Diurnal pattern of the drying front in desert and its application for determining the effective infiltration

摘要

Located in western Inner Mongolia, the Badain Jaran Desert is the secondlargest desert in China and consists of a regular series of stablemegadunes, among which over 70 permanent lakes exist. The unexpected lakesin desert attracted research interests on exploring the hydrological processunder this particular landscape; however, a very few literatures exist onthe diurnal and spatial variation of the drying front in this area, which isthe main issue in the desert hydrological process to characterize themovement of water in soil. In order to understand the drying front in theBadain Jaran Desert, a field campaign was conducted by the observations ofsoil physical parameters and micrometeorological parameters. With the fielddata, the performance of a vadose zone soil water balance model, the HYDRUS,was verified and calibrated. Then, the HYDRUS was used to produce thespatial and temporal information of coupled water, water vapour and heattransport in sand to characterize the variation pattern of the drying frontbefore, during and after the rainfall. Finally, the deepest drying front wasapplied to determine the effective infiltration, which is defined as theamount of soil water captured by the sand beneath the deepest drying frontby infiltrating water of an incident rainfall event.