Groundwater solute chemistry,hydrogeochemical processes and fluoride contamination in phreatic aquifer of Odisha,India

The work investigates the major solute chemistry of groundwater and fluoride enrichment(F^(-))in the shallow phreatic aquifer of Odisha.The study also interprets the hydrogeochemical processes of solute acquisition and the genetic behavior of groundwater F^(-)contamination.A total of 1105 groundwater samples collected from across the state from different hydro-geomorphic settings have been analyzed for the major solutes and F^(-) content.Groundwater is alkaline in nature(range of pH:6.6-8.7;ave.:7.9)predominated by moderately hard to very hard types.Average cation and anion chemistry stand in the orders of Ca^(2+)>Na^(+)>Mg^(2+)>K^(+) and HCO_(3)^(-)>Cl^(-)>SO_(4)^(2-)>CO_(3)^(2-) respectively.The average mineralization is low(319 mg/L).The primary water types are Ca-Mg-HCO_(3) and Ca-Mg-Cl^(-)HCO_(3),followed by Na-Cl,Ca-Mg-Cl,and Na-Ca-Mg-HCO_(3)^(-)Cl.Silicate-halite dissolution and reverse ion exchange are the significant processes of solute acquisition.Both the geogenic as well as the anthropogenic sources contribute to the groundwater fluoride contamination,etc.The ratio of Na^(+)/Ca^(2+)>1.0 comprises Na-HCO_(3)(Cl)water types with F^(-)>1.0 mg/L(range 1.0-3.5 mg/L)where the F^(-)bears geogenic source.Positive relations exist between F^(-)and pH,Na^(+),TDS,and HCO_(3)^(-).It also reflects a perfect Na-TDS correlation(0.85).The ratio of Na^(+)/Ca^(2+)<1.0 segregates the sample population(F^(-)range:1.0-4.0 mg/L)with the F derived from anthropogenic sources.Such water types include Ca-Mg-HCO_(3)(Cl)varieties which are recently recharged meteoritic water types.The F^(-) levels exhibit poor and negative correlations with the solutes in groundwater.The Na-TDS relation remains poor(0.12).In contrast,the TDS levels show strong correlations with Ca^(2+)(0.91),Mg^(2+)(0.80)and even Cl^(-)(0.91).The majority of the monitoring points with the anthropogenic sources of groundwater F^(-) are clustered in the Hirakud Canal Command area in the western parts of the state,indicating the role of irrigation return flow in the F^(-) contamination.

Analysis of phreatic evaporation law and influence factors of typical lithology in Hebei Plain

Based on three typical mediums(sandy loam, loam and sandy clay loam) in Hebei Plain, this paper designs phreatic evaporation experiments under different lithology and phreatic depth. Based on the analysis of experimental data, the phreatic evaporation law and influencing factors of three mediums were studied. The results showed that:(1) The shallower the phreatic depth, the larger the phreatic evaporation.(2) Sandy clay loam has the biggest response to the increase of the phreatic depth, sandy loam is the second and loam is the smallest.(3) The limit depth of phreatic evaporation of sandy clay loam is about 3 m and that of loam and sandy loam is about 2 m and 3 m, seperately.(4) By fitting the daily evaporation of phreatic water and phreatic depth, the results showed that sandy loam and sandy clay loam are exponential functions and loam is power functions.

Analytic solution of phreatic surface in the slope of reservoir bank

In most cases, the slope stability of reservoir bank is analyzed on the premise that the location of phreatic surface is obtained. But many designers generalize a line as the phreatie surface through their experience to analyze the stability, which is unsafe in the project. To find a solution of the phreatic surface which is convenient to put into use and in accordance with the practice, the article, based on Boussinesq equation, infers analytic solutions suitable to the water level at different ratios and achieves an analytic solution equation through fitting curves. The correctness of the equation is also proved by the experiments of sand and sand-clay models and the inaccuracy of empirical generalization is analyzed quantitatively. The calculation results show that the inaccuracy through the method of experiential generalizing is so large that the designers should be awake to it.

Analysis of evaporation of high-salinity phreatic water at a burial depth of 0 m in an arid area

High-salinity phreatic water refers to which with total dissolved solids（TDS）>30 g/L. Previous studies have shown that high salinity phreatic water evaporation is different at different depths. High salinity phreatic water evaporation under 0 m depth is the basis of the high salinity phreatic water evaporation studies. In this study, evaporation of high-salinity phreatic water at a burial depth of 0 m in arid area was investigated. New insights were gained on evaporation mechanisms via experiments conducted on high-salinity phreatic water with TDS of 100 g/L at 0 m at the study site at Changji Groundwater Balance Experiment Site, Xinjiang Uygur Autonomous Region in China, where the lithology of the vadose（unsaturated zone） was silty clay. Comparison was made on the data of high-salinity phreatic water evaporation, water surface evaporation(EΦ20) and meteorological data obtained in two complete hydrological years from April 1, 2012 to March 31, 2014. The experiments demonstrated that when the lithology of the vadose zone is silty clay, the burial depth is 0 m and the TDS is 100 g/L, intra-annual variation of phreatic water evaporation is the opposite to the variation of atmospheric evaporation EΦ20 and air temperature. The salt crust formed by the evaporation of high-salinity phreatic water has a strong inhibitory effect on phreatic water evaporation. Large volumes of precipitation can reduce such an inhibitory effect. During freezing periods, surface snow cover can promote the evaporation of high-salinity phreatic water at 0 m; the thicker the snow cover, the more apparent this effect is.

Specific yield of phreatic variation zone in karst aquifer with the method of water level analysis

Regime of groundwater level is a comprehensive reflection of the hydrogeological environment from the perspective of groundwater. Based on the analysis of the water-level change of 65 groundwater monitoring points from 1987 to 1990, it is found that intermittent cones of depression came into being due to groundwater exploitation in Guilin during the observation period. The buried depth of groundwater in the drawdown cones, the annual variation of water level and specific yield have higher values. Improvement has been made to the formula of infiltration coefficient of precipitation. By using the precipitation response data recorded at every 15 minutes for water level of No. 9 borehole which is near Zengpiyan Cave, the specific yield of phreatic variation zone is indirectly calculated by using the modified formula. The results are range from 0.012 to 0.462 and the spatial distribution of specific yield is ascertained. These make up the deficiency that empirical values cannot be categorized based on the actual conditions. What’s more, the widely used Aviriyanover’s empirical formula is poorly applicable to karst area. This is due to its strict requirement for outside conditions, such as shallow buried depth, homogeneous aquifer medium and small hydraulic gradient.

Effect of climate change on the trends of evaporation of phreatic water from bare soil in Huaibei Plain, China

When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change.

RULE OF TRANSIENT PHREATIC FLOW SUBJECTED TO VERTICAL AND HORIZONTAL SEEPAGE

In a semi-infinite aquifer bounded by a channel, a transient flow model is constructed for phreatic water subjected to vertical and horizontal seepage. Based on the first linearized Boussinesq equation, the analytical solution of the model is obtained by Laplace transform. Having proven the transformation between the analytical solution and some relevant classic formulas, suitable condition for each of these formulas is demonstrated. On the base of the solution, the variation of transient flow process caused by the variables, such as vertical infiltration intensity, fluctuation range of river stage, aquifer parameters such as transmissivity and specific yield, and the distance from calculating point to channel boundary, are analyzed quantitatively one by one. Lagging effect will happen to the time, when phreatic water gets its maximum fluctuation velocity, response to the varying of the variables stated above. The condition for some variables to form equivalent lagging effect is demonstrated. Corresponding to the mathematical charac teristics of the analytical solution, the physical implication and the fluctuation rule of groundwater level are discussed.

Comparing phreatic evaporation at zero water table depth with water surface evaporation

Salt-affected soils are mostly found in irrigated areas within arid and semi-arid regions where the groundwater table is shallow.Soils of this type have become an increasingly severe problem because they threaten both the environment and the sustainable development of irrigated agriculture.A tool to estimate phreatic evaporation is therefore urgently required to minimize the salinization potential of salt-affected areas.In this context,phreatic evaporation at zero water table depth(E0)is a key parameter for establishing a model for calculating phreatic evaporation.The aim of this study was to explore the law of phreatic evaporation and to develop structurally rational empirical models for calculating phreatic evaporation,based on E0data of six types of soil(i.e.,gravel,fine sand,sandy loam,light loam,medium loam,and heavy loam)observed using the non-weighing lysimeter and water surface evaporation(E601)data observed using a E601 evaporator of same evaporation area with a lysimeter-tube at the groundwater balance station of the Weigan River Management Office in Xinjiang Uygur Autonomous Region,China,during the non-freezing period(April to October)between 1990 and 1994.The relationship between E0and E601was analyzed,the relationship between the ratio of E0to E601and the mechanical compositions of different soils was presented,and the factors influencing E0were discussed.The results of this study reveal that E0is not equal to E601.In fact,only values of the former for fine sand are close to those of the latter.Data also show that E0values are related to soil texture as well as to potential atmospheric evaporation,the ratio of E0to E601and the silt-clay particle content(grain diameter less than 0.02 mm)is negatively exponentially correlated,and that soil thermal capacity plays a key role in phreatic evaporation at E0.The results of this analysis therefore imply that the treatment of zero phreatic depth is an essential requirement when constructing groundwater balance stations to study the law of phreatic evaporation.

Stable Isotopes and Chloride Applied as Soil Water Tracers for Phreatic Evaporation Experiment

A phreatic water evaporation experiment,without rainfall influence,was designed to study the mechanisms of soil water movement through groundwater recharge to the unsaturated zone. Soil moisture content,chloride concentration,and δD and δ~18 O values of soil water were measured. Results showthat with decreasing soil moisture content,the chloride concentration of leachate( ρ_f(Cl)) in the capillary water layer decreases,whereas the ρ_f(Cl) value of the hanging and film water layers above the capillary water layer increases. With the combined δD and δ~18 O values,the soil water in the hanging and film water layers is influenced by evaporation,although a dry sand layer of 39 cm exists above the wet sand layer. The highest evaporation rate and the largest salt accumulation occur at a depth of about 39 cm in columns d,e,and f(Six polyvinyl chloride columns were assigned as column a,b,c,d,e,and f). We deduce that soil water migrates in the form of liquid water above the capillary water layer. In the experiment,a part of phreatic water consumed is used for the movement of soil water,whereas the other part is lost to evaporation. Soil water could continue migrating upward with prolonged experiment duration.

A GIS-Based DRASTIC Model for Assessing Phreatic Aquifere of Bekalta (Tunisian Sahel)

The phreatic aquifer of Bekalta experienced a progressive degradation of water resources over time: using increasingly important waters for irrigation and drinking water, nitrate pollution, salinization... This aquifer is of great economic importance because it is used for irrigation and domestic consumption. Vulnerability map to nitrate pollution is a necessary tool to developing management to preserve the quality of groundwater. This study utilized the Geographic Information System technique and the DRASTIC model to assess the vulnerability of groundwater resources to contamination. The Geographic Information System (GIS) technology represents the best method to solve the main problems in the vulnerability survey. Indeed is allowed for swift organisation, quantification, and interpretation of large volumes of hydrological data with computer accuracy and minimal risk of human errors. The Visio model was exported and loaded into an ESRI Geodatabase in ArcCatalog as defined by the UML model. The purpose of this geodatabase is data harmonization process within modeling groundwater vulnerability to pollution. The resulting map shows evidence for three categories of vulnerability (low, middle and high). The resultant vulnerability map showed the predominant of moderately vulnerability class on the most of the Bekalta region which occupying an area of 68%. The low and high groundwater vulnerability classes occupy respectively an area of 30% and 2% of the total surface of the study area.

抽水过程中井水位变化的分形特征研究

【目的】探讨潜水井抽水过程中井水位与井流量变化的分形特征,为潜水井水位与井流变化的定量研究探索新的计算途径。【方法】在引入分形理论、分形维数计算方法的基础上,以潜水含水层抽水过程为例,计算了主井和各观测井水位及井流量过程线的分形维数和曲率大小。【结果】将分形维数与不同落程井流量大小加以比较,可以发现分形维数D越大,观测井水位变化过程线越复杂,形状因子a越大,曲线越扁平,曲线峰值越小;不同落程井流量的大小与其对应井流量过程线的分形维数大小呈负相关。【结论】分形理论中的分形维数D和形状因子a,可以定量描述潜水井抽水过程中井水位过程线的分形维数和形状因子的复杂关系。

定流量下潜水非完整井稳定流计算方法

针对现有潜水非完整井对于不同的管长和淹没状态下有着4种完全不同的理论计算公式,不能很好地解决实际工程中由于潜水位降深不断变化而引起的流量变化问题,将潜水含水层沿潜水位最大降深处分成上下两部分,采用积分变换方法,推导得到可适用于不同管长和淹没状态下的定流量潜水层非完整井的稳定流公式;然后在此基础上,采用Delphi结合Matlab自行开发一个计算程序,对潜水非完整井的井流特点进行分析;最后通过一个基坑降水算例说明了其应用于实际工程的有效性。研究结果表明:①推导得到的潜水非完整井公式可以退化为经典的潜水完整井裘布依公式,并在特殊情况下可得到近似解析解;②自行开发的计算程序可对不同条件下潜水非完整井的阻力系数和流量进行自动快速计算,为潜水非完整井的井流性状分析提供了便利的工具;③将推导出的潜水非完整井稳定流计算公式应用于有隔水围护结构且采用坑内降水方式的基坑工程是可行的。

徐州张集水源地浅层地下水动态及其对不同开采方案响应

张集水源地是徐州市一个拟建水源地。了解浅层地下水动态变化规律是设计水源地最优取水方案、满足当地居民生活及工农业生产需水和水源地环境保护的重要前提条件之一。分析了水源地在现状以及不同开采条件下浅层地下水动态影响因素,建立了三维等参有限元数学模型模拟水源地地下水运动规律,利用大型群孔抽水试验资料进行参数识别和模型校正,预报了不同开采方案对水源地浅层地下水动态的影响,结果表明:水源地开采后,水源地开采将成为浅层地下水动态的主要影响因素之一;水源地允许开采量为13.71万m^3/d是适合的,它不会引起地下水位的持续下降,不仅可满足当地居民用水需求,而且可以向徐州市稳定供水。

富水厚砂层斜井施工阶梯降水方法研究

为了有效解决富水厚砂层斜井施工过程中地下水问题,基于潜水完整井降水理论,参考深基坑"大井法"降水方法,提出了潜水完整井大井法斜井阶梯降水基本理论,得到了降水单元流量与布置间距的关系。用此理论指导薛庙滩矿井二号缓坡副斜井降水施工,结果表明:降水后地下水位沿斜井方向逐渐降低,均在斜井底板安全距离以下;使斜井井筒能够用传统方法掘进,降低工程造价与施工难度。

深圳典型潜水地层地铁车站基坑降水引起水位变化机理的试验研究

以深圳某地铁车站基坑工程为背景,进行基坑不完整井降水模型试验。结果表明:在降水条件相同的情况下,由于绕渗作用的影响,基坑内降水有效影响深度大于基坑外;由于群井效应的影响,基坑内双井降水有效影响深度大于单井降水;在地连墙深度范围内,基坑外土层中孔隙水压变化值随深度的增加而增大,基坑内不完整井降水引起基坑外降水曲线为"先下凹再上凸"型。基于巴布什金潜水层完整井和不完整井涌水量理论计算公式,推导不完整井降水有效影响深度计算公式。基于模型试验数据,通过曲线拟合得到基坑外降水曲线方程。以实际基坑工程为案例,将采用理论计算公式计算得到的基坑内不完整井降水有效影响深度和基坑外降水曲线与数值模拟结果进行对比,发现有效影响深度误差较小,降水曲线基本吻合,从而验证了理论计算公式的正确性和合理性。

黄土潜水含水层深井抽水时水跃值变化特性

水跃值的变化比较复杂,与抽水井深度、半径、井出水量以及抽水持续时间等因素有关,其中井出水量影响最大。本文根据抽水试验资料总结了黄土潜水井水跃值的变化规律并分析了其成因;总结了水位降深随抽水时间的变化关系,并建立了经验公式;提出了公式中参数的确定方法。

地下水污染监测井布设方案研究

为保护地下水资源,工业项目建设过程中需要制定出合理的地下水污染监控方案。特别是在地下水系统比较脆弱的低丘区,其松散层发育较薄,极易造成地下水污染。以某工场项目为例,利用水质模拟模型,模拟出该项目在非正常工况下可能污染物下渗到地下水系统中的运移扩散规律,并根据模拟结果制定出合理的观测井布设方案和监测频率。

黄土潜水层深井降水三维有限元模拟研究

视抽水井为定流量边界,并假定流量沿井壁的分布是均匀的,在此条件下建立了黄土厚潜水层深井抽水时的三维渗流模型,并用C++语言编制了三维有限元程序,计算了单井抽水、双井抽水时水位随时间的变化规律,计算结果与观测结果误差较小。另计算了少陵塬隧洞第一期降水方案的降水效果,表明其不能满足施工进度的要求,并对此方案作了修改,在后期施工中取得了良好的降水效果。

潜水含水层中的非完整井降水设计计算探讨

通过对潜水含水层中的非完整井基坑涌水量计算方法的分析 ,探讨引入抽水“有效带”的概念 ,将非完整井群涌水量计算转化为等效完整井群涌水量计算方法的可行性及由此产生的相对误差大小。通过几个实例计算表明 ,简化方法一般可将基坑涌水量计算误差控制在 2 0 %以内 。