Soil-Water Movement in Response to Imposed Temperature Gradients
1969
Cassel, D. K. | Nielsen, D. R. | Biggar, J. W.
Redistribution of soil water within insulated, uniformly packed, horizontal samples of unsaturated Columbia fine sandy loam at several soil-water contents was studied in response to imposed temperature gradients ranging from 0.5 to 1.0C/cm. Soil bulk density and initial, transient, and final soil-water-content distributions were determined each 0.5-cm along the column by gamma-radiation attenuation. Initial, transient, and final soil temperature distributions were monitored by glass-encased thermistors at 2-cm intervals—both at the center and 0.3 cm from the column wall. Apparent thermal and isothermal soil-water diffusivity values were calculated using transient water content data. The observed net water flux was found to increase with decreasing water content throughout the 0.077–0.274 cm³/cm³ range. For Columbia soil at 0.077 cm³/cm³ the observed mean net water flux across 1-cm sections of the soil showed acceptable agreement with that predicted by the theory of Philip and deVries; Fick's law and the modified Taylor-Cary irreversible thermodynamic equation both underpredicted the observed fluxes.
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