裸土蒸发是干旱半干旱地区能量平衡和水文循环的重要组成部分，土壤蒸发强度的大小与净辐射、空气温度、相对湿度、风速、土壤质地以及包气带岩性等众多因素密切相关，使得土壤蒸发的计算十分复杂。研究表明，旱区地下水蒸发是重要的排泄项，土壤—地下水蒸发计算准确与否，直接影响着旱区地下水资源量的评价精度。因此，开展土壤—地下水蒸发解析对评价水资源量具有十分重要的理论意义和应用价值。 本文以毛乌素沙地风积沙为研究对象，以土壤水动力学、土壤热力学、土壤物理学、水文地质学等理论为指导，采用室内试验、原位试验以及数值模拟相结合的方法，开展了蒸发条件下包气带水分运移研究。首先，开展了室内蒸发试验，提出了考虑土壤质地的蒸发公式，并与常用经验公式进行对比，探讨了该公式在计算毛乌素沙地风积沙蒸发中的适用性；其次，开展了土壤—地下水蒸发原位试验，分析了蒸发速率与净辐射，空气温度，相对湿度以及风速的相关性；再次，以原位试验为基础建立了土壤—地下水运移数值模型，预测了不同潜水埋深条件下潜水蒸发比值以及土壤水对蒸发的贡献率。主要结论如下： （1）室内试验表明，随着潜水埋深的增加，蒸发强度逐渐减小，当潜水埋深大于71cm后，潜水蒸发强度接近于0，因此毛乌素沙地潜水极限蒸发深度为71cm。 （2）建立了基于土壤质地的潜水稳定蒸发公式，即，与常用的经验公式相比，该公式在计算毛乌素沙地潜水稳定蒸发时具有更好的拟合效果。 （3）原位试验监测表明，潜水埋深较浅时，裸土的潜水蒸发强度与净辐射、风速和空气温度呈正相关，而与相对湿度呈负相关。 （4）数值模拟表明：①当潜水埋深小于等于30cm时土壤水贡献率与潜水埋深呈指数型函数关系，即的分布规律，当潜水埋深大于30cm时土壤水贡献率与潜水埋深呈幂函数关系，即的分布规律。②潜水埋深与潜在蒸发比值呈指数型函数关系，即的分布规律。 上述成果表明，随着潜水埋深的增加，土壤水及地下水对蒸发的贡献率呈非线性变化规律，这对提高旱区水资源的评价精度具有一定的指导意义，同时也可为旱区水资源评价提供借鉴。

Bare soil evaporation is an important compont of energy balance and hydrological cycle in arid and semi-arid regions. Soil evaporation is closely related to net radiation, air temperature, relative humidity, wind speed, soil texture and the lithology of aeration zone, so the calculation of soil evaporation is very complicated. Studies have shown that groundwater evaporation is an important discharge in arid areas, and the accuracy of soil-groundwater evaporation calculation directly affects the evaluation accuracy of the quantity of groundwater. Therefore, it is of great theoretical significance and practical value to carry out the analysis of soil-groundwater evaporation for the evaluation of water resources. In this paper, the aeolian sand in Mu Us Desert is taken as the research object, and soil hydrodynamics, soil thermodynamics, soil physics, hydrogeology and other theories are taken as the guidance. A study on water transport in vadose zone under evaporation conditions was carried out by means of laboratory test, in-situ test and numerical simulation. Firstly, indoor evaporation tests were carried out and the evaporation formula considering the soil texture is proposed, and compared with the commonly used empirical formula, and the applicability of the formula in Mu Us Desert is discussed. Secondly, the in-situ test of soil-groundwater evaporation is carried out, and the correlation between evaporation rate and net radiation, air temperature, relative humidity and wind speed is analyzed. Finally, a numerical model of soil-groundwater migration was established based on in-situ test, and the phreatic evaporation ratio and contribution rate of soil water under the condition of the different phreatic water depth were predicted. In conclusion, the following works have been done in the study. The laboratory test shows that the evaporation intensity gradually decreases with the increase of the buried depth of diving. When the buried depth is 71cm, the evaporation intensity of diving is close to 0, so the maximum evaporation depth of diving in Mu Us Desert is 71cm. The formula of phreatic steady evaporation based on soil texture is proposed, , which has better fitting effect than the empirical formula in calculating steady phreatic evaporation in Mu Us Desert. The in-situ test shows that the shallow water evaporation intensity of bare soil is positively correlated with net radiation, relative humidity and air temperature, but negatively correlated with relative humidity. The numerical simulation results show that: ①When the depth of phreatic water is less than or equal to 30 cm, the contribution rate of soil water is exponential function with the depth of phreatic water and follows the distribution law of . When the depth of phreatic water is greater than 30 cm, the contribution rate of soil water is power function with the depth of phreatic water and follows the distribution law of . ②The diving depth and the potential evaporation ratio are exponentially functional, obeying the distribution law of . The above results show that the contribution rate of soil water and groundwater to evaporation varies nonlinearly with the increase of phreatic depth, which has a certain guiding significance for improving the evaluation accuracy of water resources in arid areas.