间歇降雨中土壤含水量分布及其对入渗的影响

通过室内土柱实验,研究了间歇性降雨事件中土壤剖面水分分布特征及其对入渗的影响.实验表明,积水发生时间与雨强和表层5 cm初始土壤含水量密切相关;前期累积入渗量越大.则土壤表面越容易发生积水;间歇入渗过程中,入渗还受间歇时间的影响,相邻入渗事件积水发生时间有提前的趋势.初始事件入渗速度较后续入渗大一个数量级;湿润锋运行速度存在明显的波动,在经历间歇期再分布后,湿润锋运动存在滞后效应,且波动作用较初始入渗更加显著.通过分析,认为土壤水入渗以运动波和扩散波的形式运动,两者交替起主要作用,土壤水分有随含水量升高以运动波传递,随含水量衰减以扩散波形式运动的趋势.

Distribution Characteristics of Initial Soil Water Content in Profile During Hiatus Rainfall-infiltration Events and Its Effects on Infiltration

The distribution characteristics of initial soil water content in profile during hiatus rainfall-infiltration events and its effects on infiltration were discussed in this study based on in door rainfall-infiltration experiments on soil column apparatus. It shows that the ponding time in rainfall-infiltration events are closely related with rainfall rate and initial soil moisture in above 5cm soil layer. With more antecedent cumulative infiltration, the soil column is more liable to pond. In hiatus rainfall-infiltration events, infiltration is also determined by the length of hiatus period and the ponding time tends to be advanced in successive events. The mean velocity of wetting front of the first events in the hiatus rainfall is always an order higher than that of successive events. In hiatus events, the velocity of wetting front is obvious fluctuant. After redistribution in the hiatus period, there tends to be a hysteresis with the wetting front and the fluctuation is more prominent. We argued that soil flow is moved by a manner of kinematic wave and diffusion wave and these two waves will be dominant alternatively. The soil flow tends to be in kinematic wave with higher soil moisture and tends to be in diffusion wave with relative lower soil moisture.