非饱和带对发生在地表—地下水之间的水量交换以及溶质运移起到关键的控制作用，发生在非饱和带中的渗流过程，本质上是水相和气相相互驱替的过程。深入理解非饱和带中的水/气运动过程，对于地下水水量和水质的管理以及可持续利用具有重要意义。文章通过室内二维砂箱实验，研究了排水吸水过程中，非饱和带含水量分布的变化特征。采用光透射法监测排水吸水循环过程中含水量的分布状况，发现由于孔隙尺度不稳定排水现象的存在，湿润锋附近排水过程中的含水量横向波动(0.145~0.175）要大于吸水过程（0.150~0.165）。含水量分布在排水过程和吸水过程之间的差异说明了孔隙尺度的一些常见过程能够对达西尺度下的水分运动过程造成影响，而不是在提升尺度的过程中被简单抵消掉。

The unsaturated zone, which is the link between the s urface water and groundwater, plays a key role in controlling water exchange and solute transport in the soils. Infiltration in the unsaturated zone is in essence a problem of twophase
(air and water) immiscible displacement. A deep understanding of the airwater displacement process in the unsaturated zone is of great significance for the management and sustainable use of groundwater. A s eries of drainageimbibition
experiments are carried out to study the watercontent distribution in the unsaturated zone. The light transmission method is used to monitor water content in the 2-dimensional sandbox during the drainageimbibition cycles. It is found that the lateral fluctuation of water content in the drainage process (0.145-0.175) is greater than that in the imbibition process (0.150-0.165) due to the existence of unstable drainage processes at the pore-scale. The difference of water content between drainage and imbibition means that the mechanism happened at pore-scales should also be affected by water movement at darcy-scales.