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1.
Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany 总被引：1，自引：1，他引：0
Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany)
confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients
of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by
a model that couples the advective–dispersive transport in the fractures with the molecular diffusion exchange in the matrix.
For the scale of the tests (maximum distance of 225 m), an approximation was used in which the influence of adjacent fractures
is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture
approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone
obtained from the tracer tests is about 1.5×10–2 m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10–7 m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity
along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms
the dominant role of the fault zones as collectors of water and conductors of fast flow.
Received, April 1997 Revised, January 1998, August 1998 Accepted, August 1998 相似文献
2.
Lignosulfonate lyes, which had been deposited by a paper factory for about 50 years into Quaternary sediments and accumulated in a quasistagnant depression, became mobile when a depression cone caused by mine activity in a deeper aquifer reached the erosion window close to the disposal site. Their transport parameters in the karstic-fractured-porous carbonate aquifer are shown to be mainly governed by diffusion between the mobile water in karstic channels and fractures and the stagnant water in matrix, although the hydraulic conductivity is shown to depend mainly on the karstic system. The main transport velocity is, with a sufficient accuracy, related to the hydraulic conductivity by a simple model in which matrix porosity is the governing rock parameter. The dispersivity, although also governed by matrix diffusion, depends strongly on several parameters that are difficult to determine. 相似文献
3.
Rock and flow parameters of three karstic-fissured-porous aquifers in the Krakow-Silesian Triassic formations were measured
using various methods and compared. Though cavern and fissure porosities are shown to be very low (cavern porosity below 0.5%
and fracture porosity below 0.2%), they contribute dominantly to the hydraulic conductivity (from about 1.3×10–6 to about 11×10–6 m/s). Matrix porosity (2–11%) is shown to be the main water reservoir for solute transport and the main or significant contributor
to the specific yield (<2%). Though the matrix porosity is shown to be much larger than the sum of the cavern and fissure
porosities, its contribution to the total hydraulic conductivity is practically negligible (hydraulic conductivity of the
matrix is from about 5×10–11 m/s to about 2×10–8 m/s). On the other hand, the matrix porosity (for neglected cavern and fissure porosities) when combined with tracer ages
(or mean travel times) is shown to yield proper values of the hydraulic conductivity (K) by applying the following formula:
K≅(matrix porosity×mean travel distance)/(mean hydraulic gradient×mean tracer age). Confirming earlier findings of the authors,
this equation is shown to be of great practical importance because matrix porosity is easily measured in the laboratory on
rock samples, whereas cavern and fracture porosities usually remain unmeasurable.
Received: 21 February 1997 · Accepted: 13 May 1997 相似文献
4.
选择北京平原区水文地质、环境地质等方面都比较典型的沙子营垃圾堆放场,建立了其水文地质模型。在充分收集资料、分析得出部分计算所需参数后,采用现场弥散实验、勘查取样测试等方法,求得了该含水层的弥散系数等参数;用二维非稳定流溶质运移方程对污染物在此含水层中的迁移扩散规律、速度和污染范围等进行了模拟计算;采用现场钻探、取样测试分析等方法,评价了该含水层的实际污染状况。实验模拟计算和现场调查结果表明:污染物在潜水含水层中的运移规律遵循二维非稳定流场中的溶质运移方程,污染物在潜水含水层中的运移速度约为86.25m/a,迁移扩散主要发生在地下水流向上,侧向扩散宽度极小,是地下水流向上的1/17。 相似文献
5.
Nitrate concentrations in multi-aquifer systems are heavily affected by the presence of wellbores (active or abandoned) that
are screened in several aquifers. The spatial variability of hydraulic conductivity in the confining layers has also an important
impact on the concentrations. A synthetic three-dimensional flow and transport exercise was carried in a multi-aquifer system
consisting of two aquifers separated by an aquitard in which 100 vertical wellbores had been drilled. To model the wellbores
and the flow and transport connection between aquifers that they may induce, we assign a high vertical hydraulic conductivity
and a low effective porosity to the cell blocks including the wells. With these parameters, a solute will travel quickly from
one aquifer to the other without being stored in the well itself. The wellbores will act as preferential pathways, and the
solute will move quickly between aquifers according to the hydrodynamic conditions. Not considering these preferential pathways
could induce erroneous interpretations of the solute distribution in an aquifer. We also noted that when there are vertical
wellbores that connect aquifers in a multi-aquifer system, low conductivity in the aquitard enhances the flow of solute through
the wellbores. Time-varying pumping rates induce important fluctuations in nitrate concentrations; therefore, any estimate
of the water quality of the aquifer will depend on the moment when the data has been recorded. Consequently, concentration
maps obtained by interpolation of point samples are seldom a good indicator of the chemical status of groundwater bodies;
alternatively, we recommend complementing the usual interpolated maps with numerical models to gain a true understanding of
the spatial distribution of the solute concentration. 相似文献
6.
M.J. Reeves 《Engineering Geology》1979,14(4):231-240
Pore water in the Chalk is likely to remain essentially static under the influence of environmental forces with the exception of evapotranspiration. A process of piston displacement of water through networks of microfissures provides a possible mechanism for downward percolation through the unsaturated Chalk.
Maintenance of continuous diffusion equilibrium between fissure and pore water throughout downward migration allows the explanation of the observed rates of movement for thermonuclear tritium in the unsaturated zone. Activation of increasingly large fissures with increasing infiltration rates explains observed rapid water-table response under conditions of sustained high inflow, and is consistent with the behaviour of water quality parameters in the saturated aquifer. Whereas in the unsaturated zone it is suggested that 80 to 90% of total flow passes through microfissures, in the saturated aquifer fluid transport is essentially through macrofissures. Diffusion equilibrium between pore water and fissure water in the saturated zone is not therefore expected.
Individual macrofissures occasionally are enlarged by solution, making it possible for a large proportion of saturated flow to take place through relatively few preferential flow channels. Although the macrofissures, and particularly enlarged macrofissures, are largely responsible for aquifer transmissivity, microfissure storage may often be highly significant in terms of specific yield. 相似文献
7.
探讨了将蒙特卡罗(Monte Carlo)方法应用于多尺度非均质含水层中溶质运移模拟的方法。所研究的含水层由两种具有不同渗透系数统计特征的多孔介质所组成,每一种多孔介质是非均质的,且其渗透系数场符合平稳假设,而整个模拟区的渗透系数是非平稳的。Monte Carlo方法要求参数是平稳的,因此,分别对两种多孔介质产生若干随机渗透系数场后,用两种方法进行组合,并进行溶质运移的模拟计算。通过对计算结果的分析,综合考虑计算精度、计算时间等因素,得出了处理多尺度非均质多孔介质中溶质运移问题的较好方法。 相似文献
8.
9.
Fluid and Solute Transport from a Conduit to the Matrix in a Carbonate Aquifer System 总被引：1，自引：0，他引：1
Within carbonate systems, the working hypothesis suggests that when a conduit is flooded fluid and solute migrate from the
conduit into the matrix. This flux of fluid and solute into the matrix creates a reservoir that can be slowly released once
the flooding recedes. Although hypothesized, these fluxes have never been measured. To quantify the distance that a fluid
and solute would move into a matrix, the fluxes of fluid and solute from a conduit into a matrix were simulated for nine different
carbonate aquifer systems. Two independent numerical approaches were used to simulate (1) fluid flux into the matrix and (2)
solute flux into the matrix during a flooding event. When flooding occurs within the conduit, the volume of water transported
into and stored in the matrix with a high porosity and high hydraulic conductivity (Floridan Aquifer) was less than 0.34 m3 along a 1 m length of conduit, resulting in a penetration depth of 7.2×10−2 m into the matrix. In a low porosity and low hydraulic conductivity matrix (Ozark Plateau), the volume of water transported
into and stored in the matrix was less than 6.85×10−5 m3 along a 1 m length of conduit, resulting in a penetration depth of 2.0×10−4 m into the matrix. Simulated solute flow shows that less than 0.1% of the solute moves in to the matrix. The two approaches
demonstrate that during high flow conditions fluid and solute are forced through the conduits, with very little moving into
the carbonate matrix. Once the fluid and solute enter a conduit and are moving, they will remain in the conduit until they
are discharged at an outlet. Thus, a carbonate matrix does not become a reservoir for solute and fluid during a high-flow
event. 相似文献
10.
Groundwater aquifer vulnerability has been assessed by incorporating the major geological and hydrogeological factors that affect and control the groundwater contamination using GIS-based DRASTIC model along with solute transport modeling. This work demonstrates the potential of GIS to derive a vulnerability map by overlying various spatially referenced digital data layers (i.e., depth to water, net recharge, aquifer media, soil media, topography, the impact of vadose zone and hydraulic conductivity) that portrays cumulative aquifer sensitivity ratings in Kishangarh, Rajasthan. It provides a relative indication of groundwater aquifer vulnerability to contamination. The soil moisture flow and solute transport regimes of the vadose zone associated with specific hydrogeological conditions play a crucial role in pollution risk assessment of the underlying groundwater resources. An effort has been made to map the vulnerability of shallow groundwater to surface pollutants of thestudy area, using soil moisture flow and contaminant transport modeling. The classical advection-dispersion equation coupled with Richard’s equation is numerically simulated at different point locations for assessing the intrinsic vulnerability of the valley. The role of soil type, slope, and the land-use cover is considered for estimating the transient flux at the top boundary from daily precipitation and evapotranspiration data of the study area. The time required by the solute peak to travel from the surface to the groundwater table at the bottom of the soil profile is considered as an indicator of avulnerability index. Results show a high vulnerability in the southern region, whereas low vulnerability is observed in the northeast and northern parts. The results have recognized four aquifer vulnerability zones based on DRASTIC vulnerability index (DVI), which ranged from 45 to 178. It has been deduced that approximately 18, 25, 34, and 23% of the area lies in negligible, low, medium and high vulnerability zones, respectively. The study may assist in decision making related to theplanning of industrial locations and the sustainable water resources development of the selected semi-arid area. 相似文献
11.
An iterative inverse method, the sequential self-calibration method, is developed for mapping spatial distribution of a hydraulic
conductivity field by conditioning on nonreactive tracer breakthrough curves. A streamline-based, semi-analytical simulator
is adopted to simulate solute transport in a heterogeneous aquifer. The simulation is used as the forward modeling step. In
this study, the hydraulic conductivity is assumed to be a deterministic or random variable. Within the framework of the streamline-based
simulator, the efficient semi-analytical method is used to calculate sensitivity coefficients of the solute concentration
with respect to the hydraulic conductivity variation. The calculated sensitivities account for spatial correlations between
the solute concentration and parameters. The performance of the inverse method is assessed by two synthetic tracer tests conducted
in an aquifer with a distinct spatial pattern of heterogeneity. The study results indicate that the developed iterative inverse
method is able to identify and reproduce the large-scale heterogeneity pattern of the aquifer given appropriate observation
wells in these synthetic cases. 相似文献
12.
A conceptual model of hydraulic networks in carbonate rocks, illustrated by examples from Poland 总被引：2，自引：1，他引：1
J. Motyka 《Hydrogeology Journal》1998,6(4):469-482
Hydraulic networks of carbonate rocks usually consist of three types of spaces: pores, fissures, and caverns; sometimes filled
forms also are present. At sufficiently large scales, the spaces are assumed to be homogeneous with arbitrary boundaries and
to be characterized by mean values of parameters. A conceptual model and its schematic presentation demonstrate the importance
of particular parameters for flow and solute transport, and they explain the responses of pumping rates and water levels to
changes in boundary conditions. Three examples characterize some typical networks: (1) chalk in eastern Poland, representing
fissured aquifers with a high storage volume for solutes in stagnant matrix water; (2) Middle Triassic limestones in southern
Poland, representing fissured-cavernous aquifers; however, a large storage volume for solute transport is in mostly stagnant
matrix water; and (3) Triassic dolomites in the same area, representing porous-fissured-cavernous aquifers with a considerable
storage volume in the matrix, which can partly be released (20%), considerably contributing to the total specific yield. For
the last two types of aquifers, the hydraulic conductivity near pumping wells and mine galleries usually quickly increases
in time due to suffosion of filled forms, which leads to a temporal large increase of the inflows.
Received, April 1997 Revised, January 1998, August 1998 Accepted, May 1998 相似文献
13.
Estimation of contaminant transport parameters for a tropical sand in a sand tank model 总被引：1，自引：1，他引：0
O. O. Ojuri Ph.D. S. A. Ola Ph.D. 《International Journal of Environmental Science and Technology》2010,7(2):385-394
This research describes the goals, design and implementation of a quasi natural gradient, laboratory scale, sand tank (aquifer) model experiment. The model was used to study the transport of an inorganic tracer (Chloride) in groundwater, within a tropical aquifer (porous medium) material. Three-dimensional sand tank (1.8 m × 0.3 m × 0.8 m) experiments were conducted to investigate contaminant transport and natural attenuation within the sand tank. In all, 360 samples were collected during 24 sampling sessions, for the three days of the tracer experiments in the Sand Tank. The Owena sand is a poorly graded sand with 88.1 % sand and 11.9 % gravel. Geotechnical properties including; coefficient of uniformity Cu = 2.53, coefficient of gradation Cz = 0.181, hydraulic conductivity K = 5.76 × 10?4 m/s, bulk density p = 1.9 Mg/m3, effective porosity ne = 0.215 and median grain diameter D50 = 0.55 mm, were determined. Other relevant hydraulic and solute transport parameters, such as dispersion coefficients and dispersivities were also established for the tropical soil. 相似文献
14.
15.
局域化改进集合卡尔曼滤波（EnKF）可以克服EnKF方法在使用小集合时,对参数识别精度较低的缺陷,其能同化
地下水位观测数据有效识别渗透系数场。实际工作中,溶质运移数据也较容易获得。崔凯鹏（2013）尝试增加溶质运移
数据以改进只同化水流数据对渗透系数的估计结果,但是精度提高有限。本文在其基础上修改模型,进一步增加溶质注
入井,探究同时同化水头和溶质运移数据,对渗透系数场识别效果,之后对比了局域化EnKF与非局域化EnKF参数识别结
果,并分析了溶质影响范围与参数识别的关系。结果表明：同时同化溶质运移和水头资料,比同化单一种类观测数据识别
的渗透系数精度更高;相同实现数目下,局域化EnKF比EnKF对渗透系数场的估计结果与真实场更为接近;仅考虑溶质影
响范围内的渗透系数,同化水头数据在最后时刻参数识别结果好于同化溶质运移数据参数识别结果,但差别不大。 相似文献
16.
水力传导度是描述孔隙介质物理特性的重要参数,水力传导度的空间变异性直接影响到水分与溶质在介质中的运移状况。由于基于随机理论的方法难于描述具有多重变异尺度的水力传导度的空间变异性,使得基于分形理论的方法得到了较快发展和应用。详细介绍并评述了分形理论和方法的基本特征及研究进展,水力传导度的空间变异分形与弥散尺度效应的关系及其对溶质运移的影响。 相似文献
17.
Samantha Murphy Thomas Ouellon Jean-Marc Ballard Ren�� Lefebvre Ian D. Clark 《Hydrogeology Journal》2011,19(1):195-207
Tritium?Chelium groundwater dating was carried out in a trichloroethylene (TCE)-contaminated valley-fill aquifer system in Quebec, Canada, where a numerical groundwater flow model was developed. Forty seven discrete groundwater and dissolved gas samples were obtained along two flow paths originating from known TCE source zones whose related plumes converge down gradient to form a single plume. Sampling points in monitoring wells were projected onto vertical sections showing particle tracks along the two flow paths. At these points, simulated advective ages obtained from particle tracking were matched to tritium?Chelium ages using different porosity values; the best match was 0.35. Ages were also obtained above and below a prodeltaic silty aquitard in a portion of the aquifer where some source zones are located, which provide groundwater and TCE transit times through the aquitard as well as a mean vertical hydraulic conductivity that agrees with previous estimates used in the model. In certain locations, anomalously old ages associated with high terrigenic 4He indicate areas where groundwater from the underlying proglacial unit flows upward into the deltaic sand aquifer through aquitard windows. Upflow locations correspond with increased TCE concentrations, suggesting significant TCE provenance through the proglacial unit originating from a previously unrecognized TCE source zone. 相似文献
18.
Prediction criteria for groundwater potential zones in Kemuning District,Indonesia using the integration of geoelectrical and physical parameters 
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下载免费PDF全文 The presence of groundwater is strongly related to its geological and geohydrological conditions.It is,however,important to study the groundwater potential in an area before it is utilized to provide clean water.Werner-Schlumberger’s method was used to analyze the groundwater potential while hydraulic properties such as soil porosity and hydraulic conductivity were used to determine the quality and ability of the soil to allow water’s movement in the aquifer.The results show that the aquifer in the Sekara and Kemuning Muda is at a depth of more than 6 meters below the ground level with moderate groundwater potential.It is also found that the aquifer at depths of over 60 m have high groundwater potential.Moreover,soil porosity in Kemuning is found to be average while the ability to conduct water was moderate.This makes it possible for some surface water to seep into the soil while the remaining flows to the rivers and ditches. 相似文献
19.
高阳煤矿主采太原组9-10-11#煤层,矿区内断层、陷落柱发育,奥陶系灰岩溶裂隙水是威胁矿井安全开采的主要水源。据井下突水资料及地面水文地质勘探成果,总结出奥陶系峰峰组岩溶裂隙含水层的赋存特征:①从垂向上看,一段以泥灰岩、石膏、硬石膏为主,为相对隔水层,二段由青灰色及黑色厚层状泥晶、粉晶灰岩组成,钻探可见岩溶裂隙,富水性中等;②从水平方向上看,西部埋藏较浅区富水性明显强于中、东部深埋区,且在向斜轴部出现滞流区;③水位西高东低,相差近300m;④顶部存在隔水层段,隔水层厚度一般3.09~34.01m;⑤水位和水化学特征对比发现,峰峰组与马家沟组含水层没有水力联系;⑥地下水总体自西向东,自北向南径流,侧向径流排出井田外。该研究为煤矿底板水的防治提供了依据。 相似文献
20.
赵勇胜 《吉林大学学报(地球科学版)》1992,(2)
弥散理论是污染质在含水层中运移模型的基本理论.但在实际应用中存在着不少问题和争议.本文对污染质在含水层中运移的弥散作用进行了分析探讨.并应用MOC水质模型对弥散参数的作用进行了分析,证明了在一般情况下,污染质在含水层中的运移主要受对流作用控制,弥散参数的变化对水质模型结果的影响相对较小.在特定的水文地质条件下,弥散作用对污染质的运移是重要的. 相似文献