HR: 0800h
AN: H31D-0430    [Abstracts]
TI: Hygrometric Measurement of Soil Water Potential
AU: * Butler, C D
EM: Cbutler1@utk.edu
AF: University of Tennessee Biosystems Engineering & Environmental Science, 2506 E.J. Chapman Drive, Knoxville, TN 37996-4531 United States
AU: Tyner, J S
EM: jtyner@utk.edu
AF: University of Tennessee Biosystems Engineering & Environmental Science, 2506 E.J. Chapman Drive, Knoxville, TN 37996-4531 United States
AB: Knowledge of soil water potential as a function of water content is required to make unsaturated flow and transport predictions. Although numerous methods are available to measure soil water potential, they are largely difficult and time consuming procedures. The goal of the research is to develop a hygrometric method that will perform satisfactorily with minimal required hardware or technician time. The volume of a drop of saline water will change due to evaporation or condensation until its salinity, and hence osmotic potential, is equal to the water potential in the adjacent gas phase. This relationship is exploited by our method to measure soil moisture potential. To begin, a drop of KCl solution with known mass and KCL concentration is placed adjacent to a soil sample with known water content inside a hermetically sealed container. The mass of the KCl drop is recorded over time with an electronic balance. As thermodynamic equilibrium is achieved, the mass of water within the KCl drop changes until its osmotic potential is equal to the capillary potential of water within the soil sample. After the mass of the KCl drop reaches equilibrium, the KCl concentration is calculated, which enables direct determination of the water potential within the soil sample. Unlike transient hygrometric measurements of water potential using psychrometers, no calibration is required.
DE: 1899 General or miscellaneous
DE: 1818 Evapotranspiration
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting