干旱区高盐度潜水蒸发条件下土壤积盐规律分析

为分析干旱区高盐度潜水蒸发条件下土壤中盐分积累规律,利用室外土柱模拟试验开展了不同TDS(Total Dissolved Solids)(30和100 g/L)、不同包气带质地(细砂和粉质黏土)和不同潜水埋深(0.5、1.0和3.0 m)的高盐度潜水蒸发条件下分层土壤盐分的监测工作。通过对各个土柱不同深度7次取样得到的土壤平均含盐量数据分析表明:高盐度潜水蒸发条件下,潜水埋深越浅,土壤剖面上相同深度范围内的含盐量就越大;在其他条件一定时,包气带质地为粉质黏土的土壤剖面含盐量大于包气带质地为细砂的土壤剖面含盐量;由于黏性土的膜效应和土壤中积盐对土壤孔隙的填充作用,导致粉质黏土土柱上层的土壤含盐量表现为潜水TDS为30 g/L的大于潜水TDS为100 g/L的,在土柱下层的土壤含盐量表现为潜水TDS为30 g/L的小于潜水TDS为100 g/L的;由于TDS升高对毛细水的重力和土体结构的改变,随着潜水TDS的升高,粉质黏土土壤剖面上出现局部积盐深度下移的趋势。     

降水补给地下水过程中包气带变化对入渗的影响

采用野外试验和室内试验方法,通过对不同降水量的入渗过程中岩土含水率和水势变化规律分析,发现入渗水流在包气带内下渗过程的岩土吸水、过水(即水分通量不变、且不等于零)和脱水的不同阶段,当岩土水势的梯度分别大于、等于和小于1cmH2O/cm(厘米水柱/厘米)时,岩土含水率分别表现为增加、稳定和减少。对包气带不同埋深的岩土含水率和水势变化特征分析表明,随着地下水位不断下降,包气带增厚对降水入渗补给地下水的影响程度和方式都发生改变。当包气带厚度小于潜水蒸发极限深度时,包气带的增厚使得岩土水分亏缺累积量增大,导致入渗速率和地下水获取的总入渗补给量减小;当包气带厚度大于潜水蒸发极限深度时,随着包气带厚度增大,入渗速率趋于稳定,无限时间内地下水获取的总入渗补给量不因包气带增厚而变化,但是有限时间内地下水获取的入渗补给量趋小。这是因为入渗途径的延长导致入渗所需时间增加,以至在有限时间内包气带内过剩的入渗水分尚未充分排出补给地下水。     

作物根区底部土壤水分向上运移通量的计算方法

本文用河北雄县试验站的实测资料验证了一维土壤水动力学模型—WAVE模型(Water and Agrochemicals in the Soil and Vadose Environment)，率定了土壤水力学特性参数和作物根系吸水函数。在此基础上，应用该模型模拟不同地下水埋深和不同作物腾发量条件下根区底部向上水分通量的变化，从而得到地下水对根层的补给量与根层土壤储水量的关系。把这一关系用于制定和评价灌溉制度的水量平衡模型当中，提高了模型的适用范围和模拟精度。     

Vadose-zone moisture dynamics under radiation boundary conditions during a drying process

In order to better understand the soil moisture dynamics during a drying process, a soil column experiment is conducted in the laboratory, followed by the numerical modeling with consideration of the coupled liquid water, water vapor and heat transport in the vadose zone. Results show that there are three distinct subzones above the water table according to the temporally dynamic variation of the water content profiles. Zone 1 sees a decrease in the water contents in the upper profiles （0 m-0.05 m） due to a negative net water flux in this zone where the upward isothermal water vapor flux becomes the main flow mechanism in the soils. Irl contrast, the water content within Zone 2 in the depth ranging from 0.05 m to 0.37 m sees an apparent increase over the, resulting from the positive net thermal water-vapor and isothermal liquid-water fluxes into this layer. Zone 3 （0.37 m-0.65 m） also sees an apparent decrease in the water content since the isothermal liquid water flux carries the liquid water either upward out of this region for vaporization or downward to the water table as a recharge to the groundwater.     

兴平地区渭河南岸潜水防污性评价

在干旱半干旱地区,地下水是主要供水水源之一.目前水体污染、水资源短缺、水生态失衡,导致干旱半干旱地区经济发展与水安全保障的矛盾日益尖锐.以兴平地区渭河南岸为例,利用DRASTIC方法,选取潜水埋深、净补给量、含水层介质类别、土壤介质类别、地形坡度、包气带介质类别以及渗透系数为防污性7项评价因子,构建了潜水防污性评价指标体系,对该地区的潜水防污性进行了分区评价,将兴平地区渭河南岸的潜水防污性分为防污性差和防污性较差两个等级,并绘制了潜水防污性评价分区图,为该地区工农业生产的发展和城市规划提供了科学的依据.     

基于元数据分析的西北干旱区生态地下水位埋深及其影响因素

综合现有文献研究成果, 基于元数据分析方法研究不同植被的适宜、极限生态地下水位埋深。选择乔木、灌木 和草本等 3 种植被类型中的 13 种植物, 分析适宜、极限生态地下水位埋深的统计分布、生物多样性和丰富度指数, 推求生态地下水位埋深与植物根系和土壤质地的关系, 得出: 西北地区适宜和极限生态地下水位埋深均值分别为 2. 9、5. 5 m, 控制范围分别为 2. 3~ 3. 9、4. 0~ 7. 2 m; 适宜、极限生态地下水位埋深与植物根系具有显著的相关关系, 适宜生态地下水位埋深还取决于植物根系伸展速率与地下水位埋深下降速率的相对关系; 土壤质地控制毛细管上升高度及地下水位埋深以上水分供给能力, 是确定生态地下水位埋深的重要因子。     

北京市南水北调工程受水区典型非正规垃圾场地下水安全性评价

对北京市南水北调工程受水区26处非正规垃圾场地区地下水安全性的影响因素进行分析,采用DRASTIC方法和模糊综合评判法相结合的地下水安全性评价方法,选取地下水埋深、含水层介质类型、土壤类型、包气带介质类型、氯离子、总硬度和硝酸盐等7个影响因子作为评价指标,并用层次分析法确定各指标权重,最终计算出北京市南水北调受水区26处非正规垃圾场地区地下水安全性评价综合评分值,并划分了各垃圾场地区的地下水安全性等级:5个一级区安全性较高,15个二级区次之,6个三级区地下水安全性最低。     

第二松花江流域平原区浅层地下水脆弱性时变特征分析

以第二松花江流域平原区为研究区,选择了地下水埋深、净补给量、含水层介质、土壤介质、地形坡度、包气带影响、渗透系数7个指标,运用DRASTIC评价方法对浅层地下水脆弱性进行了评价,进一步分析了地下水脆弱性评价结果的影响因素。结果表明:(1)地下水脆弱性分区在整体上具有空间分带特征性,并与地貌分区具有良好的一致性,其中河谷平原区由于地下水埋藏较浅,地下水脆弱性较高,污染风险大;(2)受地下水位变动以及净补给量的影响,具体地段的地下水脆弱性等级也具有较为明显的年际与年内变化特征,但整体区域上的地下水脆弱性的相对级别仍受地貌格局的控制。在开展区域地下水脆弱性评价时,应注意选择具有代表性的时段数据进行评价。     

Modeling Transient Evaporation from Descending Shallow Groundwater Table Based on Brooks–Corey Retention Function

In arid and semi-arid regions a large amount of rainfall and irrigation water that enters into the soil is lost through soil surface via evaporation. In such regions, there are some areas with shallow groundwater table, evaporating huge amounts of water and accumulating salts at the soil surface. Thus, the evaporation phenomenon not only is responsible for water loss but also is a major reason for soil salinization. The objective of this study was to develop and verify an analytical model for one dimensional transient unsaturated upward flow from water table to soil surface. Consequently, an analytical solution was developed based on the Richards equation with initial and boundary conditions governing evaporation phenomenon. The parametric Brooks and Corey retention function was used to describe water status in the vadose zone. Based on the proposed model, the saccumulative evaporation is estimated as function of water table drawdown and soil retention parameters. To collect the data required for model verification, nine large lysimeters were constructed and packed with sandy loam, silty clay loam, and silty clay soil textures. The results indicated reasonable agreements between the experimental data and those predicted with the proposed model. Although the overall predicted results were well resemble the real conditions, there were some underestimations for a certain period. This can be attributed to evaporation from side gap of columns, upward flow due to vapor phase movement of moisture, and the collapse of macropores resulting from soil packing.     

新型蒸渗仪及其在农田水文过程研究中的应用

一台用于测定农田蒸腾蒸发和地下水—土壤水转化的新型称重式蒸渗仪在中国科学院禹城试验站建造完成，并连续数年成功运行。新型蒸渗仪主要有以下特点：(1)蒸渗仪精度0.016mm，可同时准确测量蒸腾蒸发量和地下水对土壤水的补给量与入渗量；(2)蒸渗仪面积3.14m2，深度5m，充分允许农作物根系发育与吸水、土壤水和地下水水分转化、地下水位变化等过程的进行，可以较好的代表大田的情形；(3)蒸渗仪的供排水系统能够在蒸渗仪内模拟实际地下水位变化；(4)土柱重30～34Mg，包含非饱和与饱和土壤，土壤质地以粉沙和轻壤为主。自1998年10月至1999年6月冬小麦生长期蒸渗仪运行结果表明：在冬小麦生长期，当地下水在1.6～2.4m变动时地下水对土壤水的补给量约占总蒸腾蒸发量的16.6%.过多的灌溉量不仅削弱了地下水对土壤水的补给，而且多余的灌溉水下渗补给地下水。中子仪和负压计数据表明潜水对土壤的水分分布和土水势分布有很大影响。     

南水北调东线一期工程对梁济运河段地下水影响研究

南水北调东线一期工程建成后,输水期间抬高沿线河水位,河水与地下水补排关系必将发生变化,对河道两侧地下水水位和水量产生一定的影响。根据梁济运河段的地貌、地质和水文地质条件,应用地下水非稳定运动数学模型,研究河渠渗漏对地下水水位的变化,从而分析预测影响区盐渍化情况。梁济运河在南水北调通水后,减小了两岸地下水埋深,影响范围约在500～1000m,地下水埋深减小为1.0～3.0m,地下水埋深均大于适宜临界埋深,但还存在盐渍化的潜在可能性。     

鲁北平原养鸡场周边包气带与地下水砷化合物分布规律

洛克沙胂(3-硝基-4-羟基苯胂酸)被广泛用作饲料添加剂,但大部分以原体形式随粪便排出,进入环境的洛克沙胂在微生物和光照作用下最终转化为毒性较大的As(V)和As(III)等,并在雨水或农灌的淋滤冲积下污染周边土壤、地表水和地下水。以鲁北平原某养鸡场为研究区,对鸡粪、饲料、周边表层土壤、鸡粪堆积和背景包气带垂向剖面以及地下水进行洛克沙胂及其代谢物的检测,结果饲料中洛克沙胂浓度为34mg/kg,鸡粪中HAPA(3-氨基-4-羟基苯胂酸)浓度为11 mg/kg,距离鸡场越近的表层土壤砷含量越高。三个包气带垂向剖面均以As(V)为主,As(III)含量较小。鸡粪堆积处垂向剖面上HAPA、As(V)和As(III)在土壤表层含量最高,浓度随深度增加而呈下降趋势,同时受到土壤岩性的影响,砷化合物主要的吸附层位为0~30cm与200cm以下;背景包气带垂向剖面上各砷化合物含量均明显低于鸡粪堆积处包气带垂向剖面的砷化合物含量;在鸡场内旧井中检测到浓度为165μg/kg的As(V)。结果证实鸡粪堆积导致土壤包气带、周边土壤和地下水砷含量增加,且这种污染很难消除。     

非饱和带土壤水分势能与水分运动

本文通过对非饱和带水分势能的研究,阐述了土壤水分势能的变化与水分运动的关系,分析了“零通量面”的产生发展及其在研究土壤水分运动中起到的作用     

Assessment of Capillary Rise from Shallow Groundwater by the Simulation Model SIMWASER Using Either Estimated Pedotransfer Functions or Measured Hydraulic Parameters

The performance of the water balance and crop growth model SIMWASER to estimate the water supply of a lawn by capillary rise from shallow ground water was investigated by using lysimeter measurements with a sandy and a clayey soil. Moreover the robustness of the model was evaluated by running it either with measured hydraulic soil parameters or with estimated pedotransfer functions (PTFs) derived from texture and bulk density. Simulations were performed for the years 1996–1998 with input data from the lysimeter station Berlin-Dahlem (Germany) for lysimeters containing undisturbed sandy or clayey soil monoliths, with groundwater at 135 cm depth. Simulated evapotranspiration and percolation/capillary rise were in good agreement with the measured data for all variants, while simulated soil water storage was acceptable only for the variants using hydraulic soil data based on laboratory measurements or using PTFs derived from known soil class and bulk density. PTFs based on mean total pore volume of the respective soil classes yielded soil water storages which were evidently too high; therefore they should be used with care and must be avoided at all in simulating the soil water balance of arid sites with shallow groundwater.     

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。     

TRANSIENT FLOW DRAINAGE EQUATIONS CONSIDERING BOTH DELAYED GRAVITY RESPONSE AND EVAPORATION FROM WATER TABLE

The drainable porosity is one of the important parameters in the unsteady drainage formulas. Due to delayed gravity response the drainable porosity is a function of the rate of drawdown and the depth of water table. The evaporation from groundwater plays an important role in lowering water table, in drainage design formulas it should be taken into account. Drainage equations considering evaporation from groundwater varying with water table depth and evaporation from water surface and involving constant drain-able porosity have been proposed by many authors. In this paper new formulas considering both delayed gravity yield and evaporation as a function of water table depth are developed and verified by experimental data.     

Method of coupling 1-D unsaturated flow with 3-D saturated flow on large scale

A coupled unsaturated-saturated water flow numerical model was developed. The water flow in the unsaturated zone is considered the one-dimensional vertical flow, which changes in the horizontal direction according to the groundwater table and the atmospheric boundary conditions. The groundwater flow is treated as the three-dimensional water flow. The recharge flux to groundwater from soil water is considered the bottom flux for the numerical simulation in the unsaturated zone, and the upper flux for the groundwater simulation. It connects and unites the two separated water flow systems. The soil water equation is solved based on the assumed groundwater table and the subsequent predicted recharge flux. Then, the groundwater equation is solved with the predicted recharge flux as the upper boundary condition. Iteration continues until the discrepancy between the assumed and calculated groundwater nodal heads have a certain accuracy. Illustrative examples with different water flow scenarios regarding the Dirichlet boundary condition, the Neumann boundary condition, the atmospheric boundary condition, and the source or sink term were calculated by the coupled model. The results are compared with those of other models, including Hydrus-1D, SWMS-2D, and FEFLOW, which demonstrate that the coupled model is effective and accurate and can significantly reduce the computational time for the large number of nodes in saturated-unsaturated water flow simulation.     

不同潜水埋深条件下的农田土壤水分动态试验研究

不同潜水埋深下玉米田土壤水分动态表现为:该区玉米田土壤水分的季节性变化可划分为3个阶段:春季缓慢失墒期(4~6月)、雨季干湿交替期(7~8月)、稳墒恢复期(9月)。地下水埋深愈浅,相同层次土壤含水率愈高。当地下水埋深较大时,0.6m以下土层含水率呈现明显的分层分布状态,表层受地下水补给的水量已大大减小,其降低的程度主要与各层次土壤的持水特性有关。     

ESTIMATION OF WATER TABLE ELEVATION BY UNIVERSAL COKRIGING

When water resource or quality problems assoelated with phreatic water in geological settings are studied,information about water table elevations is often crucial. In those eases where the water table is a subdued replica of the ground surface, universal cokriging can be used to estimate water table elevations at un sampled locations on the basis of water table and ground surface elevation measurements obrained at well locations. In this paper, universal cokriging,with ground surface elevation considered as a co variate, was used to estimate water table elevations. Universal cokriging equations were derived, an iterative method for obtaining experimental variograms was established, and a ease study of an initial groundwater flow simulation in the Xiuwu County,Henan Province, China, was presented. In the ease study,the initial groundwater flow regime was represented both by universal cokriging with the ground surface elevation serving as a covariate and by universal kriging without the inclusion of ground surface elevation as a covariate. A comparison of the results from these two approaches shows that groundwater levels of phreatic water at locations without measurements in regions with unconsolidated porous media can be estimated more accurately by universal cokriging.     

浅地下水埋深区潜水对SPAC系统作用初步研究

在地下水埋深较浅的地区，潜水参与和影响了SPAC系统的水分、生物、化学等过程。禹城综合试验站和南通农水科研站试验结果表明，潜水对土壤－植物－大气连续体的水分过程和生物过程都有着显著的作用。禹城试区1998年玉米灌浆期腾发量的15.69%是由地下水蒸发“贡献”的；南通农水站试验表明，潜水通过控制土壤水分分布影响冬小麦根系发育和冬小麦产量，统计结果显示：对于冬小麦，在没有灌溉的条件下，存在着一个最优地下水位埋深，约在1.5m左右。研究成果对于深入分析水系统水分运移规律和充分利用地下水、制定合理的节水灌溉方案以及通过控制地下水对农作物生长进行调控等有着一定的理论价值和生产意义。