Abstract:

In desert and semidesert areas, vapor movement is often an important part of the total flux since it controls the partitioning of available energy into latent and sensible heat fluxes into the atmosphere. In addition, biological processes such as soil microbial activity and plant growth depend on the moisture and temperature status in the vadose zone, which are mainly influenced by the vapor movement. An experiment, in which the hourly measurements of water vapor flux in the vadose zone were reported, was conducted in a sandfilled bunker at a field site. It was found that the soil moisture reached the daily maximum value (5961  cm3/cm3 at 10 cm and 119131 cm3/cm3 at 30 cm) and minimum value (4445 cm3/cm3 at 10 cm and 104108 cm3/cm3 at 30 cm) at midday (12:0013:00 for 10 cm and 14:0015:00 for 30 cm) and before dawn (02:0003:00 for 10 cm and 04:0005:00 for 30 cm), respectively. The modified HYDRUS1D code, which refers to the coupled water, vapor and heat transport in soil, was used to develop a deeper understanding of the physical processes of soil water dynamics in this experiment. The numerical analyses provided insight into the diurnal movement of liquid water and water vapor driven by the gradients of pressure heads and temperatures in the subsurface zone. The simulated temperature and water content were in good agreement with the measured values. The spatialtemporal distribution of liquid water flux, of water vapor flux and of soil temperature showed a detailed diurnal pattern of soil water dynamics in relatively coarse sand.

Key words:

Key words: vadose zone; soil water dynamics; coupled water, vapor and heat transport