A computer method based on simulated annealing to identify aquifer parameters using pumping‐test data

Conventional graphical or computer methods for identifying aquifer parameters have their own inevitable limitations. This paper proposes a computer method based on a drawdown model and a heuristic approach of simulated annealing (SA) to determine the best‐fit aquifer parameters of the confined and unconfined aquifer systems. The drawdown model for the confined aquifer is the Theis solution and the unconfined aquifer is the Neuman solution. The estimated results of proposed method have better accuracy than those of the graphical methods and agree well with those of the computer methods based on the extended Kalman filter and Newton's method. Finally, the sensitivity analyses for the control parameters of SA indicate that the proposed method is very robust and stable in parameter identification procedures. Copyright © 2007 John Wiley & Sons, Ltd.     

Use of deuterated water as a conservative artificial groundwater tracer

Conservative tracers are necessary to obtain groundwater transport velocities at the field scale. Deuterated water is an effective tracer for this purpose due to its similarity to water, chemical stability, non-reactivity, ease of handling and sampling, relatively neutral buoyancy, and reasonable price. Reliable detection limits of 0.1 mg deuterium/L may be obtained in field tests. A field example is presented in which deuterated water, bromide, and pentafluorobenzoic acid are used as groundwater tracers. Deuterated water appeared to be transported conservatively, producing almost identical breakthrough curves as that of other soluble tracers. Electronic Publication     

利用观测孔中地下水位潮汐效应计算天津滨海新区含水层参数

在沿海地区,尤其是围海造陆工程形成的陆域地区地下水水位受潮汐影响较大,使传统水文地质试验求取含水层参数存在较大误差。因此通过合理概化地下水在潮汐作用下运动规律,建立数学模型,推导解析公式求取沿海含水层参数具有重要意义。分析天津滨海新区两处观测孔地下水位及潮汐波动特征,在滞后时间不明显的情况下,利用观测孔水位变幅数据计算了含水层水头扩散系数,并根据承压含水层储水系数经验值进一步获得含水层渗透系数。通过两个观测孔分别计算,对比计算结果互相验证发现,该方法取得了令人满意的结果。利用地下水潮汐效应计算含水层参数可以广泛应用于沿海地区水文地质工作中。     

Great tritium ages explain the occurrence of good-quality groundwater in a phreatic aquifer of an urban area, Lublin, Poland

The phreatic aquifer of the Lublin chalk in the watershed of the Bystrzyca River, eastern Poland, is characterized by waters of good quality. Its hydraulic conductivity is related to a fissure network of low porosity, as much as 0.006 at the outcrops. The good quality of water in this urban setting is surprising because, according to estimates based on Darcy's law, a high seepage velocity would be expected, resulting in rapid transport of pollutants in the aquifer. However, tritium sampling reveals that the mean ages range from about 55 to 92 years in four cases, and about 250 to 350 years in 11 cases. One sampling site is free of tritium, which indicates an even greater age. Such great ages can be explained only by a retardation of solute transport due to matrix diffusion, that is, an exchange between mobile water in the fissures of low porosity and stagnant water in the matrix of high porosity. The delay factor is given as the ratio of total porosity to fissure porosity. In consequence, all types of dissolved constituents and, to some degree, fine suspended matter are delayed in their transport to springs and wells. In addition, non-conservative constituents have longer times to sorb, react, and decay than in the case of transport without a dominant influence of matrix diffusion. Though pollutants are greatly delayed, their accumulation in the matrix and slow diffusion into the fissures contribute to their persistence in groundwater. Regional values of hydraulic conductivity, estimated from tritium ages and known matrix porosity, agree reasonably well with the values known from pumping tests, which supports the interpretation of a dominant influence of matrix diffusion on solute transport. Electronic Publication     

Complementary use of tracer and pumping tests to characterize a heterogeneous channelized aquifer system in New Zealand

The combined use of pumping and tracer test data enabled the derivation of equivalent average hydraulic conductivities (K_avg) for each test in a heterogeneous channelized alluvial aquifer, whereas K values of the preferential flow paths were two orders of magnitude higher. Greater and earlier drawdown was generally observed along preferential flow lines in a pumping test, within an array of 21 wells. The study aim was to characterize hydraulic properties of a channelized aquifer system in New Zealand by combining tracer and pumping test data. Estimates were able to be made of the percentage of highly permeable channels within the profile (～1.2%), effective porosity that reflected the maximum fraction of highly permeable channels within the aquifer (?_eff–pc ～0.0038), and flows through highly permeable channels (～98%) and the sandy gravel matrix material (～2%). Using ?_eff–pc, a tracer test K_avg value (～93 m/day) was estimated that was equivalent to pumping test values (～100 m/day), but two orders of magnitude smaller than K calculated solely from transport through permeable channels (K_pc ～8,400 m/day). Derived K values of permeable and matrix material were similar to values derived from grain size distribution using the Kozeny-Carman equation.     

横河煤矿底含放水孔与井田内供水井连通试验研究

在邹城市宏河矿业集团横河煤矿井田范围内,有多眼供水井.由于这些供水井大部分穿透了第四系松散层,致使上部含水层和底部含水层串通,造成对矿井水的补给.但较长时期以来,由于缺乏直接的证据,对供水井与煤矿底含涌水之间的关系看法不一,从而造成对矿井水防治决策的困扰.通过化学示踪法跟踪地下水的流向,证实是供水井自身结构串通了第四系含水层上、中、下组,从而造成上组含水层对底部含水层的补给.     

振荡试验确定倾斜承压含水层水文地质参数

为评价振荡试验在获取倾斜承压含水层水文地质参数过程中含水层倾角对计算结果的影响,基于Kipp模型推导了考虑承压含水层倾角的振荡试验解析解模型。倾斜承压含水层量纲一贮水系数和量纲一导水系数不变条件下,测试井-含水层系统的量纲一阻尼系数随着倾角的增加而增加。修正模型计算的量纲一阻尼系数与Kipp模型计算的量纲一阻尼系数偏差10%以上时,必须考虑倾角的影响并且承压含水层倾角对水头响应曲线造成影响临界角度约为34°。修正模型和Kipp模型对现场振荡试验水头响应曲线分析结果的差异表明,忽略含水层倾角会对倾斜承压含水层导水系数和贮水系数的计算结果产生较大误差。     

Field tracer test for denitrification in a pyrite-bearing schist aquifer

A small-scale artificial tracer test performed on a schist aquifer in Brittany has helped clarify mechanisms and kinetics of in situ autotrophic denitrification. NO₃ was injected as a pulse simultaneously with a conservative tracer -Br⁻. During the test, which lasted 210 h, 73% of the injected Br⁻ was recovered, as against only 47% of the NO₃. The 26% difference in the recovery of the two injected species is interpreted as being the result of denitrification, in part due to the direct oxidation of pyrite present in the solid aquifer according to the reaction: 5FeS₂+14NO₃⁻+4H⁺→7N₂+10SO₄²⁻+5Fe²⁺+2H₂O, and in part due to subsequent iron oxidation according to the reaction: NO₃⁻+5Fe²⁺+6H⁺→1/2N₂+5Fe³⁺+3H₂O. Despite the potential increase in SO₄ and Fe resulting from denitrification through pyrite oxidation, the concentrations of these elements in the groundwater remain moderate due to the precipitation of minerals such as jarosite and/or natroalunite. Tracer transfer takes place in a heterogeneous medium which, according to the breakthrough curves, can be simplified to a dual-porosity aquifer comprising a high-permeability (fractures or large fissures) medium of low porosity from which only minor denitrification of circulating NO₃-bearing water was observed and a low-permeability (small fissures) medium of high porosity which induces a higher denitrification rate in the circulating NO₃-bearing water. The kinetics of the denitrification reaction are high compared with results obtained for other environments and can be described by a first-order model with a half life of 7.9 days for the low-porosity medium and only 2.1 days for the high-porosity medium.     

分析隔水边界附近抽水-恢复试验数据的新方法

为能同时分析含水层具有直线隔水边界条件下,抽水试验中抽水―恢复阶段降深数据,提出了一种新的数据分析方法。在建立这种方法时,将表示抽水和恢复阶段水头降深表达式中Theis井函数的级数表达式的前3项作为其近似表达式,经过推导,分别得到抽水和恢复2个阶段的直线方程。2个直线方程的因变量和自变量均为观测数据的函数,而直线常数为待求参数的函数,在进行数据分析时,只要将试验观测数据分别转化为直线方程的因变量和自变量数据,就能够利用一元线性回归法分别计算2个直线方程的常数,而利用直线常数的表达式,能够推导得到计算含水层参数和映射井到观测孔间距离的公式。通过算例说明了方法的具体应用步骤。     

沉积物和悬浮颗粒物在岩溶水系统污染物衰减与运移中的作用

本文讨论了沉积物和悬浮颗粒物/胶体在岩溶水系统污染物衰减与运移中的作用,介绍了关于瑞士某岩溶水系统内颗粒物与微生物污染间关系的实验结果。该实验场包括一个接纳农田排水的落水洞及与其相连的两个泉,其中一个泉是供水水源地。利用便携式粒子计实时监测泉水中颗粒分布的变化情况,同时对浊度、总有机碳和其它参数进行连续监测;并对水中E型大肠菌群进行了分析。在暴雨过后,观测到了浊度的两种不同表现:即泉排泄量增加时,浊度最初表现为脉状水动力条件下岩溶系统内沉积物的二次运移;几天后观测到的浊度则表明水已从落水洞到了泉口,常常具有高的总有机碳、硝酸盐及E型大肠菌群。颗粒分布分析结果差异更大:早期的浊度是不同粒径颗粒物的混合,而后期的浊度更多是由较细颗粒构成,因为大颗粒物已沉积在落水洞到泉口之间的岩溶系统内。E型大肠菌群与0.9～1.5 μm颗粒物之间具有很好的相关性。因而较细颗粒的相对增加可应用于微生物污染 “早期预报系统”。除了水污染,颗粒分还可以帮助我们研究岩溶环境的其它问题,如土壤侵蚀。      

基于高分辨率示踪技术的岩溶隧道涌水来源识别及含水介质研究

利用高分辨率示踪技术探讨了重庆三泉隧道突水来源,并对含水介质进行了刻画,结果表明:（1）隧道涌水段受长滩地下河影响,而麦阴槽落水洞为长滩地下河的补给来源之一;（2）试验段岩溶含水介质通畅,地下水流速快,为典型紊流态;地下河管道结构不均匀,发育两条过水通道,为主管道并联支管道,无溶潭和地下湖发育;利用Qtracer2软件,计算得到地下河几何参数及水文地质参数:地下管道储水体积为1 148.4 m3,表面积为1.30×106 m2,平均直径为1.37 m,长度为780 m;摩擦系数为0.51,舍伍德数为1 055.1,施密特数为1 140,水力深度为1.08 m,分子扩散边界层厚度为1.3 mm;（3）因试验时间短、试验为小流量期及存在其他地下河出口等条件制约,示踪剂天来宝的回收率较低,上湾洼地与隧道涌水段连通关系有待进一步研究;（4）由于三泉隧道涌水点与地表水具有直接水力联系,且涌水量大,建议引走地表洼地水源、填埋隧道上方麦阴槽落水洞或在隧道下方新建泄水洞排水。      

利用滨海地下水潮汐效应估计含水层参数:以北海半岛为例

通过分析滨海含水层中观测孔的水位动态资料,确定含水层的水力性质和某些参数,或推测含水层在海底的延伸长度和露头处是否存在覆盖层,是水文地质学家一直很感兴趣的问题之一。文中充分分析了广西北海半岛滨海地区水文地质条件,将研究区第一个承压含水层系统概化为具有上覆弱透水层越流和含水层海底露头覆盖层的垂向三层结构的不稳定流模型。应用该模型的解析解对广西北海半岛滨海含水层系统的观测数据进行了分析,拟合效果很好,并利用最小平方罚函数法估算了研究区含水层的参数。     

示踪试验在岩溶大泉修复中的应用——以丽江黑龙潭为例

为查明云南丽江黑龙潭泉域九子海洼地补给区地下水与周边泉水的连通关系,提供泉水修复的科学依据,采用人工化学示踪方法,选取碘化钾作为示踪剂,开展了一次大型地下水示踪试验。根据试验数据计算地下水渗流速度,并分析黑龙潭泉域地下水系统结构特征。结果表明:九子海洼地补给区地下水与黑龙潭泉群和古城泉群具有显著的连通关系,与清溪泉群和白浪花泉群不存在连通关系,九子海至黑龙潭和古城的地下水渗流速度分别为405.86~1 077.84 m·d-1、349.96~629.09 m·d-1。九子海洼地为黑龙潭泉域地下水系统的主要补给区,同时也可作为黑龙潭泉水修复的有效注水点,接受补给后,主要通过深层岩溶管道向南运移至黑龙潭—古城方向,其中黑龙潭泉群为系统的排泄天窗。      

A novel analytical solution for constant‐head test in a patchy aquifer

A mathematical model describing the hydraulic head distribution for a constant‐head test performed in a well situated at the centre of a patchy aquifer is presented. The analytical solution for the mathematical model is derived by the Laplace transforms and the Bromwich integral method. The solution for the hydraulic head has been shown to satisfy the governing equations, related boundary conditions, and continuity requirements for the hydraulic head and flow rate at the interface of the patch and outer regions. An efficient numerical approach is proposed to evaluate the solution, which has an integral covering an integration range from zero to infinity and an integrand consisting the product and square of the Bessel functions. This solution can be used to produce the curves of dimensionless hydraulic head against dimensionless time for investigating the effect of the contrast of formation properties on the dimensionless hydraulic head distribution. Define the ratio of outer‐region transmissivity to patch‐region transmissivity as α. The dimensionless hydraulic head for α=0.1 case is about 2.72 times to that for α=10 case at dimensionless large time (e.g. τ?10⁶) when the dimensionless distance (ρ) equals 10. The results indicate that the hydraulic head distribution highly depends on the hydraulic properties of two‐zone formations. Copyright © 2006 John Wiley & Sons, Ltd.     

Assessing aquifer susceptibility to and severity of atrazine contamination at a field site in south-central Wisconsin, USA

 A field study from October 1989 through July 1992, conducted on a 4.1-km² area in south-central Wisconsin, USA, examined the distributions of atrazine and its chlorinated metabolites in groundwater and related those distributions to the groundwater flow system. MODFLOW and PATH3D were used to assess bedrock-aquifer susceptibility to contamination. Estimated travel time from water table to bedrock surface ranges from <0.25 to >512 yr. Spatial distribution of the estimates demonstrates that increased travel time to bedrock can result from the presence of shallow surface-water bodies, greater depths to bedrock, and smaller hydraulic conductivities. Estimated travel times to local domestic wells are inversely related to atrazine and desethylated atrazine concentrations observed in water from those wells. The potential impact of long-term atrazine use on aquifer water quality was investigated using MT3D in two best-case scenarios. Uncertainties associated with predicted atrazine concentrations at various depths and times were estimated. For shallow groundwater, widespread violations of Wisconsin's current preventive action limit were predicted, but with large uncertainty stemming from uncertain estimates of input parameter values. The simulations indicate, however, that moderate inputs at the water table are very unlikely to produce violations of Wisconsin's standards deeper in the aquifer. Received, October 1997 Revised, July 1998 Accepted, July 1998     

Spreading of a NAPL lens in a double-porosity medium

Spreading of a non-aqueous phase liquid (NAPL) denser than water (DNAPL) lens (mound) in the unsaturated zone of double-porosity aquifer above an impervious plane boundary is investigated. The double-porosity aquifer is conceptualized as a fracture network surrounding pervious blocks. Vertical gravity equilibrium is assumed to prevail in each one of the two media, fractures and blocks. Through vertical integration, two coupled partial differential equations for the DNAPL content in each medium are obtained. The mass exchange rate between high- and low-permeability media is considered as a function of NAPL content. The dominant effect is gravity, whereas capillary forces are negligible. Analytical solutions for one-dimensional and axisymmetric problems of mound spreading are obtained.     

Effects of water extraction in a vulnerable phreatic aquifer: Consequences for groundwater contamination by pesticides, Sint-Jansteen area, The Netherlands

Pesticides are a potential threat to the quality of extracted groundwater when the water-supply area is used for agricultural activities. This problem is discussed for the water-supply area of Sint-Jansteen, The Netherlands, where measured pesticide concentrations in the extracted water regularly exceed EU limits (0.1 μg/L). Groundwater samples taken from the aquifer within the water-supply area show low contamination, but samples taken from the extracted water occasionally contain pesticides, making the water inadequate for drinking-water purposes. The more intense contamination of the extracted water is caused by the change in the natural groundwater flow pattern near the extraction wells. In this area, pesticide use cannot be avoided easily, and an approach is given to differentiate pesticide use in the area according to expected travel time toward the wells and the chemical characteristics of the pesticides. A groundwater flow model for the area is developed and the effects of groundwater extraction on the natural flow pattern are evaluated. Using particle tracking, the travel-time zones are determined. Combining these results and the degradation behavior of certain pesticides led to an optimal scheme to integrate agricultural activities and groundwater extraction in the area. This is illustrated for five different types of pesticides (atrazine, simazine, bentazone, MCPA, and mecoprop). Received, October 1998/Revised, July 1999, September 1999/Accepted, November 1999     

On the solutions of modeling a slug test performed in a two-zone confined aquifer

The slug test is a popular field method for estimating aquifer parameters. As a finite-thickness skin is present at a wellbore, the result of test-data analysis may represent average hydraulic properties of the skin and formation zones. Moench and Hsieh (Int. Assoc. of Hydrogeology, The IAH 17th International Congress on Hydrology of Rocks of Low Permeability, Int. Assoc. of Hydrogeology. Tucson, Arizona, 7–12 January) provided the Laplace-domain solution for a confined aquifer with a finite-thickness skin that satisfies the governing equations, boundary conditions, and continuity requirements at the interface of the skin and formation zones. Two new formulae presented here relate the modified zero-order Bessel functions of the first and second kinds to their first and second derivatives. Their solution is evaluated using the modified Crump approach for the Laplace inversion. The numerical values obtained by the modified Crump approach are compared with others based on finite-element modeling. The results indicate that the values based on finite-element modeling exhibit poor accuracy, attributed to errors in the mass balance equation and interface condition in their mathematical model.

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Resumen Los ensayos slug o tipo pulso son métodos populares de campo para estimar parámetros de acuíferos. Debido a que en los sondeos existe una membrana de espesor finito, el resultado del análisis de los datos del ensayo pueden representar las propiedades hidráulicas promedio de las zonas de la formación y dicha membrana. Moench AF y Hsieh PA (Asociación Internacional de Hidrogeólogos, 7–12 Enero 1985) Análisis de datos de prueba slug en un pozo con membrana de espesor finito. 17 Congreso Internacional de la Asociación Internacional de Hidrogeólogos sobre Hidrología de Rocas de Baja Permeabilidad. Asociación Internacional de Hidrogeólogos. Tucson, Arizona. 7–12 Enero. han aportado la solución en el ámbito de Laplace para un acuífero confinado con una membrana de espesor finito que satisface los requerimientos de las ecuaciones dominantes, las condiciones restrictivas, y de continuidad en la interfase de las zonas de formación y membrana. Las dos nuevas fórmulas que se presentan aquí relacionan las funciones modificadas Bessel de orden cero de la primera y segunda clase con su primera y segunda derivadas. Se evalúa su solución usando el enfoque modificado de Crump para la inversión Laplace. Los valores numéricos obtenidos mediante el enfoque modificado de Crump se comparan con otros valores numéricos basados en modelos de elementos finitos. Los resultados indican que los valores basados en el modelo de elementos finitos presentan poca precisión, que se atribuye a errores en la ecuación de balance de masa y a las condiciones de interfase en su modelo matemático.

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Résumé Le slug-test représente une méthode populaire de terrain pour estimer les paramètres d’un aquifère. Du fait de la présence d’une couche à l’épaisseur limitée sur un site de forages, le résultat de l’analyse des données du test pourrait représenté le terrain mais aussi cette couche. Moench AF et Hsieh PA (Association Internationale d’Hydrogéologie, 7–12 Jan 1985) Analyses de données de slug test dans un puits présentant une couche d’épaisseur finie. 17ème congrès international de l’AIH sur l’Hydrologie des roches de faible perméabilité, Association Internationale d’Hydrogéologie. Tucson, Arizona, 7–12 Jan. apportent une solution du domaine de Laplace pour un aquifère confiné avec une épaisseur limitée qui satisfait l’équation en question, les conditions aux limites, et les besoins de continuité à l’interface de la couche et de l’encaissant. Deux nouvelles formules présentées dans cet article met en relation les fonctions de Bessel modifiées d’ordre zéro du premier et second type, avec leur dérivées première et deuxième. Leurs solutions sont évaluées en utilisant une approche de Crump modifiée pour l’inversion de Laplace. Les valeurs numériques obtenues avec l’approche de Crump sont comparées avec d’autres approches utilisant les modèles aux éléments finis. Les résultats indiquent que les valeurs basées sur les modèles aux éléments finis montrent une faible précision, du fait d’erreurs dans le bilan hydrologique et les conditions aux limites dans le modèle.

     

承压含水层非完整反滤回灌井的稳定流计算

反滤回灌井是地下水库中一种有效的回灌设施,它由回灌井和井口反滤层组成。非完整反滤回灌井井流运动由砂反滤层的竖向流和非完整回灌井井流组合而成。文中提出了承压含水层非完整反滤回灌井稳定流的计算方法,分析了反滤层、井损和回灌堵塞等因素对回灌量的影响,并结合实例证明了反滤回灌井回灌量大大低于普通回灌井的回灌量。     

越流区开采条件下承压含水层易污染性机理研究——以单井开采为例

地下水易污染性分析是合理开发利用地下水资源、保护地下水环境的一项重要的基础性工作.长期以来针对潜水含水层易污染性的研究进行的较为深入,而对承压含水层易污染性的研究较为少见.同时,易污染性评价方法又以经验方法为主,受人为主观因素影响较大,因此需要通过对承压含水层污染机理进行研究,以减少人为主观因素对评价结果的影响.本文以单井开采承压含水层为例,通过分析承压含水层受污染的原因,以单位面积上越流补给量占开采量的比重为承压含水层易污染性指数,在建立越流区承压水向完整井稳定运动的微分方程的基础上,得到易污染性指数的解析表达式,并分析了各参数对易污染性的影响,使承压含水层易污染性评价有了一定的理论依据,对合理开发利用承压含水层有一定的指导意义.