Drying front dynamics during the falling rate stage of evaporation from homogeneous sandy soil profiles

Abstract

Due to climate change, drylands worldwide have been suffering from extensive droughts and desertification. Finding innovative solutions requires a thorough understanding of the evaporation process dominant in such regions. The process is divided into three stages based on the actual evaporation rate. Previous studies confirmed the significance of Stage 2, the falling rate stage, in drylands. One of the process’s main controlling factors is the drying front, or the region separating the saturated and unsaturated zones. This paper studied the drying front’s spatial and temporal development during Stage 2 in sandy soil profiles that differ in the pore structure. The drying front was determined experimentally using 1-D homogenous drying column tests. Besides, a front depth determination method from the literature was adopted. Both methods showed an acceptable agreement with the front receding rate during Stage 2. Moreover, coarser sandy soils with narrow pore size distribution tend to have shallower front depths. However, during Stage 2, their drying front recedes faster into the soil profile. This study serves as a fundamental step towards evaluating the drying front during evaporation; It is believed to contribute to designing an environmental-friendly soil cover system used to maximize land water storage.