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Impacts of the Real and Imaginary Components of Relative Permittivity on Time Domain Reflectometry Measurements in Soils

^a Crop Production, Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, Canada, K1A 0C6
^b Land and Water Commonwealth Scientific and Industrial Research Organization, G.P.O. Box 1666, Canberra, ACT 2601, Australia
^c Water Research Foundation of Australia, Centre for Resources and Environmental Studies, Australian National Univ., Canberra, ACT 2601, Australia

View larger version (26K): [in a new window]   Fig. 1 Schematic diagram of time domain reflectometry system (left), idealized trace (upper right), and voltage reflection pattern (lower right)

View larger version (11K): [in a new window]   Fig. 2 Time domain reflectometry trace showing the way in which travel time, t1, rise time, tr, of the return refelection were estimated for use in the calculations. This trace resulted from a 0.15-m-length probe in B horizon soil wetted with tap water

View larger version (31K): [in a new window]   Fig. 3 Relative permittivity as a function of water content. In (a) is the apparent relative permittivity estimated directly from time domain reflectometry based on Eq. 3. In (b) are the real (filled symbols) and imaginary (open symbols) components of the relative permittivity estimated from the use of Eq. [4] and [5]. In the legends, the first letter indicates the soil horizon (A or B), the next symbol(s) indicate the wetting solution (W = water, S1 = KCl solution once and S2 = KCl solution twice). The dotted curve was given by Topp et al. (1980). The solid curve assumes the water in soil has a relative permittivity of 80

View larger version (22K): [in a new window]   Fig. 4 Apparent relative permittivity, a, in relation to the real component, 'r, using more complete Eq. [4] and [5] for analysis of the time domain reflectometry traces: (a) = Temora A horizon; (b) = Temora B horizon. In the legends, the first letter indicates the soil horizon (A or B), the next symbol(s) indicate the wetting solution (W = water, S1 = KCl solution once, and S2 = KCl solution twice). The lines are 1:1

View larger version (25K): [in a new window]   Fig. 5 A comparison of electrical conductivity measurements by time domain reflectometry and conductivity bridge. YZT values are given by Eq. [8] and GT values result from Eq. [10]. In the legend, A and B refer to horizons of Temora soil. W refers to soil wetted with tap water. S refers to soil wetted with 0.05 M KCl solution. Filled symbols are GT, and open symbols are the corresponding YZT values

View larger version (21K): [in a new window]   Fig. 6 Giese-Tiemann (GT) electrical conductivity vs. the conductivity bridge measurement for the Temora soil. The line is 1:1. In the legend, A and B refer to horizons of Temora soil. W refers to soil wetted with tap water. S refers to soil wetted with 0.05 M KCl solution