HR: 0800h
AN: H21D-0745    [Abstracts]
TI: Measurement and Modeling of Soil Moisture Under Differing Evaporative Conditions
AU: * Vaughan, P J
EM: Peter.Vaughan@ars.usda.gov
AF: SJVASC, USDA-ARS, 9611 S Riverbend Ave, Parlier, CA 93648, United States
AU: Ayars, J E
EM: James.Ayars@ars.usda.gov
AF: SJVASC, USDA-ARS, 9611 S Riverbend Ave, Parlier, CA 93648, United States
AB: Two experiments that measured bare soil evaporation and soil moisture were performed in a weighing lysimeter located at Five Points, CA. After wetting the soil surface overnight, the evaporation rate was determined for natural conditions by the changes in mass of the lysimeter soil box during a 14-day period in August, 2007. Subsequently, solar radiation was blocked and the experiment was repeated for six days. In both experiments, hourly measurements of soil water content were made at eight depths (0.1-1.0 m) using a capacitance probe. In natural sunlight, variation of soil moisture indicated upward water flow due to capillary forces caused by soil surface evaporation. At night, water flowed downward due to gravity. This diurnal cycle did not occur when solar radiation was blocked. Numerical simulations of one-dimensional water flow in these two experiments provided an estimation of the depth variation of water content reduction due to evaporation.
DE: 1818 Evapotranspiration
DE: 1838 Infiltration
DE: 1842 Irrigation
DE: 1843 Land/atmosphere interactions (1218, 1631, 3322)
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2007 Fall Meeting