Quantifying Water Flux Changes in Evaporating Soils.

Soil water phase changes tightly couple water and energy budgets and impact the biological, chemical and physical processes occurring in the soil. However the understanding of the interplay of water and energy transfer associated with soil water phase changes are limited. Heat-pulse sensors have been demonstrated to accurately measure in situ soil water evaporation every 3 mm increment in the soil profile.  In this study, soil water phase changes will be quantified by determining both heat and water fluxes in evaporating soils in controlled column laboratory experiments. Combined with the measurement of soil temperature profile at very precise depth increments by using thermocouple sensors, heat-pulse sensors will be used to determine in situ evaporation rate and liquid water fluxes every 1-mm depth increment in the soil profile based on energy balance and water balance. Two soil textures (Hanlon sand and Ida silt loam), two primary surface boundary variables (humidity and radiation load), and one lower boundary variable (depth of water table) will be applied to the experiments. The results of the water phase changes will be evaluated from the distributions of measured soil temperature and thermal profile, and by the results simulated from a finite element approach.