Numerical Analysis of Coupled Liquid Water, Water Vapor, and Heat Transport in a Sandy Loam Soil

摘要

Information on the coupled liquid water, water vapor and heat transport under arable field conditions is still limited, particularly in semi-arid unsaturated soils such as arid southern New Mexico. Hydrus-ID model was applied to evaluate various transport mechanisms associated with temporal variations in soil water content and soil temperature in the unsaturated zone of a sandy loam furrow-irrigated field located at Leyendecker Plant Science Research Center, Las Cruces. The model was calibrated and validated using measured soil water content and soil temperature in the sandy loam soil beds at four depths of 5,10, 20, and 50 cm for a 19-day period from day of the year (DOY) 85 (26 March 2009) through DOY 103 (April 13 2009) and a 31-day period from DOY 104 (April 14 2009) through DOY 134 (14 May 2009), respectively. Measured soil hydraulic and thermal properties, and daily meteorological data were used in model simulations. Simulated results with the field experiment demonstrated that the model predicted soil water content and soil temperature and their temporal variations at all depths adequately. The total liquid water flux (comprised of isothermal and thermal liquid water) dominated the soil water movement during and early periods of an irrigation event, while the contribution of total water vapor flux (comprised of primarily thermal and much smaller isothermal water vapor) increased with increasing soil drying before and after irrigation. During the progressively soil drying process, the upward isothermal and thermal liquid water fluxes within 15 cm depth also served as potential sources of liquid water, which eventually changed to water vapor near the surface. Water vapor flux was much higher in the layer near soil surface and was approximately 10.4% of the total coupled water flux during the simulation period.