干旱区生态环境知识资源中心

In arid and semi-arid environments, soil profiles often exhibit a liquid - vapour displacement known as evaporation front characterised by a critical matric potential (psi(me)) or water content (theta(e)) located somewhere inside the unsaturated zone above a watertable ( WT). The objective of this study was to determine the theta(e) including the range of water content (theta) in the transition zone from liquid to vapour both theoretically and experimentally for different soil textures under saline and non-saline WTs. Characteristic shapes of water content and salt concentration profiles were the criteria to obtain. e experimentally, and the. - diffusivity relationship was used to compute the theta(e) and theta range in the transition zone. Measured theta(e) values of 0.05 and 0.12 m(3)/m(3) under non- saline WT and 0.07 and 0.15 m(3)/m(3) under saline WT were in agreement with the computed values of 0.05 and 0.10 m(3)/m(3) for sandy loam and clay loam soils, respectively. The model calculates roughly the same. e for saline and non- saline conditions. Besides experimental soils, theta(e) and range of theta in the transition zone were calculated for silty loam and coarse sand. The lighter the soil texture, the smaller is theta(e) and the steeper the transition zone. The results were further compared with those calculated by different authors.