负水头环境土壤水分湿润锋运移三维模拟

Three-dimensional Model and Verification of Soil Wetting Front Migration in Negative Head Environment

【目的】更加有效地控制土壤含水率,指导节水灌溉。【方法】采用负水头土壤水分湿润锋运移试验和Hydrus-3D三维土壤水分运移数值模型,研究了山西榆次砂土、壤土在负水头高度(0、-0.5、-1.0m)时的土壤水分湿润锋运移规律和模型的有效性。【结果】水分累积入渗量随着时间的增加逐渐增大,与时间呈良好的幂函数关系;湿润锋随着时间的增加逐渐向水平、垂直方向扩大,曲线呈1/4椭囿状,最大湿润距离与时间的平方根呈良好的线性关系;湿润锋入渗速度随着负水头高度的增加逐渐减小,与时间呈良好的幂函数关系。实测湿润锋包络面积与模型计算值的偏差,砂土为0.51%~7.21%,壤土为0.22%~16.03%。【结论】所建三维模型可以用于描述负水头环境下土壤水分湿润锋的运移特征,并用于预测各种条件改变下的湿润锋运移和含水率分布。

【Objective】This study aimed to control soil water content more effectively and guide water-saving irrigation.【Method】The sand and loam in Yuci area of Shanxi Province were selected to establish soil wetting front migration experiments under three kinds of negative head height(0 m,-0.5 m,-1.0 m). The negative head soil moisture wetting front migration test and Hydrus-3 D soil moisture migration numerical model were used to research the law of soil moisture wetting front migration and the validity of the model.【Result】The cumulative infiltration increases with the increase of time, and also can be expressed by power function. With the increase of time, the wetting front gradually expands to horizontal and vertical directions, and not only the curve presents a 1/4 elliptic shape, but also the maximum wetting distance with the square root of time can be expressed by linear relation. The infiltration velocity of wetting front decreases with the increase of negative head height and can be expressed by power function too. The measured wetting front envelope area at negative head of-0.5 m and-1.0 m was used as model validation data. The deviation of wetting front envelope area between numerical calculation and measured, is 0.51%~7.21% for sandy soiland 0.22%~16.03% for loam.【Conclusion】The three-dimensional model can be used to describe the migration characteristics of soil wetting front in negative head environment, and to predict the movement and distribution of moisture content under different conditions.