Comparison and analysis of bare soil evaporation models combined with ASTER data in Heihe River Basin

Based on ASTER （Advanced Spaceborne Thermal Emission and Reflection Radiometer） remote sensing data, bare soil evaporation was estimated with the Penman-Monteith model, the Priestley-Taylor model, and the aerodynamics model. Evaporation estimated by each of the three models was compared with actual evaporation, and error sources of the three models were analyzed. The mean absolute relative error was 9% for the Penman-Monteith model, 14% for the Priestley-Taylor model, and 32% for the aerodynamics model; the Penman-Monteith model was the best of these three models for estimating bare soil evaporation. The error source of the Penman-Monteith model is the neglect of the advection estimation. The error source of the Priestley-Taylor model is the simplification of the component of aerodynamics as 0.72 times the net radiation. The error source of the aerodynamics model is the difference of vapor pressure and neglect of the radiometric component. The spatial distribution of bare soil evaporation is evident, and its main factors are soil water content and elevation.

Evaluating the soil evaporation loss rate in a gravel-sand mulching environment based on stable isotopes data

In order to cope with drought and water shortages,the working people in the arid areas of Northwest China have developed a drought-resistant planting method,namely,gravel-sand mulching,after long-term agricultural practices.To understand the effects of gravel-sand mulching on soil water evaporation,we selected Baifeng peach(Amygdalus persica L.)orchards in Northwest China as the experimental field in 2021.Based on continuously collected soil water stable isotopes data,we evaluated the soil evaporation loss rate in a gravel-sand mulching environment using the line-conditioned excess(lc-excess)coupled Rayleigh fractionation model and Craig-Gordon model.The results show that the average soil water content in the plots with gravel-sand mulching is 1.86%higher than that without gravel-sand mulching.The monthly variation of the soil water content is smaller in the plots with gravel-sand mulching than that without gravel-sand mulching.Moreover,the average lc-excess value in the plots without gravel-sand mulching is smaller.In addition,the soil evaporation loss rate in the plots with gravel-sand mulching is lower than that in the plots without gravel-sand mulching.The lc-excess value was negative for both the plots with and without gravel-sand mulching,and it has good correlation with relative humidity,average temperature,input water content,and soil water content.The effect of gravel-sand mulching on soil evaporation is most prominent in August.Compared with the evaporation data of similar environments in the literature,the lc-excess coupled Rayleigh fractionation model is better.Stable isotopes evidence shows that gravel-sand mulching can effectively reduce soil water evaporation,which provides a theoretical basis for agricultural water management and optimization of water-saving methods in arid areas.

STRUCTURAL DAMAGE MODEL OF UNSATURATED EXPANSIVE SOIL AND ITS APPLICATION IN MULTI-FIELD COUPLE ANALYSIS ON EXPANSIVE SOIL SLOPE

Focused on the sensitivity to climate change and the special mechanical characteristics of undisturbed expansive soil, an elasto-plastic damage constitutive model was proposed based on the mechanics of unsaturated soil and the mechanics of damage. Undisturbed expansive soil was considered as a compound of non-damaged part and damaged part. The behavior of the non-damaged part was described using non-linear constitutive model of unsaturated soil. The property of the damaged part was described using a damage evolution equation and two yield surfaces, i.e., loading yield （LY） and shear yield （SY）. Furthermore, a consolidation model for unsaturated undisturbed expansive soil was established and a FEM program named UESEPDC was designed. Numerical analysis on solid-liquid-gas tri-phases and multi-field couple problem was conducted for four stages and fields of stress, displacement, pore water pressure, pore air pressure, water content, suction, and the damage region as well as plastic region in an expansive soil slope were obtained.

Study of the phase-change coefficients of the cavitation model in cavitation flow fields generated from cone cavitator

The influence of phase-change coefficients variations in the Singhal cavitation model on the calculation results has been numerically studied. By comparing the numerical results and experimental data, the relationship between the coefficients and cavitation numbers is obtained. The calculation results of 2d axisymmetrical cylinder with 45-degree cone cavitator show that under different cavitation numbers, there are three typical kind of cavities, which are respectively main cavity, secondary cavity and rear cavity. The coefficients variations have a great influence respectively on the three type cavities in shape, collapse position, collapse strength, etc, and different cavitation numbers are corresponding to different phase-change coefficients. The cavitation flow field can be divided into three typical zones according to the cavitation number: weak-cavitation zone, secondary-cavitation zone and supercavitation zone. For 45-degree cone cavitator cylinder, the evaporation coefficients will firstly decrease and then increase with the decrease of cavitation numbers in secondary-cavitation zone, while the condensation coefficients keep relatively lower and almost unchanged. In weak-cavitation zone, there only exists the smaller main cavity attached to the model head or there is no obvious cavity. In supercavitation zone, the secondary cavity attached to the model will fall off and merge into the new rear cavity.

Effects of Spatial Information of Soil Physical Properties on Hydrological Modeling Based on a Distributed Hydrological Model

The spatial distribution of soil physical properties is essential for modeling and understanding hydrological processes. In this study, the different spatial information (the conventional soil types map-based spatial information (STMB) versus refined spatial information map (RSIM)) of soil physical properties, including field capacity, soil porosity and saturated hydraulic conductivity are used respectively as input data for Water Flow Model for Lake Catchment (WATLAC) to determine their effectiveness in simulating hydrological processes and to expound the effects on model performance in terms of estimating groundwater recharge, soil evaporation, runoff generation as well as partitioning of surface and subsurface water flow. The results show that: 1) the simulated stream flow hydrographs based on the STMB and RSIM soil data reproduce the observed hydrographs well. There is no significant increase in model accuracy as more precise soil physical properties information being used, but WATLAC model using the RSIM soil data could predict more runoff volume and reduce the relative runoff depth errors; 2) the groundwater recharges have a consistent trend for both cases, while the STMB soil data tend to produce higher groundwater recharges than the RSIM soil data. In addition, the spatial distribution of annual groundwater recharge is significantly affected by the spatial distribution of soil physical properties; 3) the soil evaporation simulated using the STMB and RSIM soil data are similar to each other, and the spatial distribution patterns are also insensitive to the spatial information of soil physical properties; and 4) although the different spatial information of soil physical properties does not cause apparent difference in overall stream flow, the partitioning of surface and subsurface water flow is distinct. The implications of this study are that the refined spatial information of soil physical properties does not necessarily contribute to a more accurate prediction of stream flow, and the selection of appropriate soil physical property data needs to consider the scale of watersheds and the level of accuracy required.

运行温度对钠热管内工质蒸发调节系数影响的实验研究

钠热管在相关小型化、无人化核反应堆平台上有着良好的应用前景,其工质蒸发调节系数的准确性对于钠热管分析具有重要的意义。而蒸发调节系数受温度的影响显著,为此,通过实验方法研究了不同温度对钠热管内钠蒸发调节系数的影响。通过改变加热功率、倾角、加钠量、丝网等参数,测量了稳态工况下的轴向外壁面温度及气相温度。采用不同蒸气温度取值方法,结合外壁面温度测量值,基于HertzKnudsen-Schrage方程获得了蒸发调节系数的实验值。分析表明,使用蒸发段局部气相温度作为蒸气温度获得的蒸发调节系数受管内工况及丝网参数影响较小,蒸发调节系数的对数值与对数饱和压力满足良好的线性关系;使用绝热段壁面温度或绝热段气相温度作为蒸气温度获得的蒸发调节系数,在550℃以下时受轴向导热热阻及液钠润湿不佳的影响,数值偏小但依然满足对数线性关系,而在高于550℃时液钠良好润湿性带来的轴向铺展可显著增大蒸发调节系数,此时丝网的作用较为明显。通过拟合实验数据,建立了不同温度下的蒸发调节系数的经验关系式。

基于蒸发皿蒸发量的设施番茄灌溉优化研究

[目的]针对日光温室番茄栽培的高效节水灌溉需求,进行基于蒸发皿水面蒸发量(E_(p))的日光温室番茄灌溉量优化研究。[方法]根据直径为20 cm的标准蒸发皿水面蒸发量(E_(p))设置3个灌溉量处理:1.0 E_(p)(CK)、0.8 E_(p)(T1)、0.6 E_(p)(T2),通过深入探讨番茄根系主要分布土壤层(0~40 cm)土壤含水量响应特征,结合对植株生长指标、果实产量和灌溉水利用效率的分析,进一步优化日光温室番茄栽培的灌溉量。[结果]灌溉量处理影响了土壤含水量的时空分布特征。CK、T1和T2处理0~40 cm土壤层平均土壤含水量为田间持水量的77.7%~103.4%、65.4%~98.9%、60.9%~91.1%,灌溉量越高土壤含水量越高;3个处理平均土壤含水量呈逐渐下降的趋势,且T1、T2处理下降幅度大于CK。随生育期推进,CK各土壤层土壤含水量的差异增加,T1和T2处理呈相反变化趋势。CK和T1处理0~10 cm土壤层土壤含水量波动幅度最大,T2处理为10~20 cm土壤层;整体上看,T1和T2处理处理各土壤层的土壤含水量波动幅度大于CK,但是转色期后T1处理30~40 cm和T2处理20~40 cm土壤层土壤含水变化不明显。番茄株高、茎粗、叶面积及地下、地上部鲜干重在不同处理之间的差异不显著(P>0.05)。与CK相比,T1和T2处理单果重和总产量分别降低了3.41%、4.07%和3.25%、3.97%,但番茄总产量的差异未达到显著水平(P>0.05)。3个处理灌溉水利用效率分别为30.1 kg·m^(-3)、35.1 kg·m^(-3)和43.9 kg·m^(-3),T1和T2处理相比CK分别提高了16.77%和46.15%。[结论]灌溉量为0.6 E_(p)的T2处理,0~40 cm土壤层平均土壤含水量维持在田间持水量60%以上,植株生长和果实总产量未受影响,灌溉水利用效率明显高于其它2个处理。因此,认为水面蒸发皿灌溉系数Kp0.6时为日光温室番茄提供了适宜灌溉量,有利于实现日光温室番茄节水高效栽培。

滴灌条件下温室黄瓜土壤蒸发的影响因素及模拟

明确土壤蒸发的变化过程和影响因素,建立简便且具有较高精度的计算模型,对提高水资源利用效率,减少无效水分消耗具有重要指导意义。以温室滴灌黄瓜为试验对象,对土壤蒸发进行了连续测量,引入Priestley-Taylor模型的土壤蒸发模块,将蒸发过程分为2个阶段,探讨了3个限制系数(Deardorff,1977:f_(sw)-1;Yao et al.,2013:f_(sw)-2;Ershadi et al.,2014:f_(sw)-3)对模型精度的影响。结果表明:全生育期温室滴灌黄瓜的土壤蒸发在0.13~9.15 g/d之间变化,平均值为3.15 g/d,总体表现为“增加-降低-增加”的变化趋势;土壤蒸发与表层含水率和LAI均呈e指数函数关系,与含水率呈正比,与LAI呈反比;土壤蒸发系数与含水率变化过程相似,全生育期在0.49~1.26之间变化;3个模型在第2阶段的模拟精度较高,且f_(sw)-1的精度优于f_(sw)-2和f_(sw)-3,MAE和RMSE分别为0.14和0.21 mm/d。因此,采用PT-f_(sw)-1模型模拟滴灌条件下的土壤蒸发具有较高精度,可为精确掌握温室滴灌黄瓜水分消耗提供依据。

不同类型重构土壤水分运移特征

为探究不同类型重构土壤对水分再分布过程和土壤持水量的影响,该研究以砒砂岩、砂黄土和粗砂土为试验材料进行室内土柱试验,设置5种不同类型重构土壤(砒-粗、砂-粗、砒-砂-粗、砂-砒-粗、混-粗),测定各处理在入渗过程、排水过程以及蒸发过程中土壤水分的动态变化;同时利用Hydrus-1D模型对不同类型重构土壤的入渗和蒸发过程进行模拟分析。结果表明,有砒砂岩层存在的重构土体对入渗过程有明显阻滞作用,且砒砂岩层越厚、位置越靠上阻滞效果越明显,土柱达到稳渗时稳渗率越低;蒸发过程中,砒-砂-粗处理累积蒸发量为52 mm,显著高于其他重构土壤(P<0.05),而砂-砒-粗处理土柱累积蒸发量最小(32.1 mm),蒸发结束时相对蒸发速率低至0.07;在蒸发过程中,上细下粗型层状重构土壤水分损失来自表层土壤和下层粗砂土。利用优化后的土壤水力参数和Hydrus-1D模型可以较好地模拟重构土壤水分运动过程。较低的均方根误差和高的决定系数证明模型能准确模拟各类型土柱的累积排水量、累积蒸发量和蒸发过程剖面含水量的动态变化。混-粗土柱的持水能力高于其他土柱,说明该重构类型可作为晋陕蒙地区土壤复垦的重构方案。

玉米芯颗粒对风沙土毛管水运移和蒸发特性的影响

为探索玉米芯在干旱地区的有效利用方式、提高其利用率,通过土柱模拟的方法,将1.5~6.0 mm玉米芯颗粒与风沙土混合开展吸水与蒸发试验。以未添加玉米芯的土柱为对照,设置10种添加玉米芯处理,对不同处理土柱的吸水量、湿润锋、蒸发量、蒸发强度等进行测定,分析玉米芯及其用量对风沙土吸水、保水效果的影响。结果表明,混合土壤毛管水上升高度比对照低0.0%~76.3%,毛管水平均上升速率比对照低7.3%~78.7%,蒸发强度比对照低10.7%~64.2%。玉米芯添加量≤40%时,吸水量比对照高8.6%~16.2%;玉米芯添加量>40%时,吸水量比对照低1.1%~46.0%。毛管水上升高度与时间之间呈幂函数关系,水分补给量与时间之间呈幂函数关系,水分补给量与毛管水上升高度之间呈线性相关。吸水条件下的Green-Ampt模型调整后可用于模拟混合土壤的毛管水上升过程。Rose蒸发模型能很好地表达混合土壤累计蒸发量随时间的变化特征。研究结果为沙化土地治理、秸秆还田改良耕地等研究与实践提供理论依据。

Soil-atmosphere interaction in earth structures

The soil-atmosphere interaction was investigated through laboratory testing,field monitoring and numerical monitoring.In the laboratory,the soil water evaporation mechanisms were studied using an environmental chamber equipped with a large number of sensors for controlling both the air parameters and soil parameters.Both sand and clay were considered.In case of sand,a dry layer could be formed during evaporation in the near surface zone where the suction corresponded to the residual volumetric water content.The evaporative surface was situated at a depth where the soil temperature was the lowest.In case of clay,soil cracking occurred,changing the evaporative surface from one-dimensional to three-dimensional nature.The suctionbased evaporation model was adapted to take these phenomena into account by adopting a function of dry layer evolution in the case of sand and by adopting a surface crack ratio and a retative humidity ratio in the case of clay.In the field,the volumetric water content,and the suction as well as the runoff were monitored for an embankment constructed with lime/cement treated soils.It appeared that using precipitation data only did not allow a correct description of the variations of volumetric water content and suction inside the soils,the consideration of water evaporation being essential.It was possible to use a correlation between precipiration and runoff.The hydraulic conductivity was found to be a key parameter controlling the variations of volumetric water content and suction.For the numerical modelling,a fully coupled thermohydraulic model was developed,allowing analyzing the changes in temperature,volumetric water content and suction of soil,with the upper boundary conditions at the interface between soil and atmosphere determined using meteorological data.Comparison between simulations and measurements showed the performance of such numerical approach.

Estimation of evapotranspiration from artificial forest in mountainous areas of western Loess Plateau based on HYDRUS-1D model

Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and water resource management.Artificial forests are an important means of vegetation restoration in the western Loess Plateau,and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests.This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis(L.)Franco forest in western mountains of Loess Plateau,China from 20 April to 31 October,2023.Moreover,the influence factors were identified by combining the correlation coefficient method and the principal component analysis(PCA)method.The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October,2023.The soil water accumulation was 49.64 mm;the potential evapotranspiration(ETp)was 809.67 mm,which was divided into potential evaporation(Ep;95.07 mm)and potential transpiration(Tp;714.60 mm);and the actual evapotranspiration(ETa)was 580.27 mm,which was divided into actual evaporation(Ea;68.27 mm)and actual transpiration(Ta;512.00 mm).From April to October 2023,the ETp,Ep,Tp,ETa,Ea,and Ta first increased and then decreased on both monthly and daily scales,exhibiting a single-peak type trend.The average ratio of Ta/ETa was 0.88,signifying that evapotranspiration mainly stemmed from transpiration in this area.The ratio of ETa/ETp was 0.72,indicating that this artificial forest suffered from obvious drought stress.The ETp was significantly positively correlated with ETa,and the R2 values on the monthly and daily scales were 0.9696 and 0.9635(P<0.05),respectively.Furthermore,ETa was significantly positively correlated with temperature,solar radiation,and wind speed,and negatively correlated with relative humidity and precipitation(P<0.05);and temperature exhibited the highest correlation with ETa.Thus,ETp and temperature were the decisive contributors to ETa in this area.The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests,and deepen understanding of effects of each influence factors on ETa in arid areas.

基于双作物系数法估算晋南地区冬小麦-夏玉米轮作系统蒸散量

冬小麦-夏玉米轮作系统是晋南地区常用的种植模式,为评估双作物系数法在冬小麦-夏玉米轮作系统应用的可靠性,掌握轮作系统耗水规律,通过双作物系数法模拟2016-2019年间冬小麦-夏玉米轮作系统蒸散量,以水量平衡计算结果为标准对其模拟结果进行评价,并区分植株蒸腾(T)和土壤蒸发(E)。该结果表明:在冬小麦-夏玉米轮作系统中,冬小麦初期、发育期、中期和后期的平均基础作物系数(Kcb)为0.2、0.59、0.98和0.15,夏玉米的为0.14、0.69、1.24和0.56;冬小麦的平均土壤蒸发系数(Ke)为1.24、0.63、0.07、0.42,夏玉米的为0.78、0.45、0.06、0.46。冬小麦全生育期内ETc为264.18~526.22 mm,夏玉米的为261.76~519.67 mm;发育期为耗水高峰期,冬小麦、夏玉米发育期蒸散量占各自生育期总蒸散量的比例分别为31.2%~51.3%和34.3%~58.2%;随着灌水次数的减少,冬小麦、夏玉米总蒸散量及植株蒸腾量均逐渐降低,土壤蒸发量也在灌水最少时达到最低,全生育期E/ETc,冬小麦为27.3%~46.4%,夏玉米为29.3%~44.2%。在冬小麦和夏玉米生长初期,80%以上的土壤水分以蒸发形式消耗,在中期时土壤蒸发占比最低,冬小麦为6.1%~13.4%、夏玉米为4%~7.6%。冬小麦、夏玉米各自蒸散模拟值(ETc-FAO)与实测值(ETc)呈现出较好相关性,R2为0.8~0.86,RMSE为0.5~0.6 mm/d,MAE为0.4~0.49mm/d,可见双作物系数法模拟晋南地区冬小麦-夏玉米轮作系统ETc具有较高精度,可为精确掌握冬小麦-夏玉米轮作系统耗水规律,进而制定合理的灌溉计划提供理论依据。

利用Penman-Monteith-Leuning模型和Sentinel-2数据的灌区蒸散发反演

针对目前基于Penman-Monteith-Leuning模型(PML)的蒸散发模拟研究中,存在因多种地表参数的时空尺度差异导致蒸散发反演误差这一问题,提出了一种耦合土壤含水量改进模型土壤蒸发系数f的参数化方案。通过Sentinel-2影像反演土壤含水量、LAI等模型关键参数,并基于土壤含水量计算f,在河套灌区建设二分干灌域开展蒸散发反演,结合地面观测数据进行验证。结果表明:模型反演结果与涡动相关站实测数据有较好的一致性;在植被覆盖度较低时,改进的f参数化方案能更好地反映土壤蒸发的实际情况;该反演结果较为准确地反映了不同下垫面的蒸散发空间异质性。文章对蒸散发反演方法和数据的尝试,可为高分辨率蒸散发反演方法提供参考,并为干旱区和半干旱区的农业用水管理提供技术支持。

季节性冻融期SWAP和SHAW模型土壤水热运移模拟效果评价

基于不同模型研究季节性冻融期土壤水热运移规律,对干旱半干旱地区水资源高效利用的定量化评价具有重要意义。分别运用SWAP和SHAW模型对季节性冻融期土壤水分、温度和蒸发量进行了模拟,并对模拟效果加以评价。模拟结果表明:对于整个冻融期而言,利用SHAW模型模拟的土壤含水量的NRMSE基本保持在30%以内,RMSE均在0.09 cm^(3)/cm^(3)以下,利用SWAP模型模拟的土壤含水量的NRMSE基本保持在35%以内,RMSE均在0.13 cm^(3)/cm^(3)以下;利用SHAW模型模拟20 cm以下土层温度的NRMSE均保持在30%以内,RMSE均在0.94℃以下,利用SWAP模型模拟的土壤温度基本可以反映实测值的变化趋势;在模拟土壤累积蒸发量方面,相比SWAP模型,SHAW模型的模拟值更接近实测值。总体而言,在干旱半干旱地区对于季节性冻融期,SHAW模型对土壤水热运移的模拟效果均较为理想,SWAP模型对土壤水分运移模拟较好,但对土壤温度模拟相对较差。对于土壤累积蒸发量的模拟效果,两个模型均不十分理想,有待进一步改进。

黑河下游胡杨林生态系统土壤蒸发模拟改进

水分是限制干旱、半干旱地区植被生态系统恢复的重要因素之一,合理量化长时间尺度下生态系统中的土壤蒸发量及其变化趋势,对于提高生态系统水资源利用效率具有重要意义。基于黑河下游额济纳绿洲七道桥胡杨林保护区实测数据,分析了胡杨林生态系统土壤蒸发和蒸散发的变化趋势及其与环境因子的相关性,通过Shuttleworth-Wallace模型和改进的双源模型中土壤蒸发的计算公式对其进行模拟,对比分析了二者的模拟精度及参数敏感性,结果表明:(1)土壤蒸发和蒸散发各月的日变化及整个试验期内的变化均呈先升高后降低的单峰变化趋势;(2)胡杨林生态系统土壤蒸发在蒸散发中所占比例的变化范围为30.2%~72.2%;(3)净辐射对土壤蒸发的影响最显著;(4)改进的双源模型中,土壤蒸发的计算公式可以不考虑复杂阻力参数的计算过程,且与传统的双源SW模型相比具有更高的模拟精度。研究提出了适用于干旱区森林植被生态系统中土壤蒸发模拟的双源优化模型,为土壤蒸发模拟提供了新的思路与方法。

基于Hydrus-1D模型的淮北平原冬小麦地潜水蒸发规律

选取淮北平原五道沟水文水资源实验站作为研究区,评价Hydrus-1D模型在淮北平原冬小麦地潜水蒸发过程模拟的适用性,并探讨不同降水条件下冬小麦各生育期潜水蒸发规律。结果表明,基于Hydrus-1D模型模拟的潜水蒸发过程与基于水量平衡和Bouchet互补关系理论的潜水蒸发变化过程基本一致,相关系数为0.82、绝对误差为0.04 mm/d、相对误差为12.4%;冬小麦生育期潜水蒸发量受降水条件影响,当降水量偏多时,潜水蒸发总量较大;从冬小麦各生育期的潜水蒸发量来看,灌浆期-成熟期>抽穗期-灌浆期>拔节期-抽穗期>返青期-拔节期。研究结果可为制定淮北平原合理灌溉制度提供理论依据。

冻融作用下土壤不均匀系数对潜水与土壤水转化的影响

为了揭示冻融过程中土壤不均匀系数对潜水与土壤水转化的影响,在室内进行了-10、-20和-25℃依次降温恒温冻结62 d和自然消融10 d的冻融试验,研究了不均匀系数(Cu)为2.00(土柱A)、3.70(土柱B)、6.36(土柱C)、16.18(土柱D)和20.67(土柱E)的5个土柱在0.5 m地下水位埋深下的土壤温度、潜水蒸发量及潜水回补量变化特征。结果表明:在冻融过程中,土壤颗粒的不均匀系数越大,土壤剖面温度变化幅度越大。随着土壤深度的增加,土柱A和土柱E冻结结束时的温度差减小,不均匀系数对土壤剖面温度的影响减小。冻结0~3 d时,土柱A、B、C、D和E的潜水蒸发速率分别为0.11、0.15、0.23、0.27和0.39 mm/d,潜水蒸发速率相对较小,但不均匀系数越大,潜水蒸发速率越大;冻结结束(第62 d)时土柱A、B、C、D和E的累积潜水蒸发量分别为15.17、21.46、28.23、34.96和38.65 mm,累积潜水蒸发量与土壤不均匀系数较好的符合对数函数的关系,潜水与土壤水的转化量随土壤颗粒不均匀系数增大而增加。

Models for calculating phreatic water evaporation on bare and Tamarix-vegetated lands

地下水是在干旱区域的自然植被的水消费的主要来源。由井的蒸发学习自然植被的生态的水需求是一条有效途径。为了学习生态的水， Tarim 河盆要求，基于以 Aksu 水平衡的赤裸的陆地上的井的蒸发的观察数据从 1989～1996 的试验性的车站由分析井的蒸发的关系，井的表面的深度和水的蒸发，拿限制井的蒸发的率作为控制条件，并且基于在水的井的蒸发和蒸发之间的关系是非线性的客观法律，我们建立当 pheratic 水平衰落就被土壤水分蒸发蒸腾损失总量从 2003 ～ 2004 在生长 Tamarix 的土地上引起时，根据井的表面和土壤潮湿的深度的数据，我们计算井的蒸发的数量并且在生长 Tamarix 的土地上为精明的井的蒸发建立模型。赤裸的土地和生长 Tamarix 的土地上的井的蒸发能被一个 Tamarix 植被变换系数互相转变。测试结果证明模型的计算精确性高，模型对 Tarim 河盆合适。

基于蒸发法和联合测定仪测定土壤水分特征曲线和非饱和渗透系数的试验研究

为确定以蒸发法为基础设计的土壤水分特征曲线和非饱和渗透系数联合测定仪的可靠性和适用范围,选取粉黏壤土、壤土和壤砂土3种土样进行试验研究。在自然蒸发作用下,利用联合测定仪获得蒸发通量、含水量和土柱表面下方5,10 cm处的基质吸力,以线性假设理论为基础处理实测数据,利用HYDRUS-1D软件进行模拟和反演,输入实测基质吸力和通量数据确定土壤水力参数,利用RETC软件对已处理数据进行VG-Mualem模型拟合。结果表明,含水率符合线性假设理论,基质吸力线性变化不是很理想,但除砂土之外的土样可以通过降低蒸发速率和缩短2次测量时间间隔来解决这个问题;试验数据的拟合效果好,与模拟结果的误差较小,试验前期所测非饱和渗透系数与模拟值误差较大,主要跟含水率接近饱和时水力梯度的精度不能得到保证有关,可以忽略这些数据来改进。使用蒸发法和联合测定仪测定土壤水分特征曲线和非饱和渗透系数具有比较好的可靠性。