Coupled Heat and Water Movement in Wettable and Hydrophobic Soils.

The presence of thermal gradients in soil can cause water to flow in the liquid and vapor phases.  Soil water repellency is a widespread phenomenon that can have implications on soil water flow.  The effect of soil wettability on soil water redistribution and soil thermal properties due to imposed temperature gradients is a topic that has not been extensively studied.  A closed column experiment was performed to evaluate coupled heat and water movement in wettable and non-wettable soils.  The objective of this experiment was to compare soil water redistribution and soil thermal properties for wettable and non-wettable soils with differing electrical conductivities in response to imposed temperature gradients.  Two wettable soils (silt loam and sand) to which three conditions (hydrophilic,hydrophobic-large EC, and hydrophobic small EC) were applied resulted in a total of six treatments.  Transient soil water content and temperature distributions were obtained through the use of Thermo-TDR probes installed at various depths within the soil columns.  Different boundary temperature gradients were also applied to the closed soil columns.  This experiment allows for comparison of the effect of soil wettability on water redistribution in closed soil columns with the same initial conditions and similar boundary conditions.