HR: 09:00h
AN: H21E-03    [Abstracts]
TI: An Overview of Advances in Water Content Sensing for Small Watersheds and Ecohydrological Studies
AU: * Robinson, D A
EM: darobinson@cc.usu.edu
AF: Utah State Utah State University, Plants, Soils and Biometerology Ag Science building, Logan, UT 84321 United States
AU: Chandler, D
EM: david.chandler@usu.edu
AF: Utah State Utah State University, Plants, Soils and Biometerology Ag Science building, Logan, UT 84321 United States
AU: Jones, S B
EM: scott.jones@usu.edu
AF: Utah State Utah State University, Plants, Soils and Biometerology Ag Science building, Logan, UT 84321 United States
AB: Water content sensors based on the determination of soil permittivity have become a standard method of determining soil water content. The real permittivity of a material relates to its ability to store electrical energy. The permittivity of free water is about 80 whereas air is 1, and most soil minerals are between 4.5 and 9. Therefore, the proportion of water in a composite material strongly influences the bulk permittivity. Sensors exploiting this offer high temporal resolution data that can be collected using a data logger. However, the quality of water content determination is sensor specific, this depends on both sensor quality and certain soil properties. Two main soil properties influence sensor water content determination, bulk soil electrical conductivity and soil dielectric dispersion. The former, largely due to soil salinity causes attenuation of most electromagnetic signals and leads to increasingly poor water content estimates for bulk soil electrical conductivities above 2 dS/m. Dielectric dispersion relates to the real permittivity of the material changing as a function of frequency. Dielectric dispersion occurs particularly in clay soils and can result in different calibrations for sensors operating at different frequencies. Both of these soil phenomena are impacted by soil temperature. Although these instruments are good for point measurements and for field arrays there is a need to obtain better spatial water content data. We have tried utilizing electromagnetic survey data of small watersheds to indicate zones of hydrological interest. In particular, we are interested in using this approach to rapidly appraise the spatial distribution of soil depth and soil moisture content in research watersheds, to guide sensor placement. An ultimate goal is to develop methods for improved spatial determination of water content at the small watershed scale.
UR: http://soilphysics.usu.edu
DE: 1800 HYDROLOGY
DE: 1866 Soil moisture
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2005 Joint Assembly