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Measuring Water Content in Saline Sands Using Impulse Time Domain Transmission Techniques

Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721

View larger version (11K): [in a new window]   Fig. 1. Schematic of measurement setup, showing connection of the transmission line in the column to the vector network analyzer (VNA).

View larger version (28K): [in a new window]   Fig. 2. Time domain separation of first arrivals with the transmission line immersed in air and in the variably saturated sand at specified average volumetric water contents and pore water electrical conductivity (w). The shaded regions in Fig. 2b represent the domains over which the gate is applied to the air (dark shading) and sand (light shading) signals.

View larger version (24K): [in a new window]   Fig. 3. Travel time as a function of water content for tap water (0.5 dS m-1) and three pore water electrical conductivity conditions (10, 25, and 40 dS m-1) calculated from the time separation of the first arrivals. The best fit for tap water is superimposed on the four plots.

View larger version (17K): [in a new window]   Fig. 4. Travel time as a function of frequency for tap water with the sand at four different water contents and a pore water electrical conductivity of 25 dS m-1 at one of the previously specified water contents calculated using the gated time domain method. The dotted vertical black line indicates the frequency at which further analyses were performed (0.75 GHz).

View larger version (17K): [in a new window]   Fig. 5. Travel time as a function of water content for pore water electrical conductivity of 5, 10, 15, 20, 25, and 40 dS m-1 calculated using both methods: the time separation of first arrival and the gated time domain transmission (TDT) method. The best fit for each method is shown (solid black line) along with the relationship suggested by Hook and Livingston (1996).