048 2052 2056 2060 2064 2068 2072 2076 2080 Runoff, ac-ft March Upper Tuolumne Basin Surface runoff contribution, no baseflow
120 0'0"W Changes in Recharge/Runoff Mechanisms How water is delivered to the system will change 40 0'0"N < -2-2 - -1-1 - 1 1-2 > 2 Rch/run increases Rch/run decreases 35 0'0"N Loss of snow cover increases recharge Higher peak flows and compressed wet season increase runoff where there is shallow soils or no snow cover Deep soils can maintain recharge processes with compressed season, higher peaks, and increasing aridity 120 0'0"W
Change in ratio of recharge to runoff (1981-2010) - (2071-2100) Change in ratio of recharge to runoff (1981-2010) (2071-2100) Upper Pit < -2-2 - -1-1 - 1 1-2 > 2 Rch/run increases Rch/run decreases 120 0'0"W Tuolumne American Merced 120 0'0"W
Snow data to assess cold-air pooling following Lundquist et al. 2008
No Cold Air Pooling With Cold Air Pooling -1.6 C 2001GA2jun <mm> 10-100 100-500 500-1,000
Projected changes in wolverine habitat for consideration of reintroduction to Sierra Nevada Used 8 scenarios of climate change, size of home ranges, and relationship between snowpack and fecundity Currently enough habitat to support 170 adult female home ranges declining to 70 by 2100 Depending on scenario Projections of increased habitat to 60% loss by mid-century 11% to 90% loss by end of century
Climatic Water Deficit Annual evaporative demand that exceeds available water Potential Actual Evapotranspiration Integrates climate, energy loading, drainage, and available soil moisture storage Vegetation independent (indicator) Address irrigation demand Generally increases with all future climate scenarios SUPPLY PET DEFICIT 2001 mm/yr <775 775-800 800-825 825-850 850-875 875-900 900-925 925-950 950-975 975-1000
Climatic Water Deficit
Summary GCM output provides projections of climate change for the next century Needs downscaling for effective application and translated to hydrologic response to provide impacts of the interrelated processes at landscape level Climate change impacts hydrology with local variations Impacts in the Sierra Nevada and implications for management Rising air temperatures and earlier and more variable springtime snowmelt More frequent summer droughts Uncertainties in runoff due to soil moisture Landscape stresses due to increasing CWD Species distributions, forest health, wildfire Fine scale representation offers potential refugia and connectivity