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A Physically Derived Water Content/Permittivity Calibration Model for Coarse-Textured, Layered Soils

^a Dep. of Plants, Soils and Biometeorology, Utah State Univ., Logan, UT 84322-4820
^b The Institute of Soil, Water and Environmental Sciences, (ARO) The Volcani Center, Bet Dagan 50250, Israel

View larger version (57K): [in a new window]   Fig. 1. (A) Dual plate probe used for vertically draining and wetting TDR measurements in partially saturated porous media. The sintered plastic porous membrane at bottom allows water suctions of up to about 70 cm. (B) Energy density (E2) (darker shade = higher density) is demonstrated on the right as a two-dimensional horizontal cross-section.

View larger version (21K): [in a new window]   Fig. 2. Permittivity data for two types of monosize glass spheres and quartz sand measured in the vertical orientation. The data are compared with the empirically fitted relationships from Topp et al. (1980) (Eq. [10] and [11]).

View larger version (26K): [in a new window]   Fig. 3. Comparison of Topp et al.'s (1980) (Eq. [10] and [11]) empirical calibrations for glass spheres and Rubicon Sandy loam with model predictions based on Eq. [9].

View larger version (30K): [in a new window]   Fig. 4. Permittivity for desaturating glass spheres and sand grains. The filled symbols give the two-phase predictions from the Maxwell-Ganett (1904) model for spheres (Eq. [2]). The lines give the predictions using Eq. [4] to calculate the saturated and dry two-phase permittivity values, which were input into Eq. [9] to calculate the effective permittivity.

View larger version (17K): [in a new window]   Fig. 5. Permittivity–water content relationships for two soils, Hyrum and Kidman. The solid line is the model prediction based on measured parameters used in Eq. [4] and [9].

View larger version (22K): [in a new window]   Fig. 6. Drying and wetting cycles for glass spheres (left) and quartz sand grains (right) modeled using a simple two-layer model (Eq. [9]) fitted according to the measured saturated and dry permittivity values. Right-hand diagram is for quartz sand, modeled again according to Eq. [9].