Soil physical characteristics of shallow vadose zone and modeling its effects on upward capillary rise of groundwater in an arid-desert area.

Abstract

Two typical soil profiles of sand dune (mixed sandy loam with sandy soil; uniform sandy soil) were selected from the arid region on the edge of the Badain Jaran desert to analyze soil physical characteristics. The effects of soil physical characteristics on capillary rise were monitored and simulated. The relationship between two typical soil profiles of sand dune and capillary rise were investigated to reveal the interactive processes among groundwater, capillary water, and soil water. Results showed that capillary rise was mainly affected by soil bulk density and soil clay content in the arid-desert area. The capillary rise could reach to 152 cm above shallow layer in the profile of mixed sandy loam with sandy soils, and 120 cm in the profile of sandy soil, respectively. Soil water distribution driven by the capillary rise was more uniform in the profile of sandy soil. Soil water content showed a diminishing trend from the groundwater to the maximum distance of capillary rise. In contrast, soil water distribution was markedly varied in the profile of mixed sandy loam with sandy soil. The process of capillary movement could be well simulated with Hydrus-3D model. Soil structure above the groundwater was the critical factor, which could affect the capillary rise and soil water distribution. However, the effects of soil in-season evaporation and plant root uptake on capillary rise movement need to be explored in further studies.