The Mechanism of Water Movement in the Freezing-Thawing Process
冻结-冻融过程中水分运移机理

In order to understand the mechanism of water movement in the freezing-thawing process, the authors conducted simulation test and monitoring work for field soil water transport at different water table depths in the northern piedmont plain of the Tianshan Mountains. An analysis of soil moisture potential and water content distribution shows that there exist different soil water movement mechanisms as well as changeable water transformation relationship between soil water and groundwater in the freezing-thawing process. If the water table is shallow, the soil water between the bottom boundary of freezing layer and the water table migrates upward. Water is accumulated around the boundary, resulting in the evaporation and loss of groundwater and the falling of the water table. Thus, the transport of groundwater to soil water is the dominating process in this case. If the water table is deep, however, the soil water movement is of upward-downward character. Although soil water migrates upward to the freezing layer, the water table remains rising due to infiltration recharge to groundwater. In this case, the transport of soil water to groundwater is the dominating process. In the thawing process, soil water movement in both cases gradually changes into the downward infiltration type, causing groundwater infiltration recharge. Snow accumulation and snow melt infiltration following the thawing of the freezing layer are vital for soil water resource and groundwater resource. In the arid region of northwestern China, these factors are very important in ecological and environmental protection.