浅层包气带土壤水昼夜分布变化规律模拟研究

西北干旱半干旱地区,浅层包气带含水率与地温等地下水文要素的分布特征对保护旱区表生生态环境起到至关重要的作用。以鄂尔多斯风沙滩地区原位土柱试验为基础,采用HYDRUS-1 D对一维入渗过程的水蒸汽变化、含水率和温度分布进行数值模拟并通过实测值进行验证。结果表明:温度梯度对浅层包气带土壤含水率昼夜变化及水蒸汽通量分布起到主控作用;日尺度剖面水蒸汽运动过程可分为3个阶段:阶段1(1:00-7:00),阶段2(8:00-16:00)及阶段3(17:00-23:00);当温度梯度方向向上,水蒸汽通量向上运动时,含水率变小,反之,含水率变大。利用HYDRUS模型分析水蒸汽的运动规律,揭示了土壤温度对土壤水分布的影响机制,为旱区蒸发过程及生态环境保护提供科学依据。

Simulation study on diurnal distribution variation of soil water in shallow vadose zone

In the arid and semi-arid regions of Northwest China, the distribution characteristics of subsurface hydrological elements such as soil water content and temperature in shallow vadose zone play vital roles in protecting the epigenetic ecological environment. Based on the in-situ soil column experiment in wind-blown sand area of Ordos Basin, the water vapor movement, soil water content and temperature distributions of one-dimensional infiltration process were numerically simulated using HYDRUS-1 D model, and verified by the measured values. The results showed that the temperature gradient plays a dominate role in the diurnal distributions of soil water content and water vapor flux in shallow vadose zone. Water vapor movement process can be divided into three stages in daily-scale: stage 1 (1:00-7:00), stage 2 (8:00-16:00), and stage 3 (17:00-23:00). Water vapor flux moved upwards and the water content decreased when the direction of temperature gradient was upward; conversely, the water content increased. Using the HYDRUS model to analyze the water vapor movement, and reveal the mechanism of soil temperature on soil water distribution can provide a scientific basis for evaporation process and ecological environment protection in arid areas.