HR: 17:45h
AN: B34B-08 INVITED     [Abstracts]
TI: Vadose Zone Water Balance for Great Basin Phreatophytes
AU: * Harrington, R F
EM: bharrington@inyowater.org
AF: Inyo County Water Department, 163 May St., Bishop, CA 93514 United States
AU: Steinwand, A L
EM: asteinwand@inyowater.org
AF: Inyo County Water Department, 163 May St., Bishop, CA 93514 United States
AU: Or, D
EM: dani@engr.uconn.edu
AF: University of Connecticut, Dept. of Civil and Enviromemtal Engineering 261 Glenbrook Rd., Storrs, CT 06269 United States
AB: In hydrologically closed basins of the western United States, snowmelt runoff from mountain uplands is discharged by evapotranspiration (ET) from groundwater discharge zones in the arid lower elevations. Such groundwater discharge zones support a variety of phreatophytic and aquatic ecosystems, and are frequently developed for groundwater extraction, potentially resulting in conflicts between groundwater development and groundwater-dependent ecosystems. This study evaluated the growing season and annual vadose-zone water balances in phreatophytic meadow and scrub communities using measurements of ET, soil water, and precipitation. Total growing season ET ranged from 53 to 646 mm among all sites and years. ET during the winter was small, averaging approximately 40 mm. Estimates of evaporation directly from the water table based on soil properties and nighttime ET measurements indicated this was a small component of the water balance. For alkali meadows with depth to water in the 1 to 3 m range, groundwater uptake accounted for 60-81% of the total ET. Shrub-dominated sites had lower cover and transpiration, and relied less on groundwater. Estimates of groundwater uptake at two sites of markedly different soil and vegetation characteristics were comparable to estimates derived from seasonal water table fluctuations and measured specific yield. Groundwater uptake was correlated with water table depth (r²=0.62) and leaf area index (r²=0.70), even though depth to water and vegetation cover was less correlated (r²=0.44). A slightly higher correlation exists between groundwater uptake per unit leaf area and depth to water (r²=0.73).
DE: 1818 Evapotranspiration
DE: 1829 Groundwater hydrology
DE: 1836 Hydrological cycles and budgets (1218, 1655)
DE: 1875 Vadose zone
SC: Biogeosciences [B]
MN: Fall Meeting 2005