Water Fluxes through the Vadose Zone of An Onion Field.

The presence of temperature gradients in unsaturated soils may induce water fluxes in gas and liquid phase that can significantly contribute to the water and energy transport processes. The liquid flux is important and dominates the water movement during the irrigation event when the water content is close to saturation, while the vapor flux dominates during soil drying. Hydrus-1D was used to simulate coupled heat, water vapor, and liquid water transport through soil. Real-time TDR and thermocouple sensors were used to monitor soil water content and temperature at various depths. Meteorological data (precipitation, relative humidity, air temperature, wind speed, and solar radiation) were available on an hourly basis from the NM Climate Center. Numerical simulations using Hydrus-1D adequately simulated the coupled soil and energy budget for the study site. Preliminary simulations showed that an upper dry and a lower wet zone could be distinguished near surface and vapor flux was much higher in the layer closer to the surface.