HR: 11:05h
AN: GC32A-04    [Abstracts]
TI: Runoff Efficiency of Sierra Snowmelt: Evaporative Water Losses in Wet vs. Dry Years
AU: * Lundquist, J
EM: jdlund@u.washington.edu
AF: University of Washington, Civil and Env. Engineering Box 352700, Seattle, WA 98195, United States
AB: High altitude Sierra basins have negligible summer precipitation and very little groundwater storage, which makes them ideal laboratories for indirectly monitoring changes in evaporative losses between wet and dry years. Dry years have greater potential evapotranspiration, due to warmer June and July air temperatures, warmer summer water temperatures, greater solar radiation exposure, and longer growing seasons. However, dry years also have limited saturated surface areas as compared to wetter years, and thus actual evapotranspiration is much less than the potential in dry years. Assessing the balance of these factors is important in estimating the effect of warming temperatures and shrinking snowpacks on Sierra ecosystems. When spring and summer rain events are excluded from the analysis, the annual sum of basin snowmelt (calculated from 119 CA DWR snow pillows) minus the sum of March to October streamflow (calculated from USGS records at 10 high-elevation California river basins) indicates water losses from the basin. Assuming negligible groundwater storage from one year to the next, these water losses are a measure of evaporation and evapotranspiration (ET). Records from 1968 to 2005 show that the least amount of water is lost to ET in the wettest years, but the story for dry to normal years is more complicated. Conceptual models are used to test the sensitivity of annual ET to snow cover extent, length of summer season, moisture availability, basin elevation distribution, and air and water temperatures. Results are compared with observations.
UR: http://faculty.washington.edu/jdlund/home/
DE: 0740 Snowmelt
DE: 0764 Energy balance
DE: 1818 Evapotranspiration
DE: 1836 Hydrological cycles and budgets (1218, 1655)
DE: 1840 Hydrometeorology
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting