HR: 1330h
AN: H32A-0516    [PDF]
TI: Water Flux Estimation by Multi Functional Heat Pulse Probe for Variably Saturated Sandy Soil
AU: * Mori, Y
EM: yasushim@life.shimane-u.ac.jp
AF: Shimane University, 1060 Nishikawatsu, Matsue, 690-8504 Japan
AU: Mortensen, A P
EM: apm@geo.geol.ku.dk
AF: Geological Institute, Oster Voldgade 10, Copenhagen, 2100 Denmark
AU: Hopmans, J W
AF: University of California, Davis, One shields Ave., Davis, CA 95616 United States
AU: Kluitenberg, G J
EM: gjk@ksu.edu
AF: Kansas State University, 2004 Throckmorton Hall, Manhattan, KS 66506-5501 United States
AU: Inoue, M
EM: mainoue@alrc.tottori-u.ac.jp
AF: Arid Land Research Center, 1390 Hamasaka, Tottori, 680-0001 Japan
AB: A small multi-functional heat pulse probe (MFHPP) with 5 stainless tube that includes a heater, two vertically and two horizontally installed thermistors was developed for water flux density measurement. A heat pulse generated from heater tube was measured at thermistor tubes 6mm away from the heater. Vertically installed thermistor measurement was affected by water flow and the flux was estimated by analytical solution for heat conduction including convection. Volumetric heat capacity and thermal diffusivity were estimated at horizontally installed thermistor assuming effect of water flow was small. Parameter optimization was employed because parameters could be examined using many data points and are not affected by outliner or noise. Falling head hydraulic conductivity experiment and multi-step outflow experiment were conducted for saturated and unsaturated water flux estimation respectively. Results showed that volumetric water content calculated from volumetric heat capacity corresponded very well with gravitationally calculated water content for both static condition and transient flow ranging from 10-5 to 10-8 ms-1. Also thermal diffusivity corresponded well with the known thermal diffusivity. Saturated water flow was successfully estimated in the range from 6.5x10-7 to 1.7x10-4 ms-1. However, for unsaturated flow, estimation diverged systematically at lower than 10-6ms-1. This may be attribute to the resolution limit of thermistor measurement or uncertainty in thermal diffusivity measurement. As a whole, unlike traditional methods, this method does not require water potential and hydraulic conductivity measurements, but directly measures water flux at a single point. Moreover, water content and thermal diffusivity were substituted from horizontal measurement, thus required data were also obtained within the same volume. It is an advantage for field condition where water content or thermal properties are not always available.
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting