华北平原中部典型区包气带水分时空动态变化特征

目的]研究包气带水分时空动态变化特征,为"四水转化"系统动态循环研究提供依据。方法]利用土壤水分运动学中势能的观点,研究包气带水分、包气带水势随时间和深度的变化特征。结果]季节不同,土壤水势整体分布差异明显。6—8月土壤水势最高,局部地段甚至达到饱和,12月至翌年3月土壤水势最低。地面0—50cm深度土壤含水量受季节影响非常大,土壤水势激烈变化;50cm深度以下土壤含水量基本不受季节交替影响,50—140cm土壤水势相对稳定;140cm以下只受重力势作用。结论]降雨、灌溉、蒸发、地下水埋深等因素均能引起土壤剖面土壤水势分布发生变化,从而实现入渗型、蒸发型、蒸发—入渗型、下渗—上渗型、下渗—上渗—入渗型等土壤水分运动状态的相互转化。

Temporal and Spatial Variation Characteristics of Soil Moisture Variation in Vadose Zone at Typical Area of Central North China Plain

Objective] To analyze the spatial and temporal characteristics of the soil moisture variation in vadose zone in order to provide basis for the study on the "four waters transformation" dynamic cycle.Methods] Using the concept of the potential energy of soil water dynamics, the characteristics of the moisture in vadose zone and changes in water potential with time and depth was studied.Results] The significant difference was observed in soil water potential distribution in each season. Soil water potential reached the highest in June and August, even got saturation in some blocks. On the contrary, it dropped to a minimum in period from December to next March. Soil moisture of 50 cm depth was affected greatly by seasons and water potential changed dramatically. Yet soil moisture below 50 cm depth was substantially independent of the season changes. And between 50-140 cm depth water potential was relatively stable; Beneath 140 cm, it was only influenced by gravity potential.Conclusion] The factors such as rainfall, irrigation, evaporation, groundwater depth and others could cause the changes in the profile distribution of soil water potential, thus causing changes among a variety of soil water movement states.