ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractMost of the water requirement for Madras is met from surface‐ and ground‐water supplies piped in from outside the city limits. However, as is the case for many cities, a certain proportion of the population, usually the poorest, is forced to rely on wells within the urban area. A study was therefore carried out to gain an idea of the inorganic quality of the water in the wells penetrating the shallow (<20 m thick) alluvial aquifer below the city. Two general surveys of selected wells across the city indicated that relative to Indian domestic water standards, of the 93 ground‐water samples obtained, 25% exceeded the Ca limit, 11% the Mg limit, 43% the total dissolved solids limit, 14% the SO4limit, and 70% the NO3limit. As an indicator of biological contamination, the high concentrations of NO3(up to 1040 mg/l) are particularly worrying. A detailed survey of sites close to a city river was also undertaken. High heavy metal concentrations were detected, with As up to 0.42 mg/1, Hg to 0.02 mg/1, Pb to 1.82 mg/1, and Cd and 1.31 mg/1. Microbes have been found in several of the wells. It is clear that, as expected, the shallow ground water is grossly pol

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00821.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractGround water in the plain area of China is recharged mostly with rainfall and to a lesser extent with surface water and nearby ground water. There are several methods for the calculation of recharge of rainfall seepage to ground water. The calculated values using different methods vary due to the accuracy of parameters and calculation methods chosen. A comparative study of methods used to calculate ground‐water recharge by rainfall seepage is made using the water‐balance method and the ground‐water regime analysis method applied to the plain area of China. The accuracy of the ground‐water regime analysis method is superior to that of the water‐balance method. The influential factors (lithology, depth to ground water, precipitation capacity, etc.) of ground‐water recharge by rainfall seepage and the accuracy of these factors are als

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFlow rates and concentrations from fractures intersected by a borehole can be estimated by matching simulated concentration profiles to the observed variations in water chemistry along the borehole. Experiments in karstic rocks prove that hydraulic short circuits between fractures yield a very complex flow pattern, and that flow velocities in the borehole may be higher than the velocity at which the piezometric level varies. Combined temperature and concentration studies characterize flow in both high permeability channels and slightly fissured blocks, as chemical profiles detect low velocity flows that cannot be identified on temperature profiles. Such studies are therefore advisable to characterize natural flow in fractured carbonate rocks, but also in other fractured media.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00823.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe analysis of capture zones of pumping wells is useful for designing pumping systems and wellhead protection programs. Using discharge potentials, equations are derived that can be applied to confined, unconfined, or combined confined and unconfined aquifers. The transient equations are transcendental and cannot be solved explicitly. However, infinite‐time (steady‐state) equations are presented which can be solved. They define an area in which, theoretically, all the water in the aquifer will eventually reach the pumping well, although the equations do not consider the effects of hydrodynamic dispersion. Equations for calculating the stagnation point, upgradient divide, and dividing streamline within the aquifer and an example problem are presen

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00824.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractGround‐water management decisions are usually taken under uncertainty, since they depend on unknown parameters of the aquifer such as hydraulic conductivity and specific discharge. This study applies a number of analytical techniques to a case study in order to demonstrate the potential effect of vertical heterogeneity in the horizontal component of specific discharge on evaluating contaminant travel time in an aquifer. The modified point dilution technique developed by Ronen et al. (1986) is applied to study the vertical variability of the horizontal component of specific discharge in a deep unconfined sandy aquifer. This technique, used under natural flow conditions, employs a multilayer sampler, a tracer, and a mathematical diffusion model. Also analyzed are data from a very large unplanned tracer test where the “tracer”, sewage effluent with a high chloride content, was infiltrated into the aquifer for about 30 years. To date, based on available sedimentological evidence and pumping tests, the aquifer has been regarded as homogeneous. However, information from analysis of the tracer test data by two different flow models, and findings obtained by the modified point dilution technique, indicate the existence of zones of high hydraulic conductivity with specific discharges one order of magnitude higher than expected. As a consequence, chloride breakthrough in a pumping well downstream of effluent infiltration was detected after 10 years, at least 70 years earlier than could have been estimated from previously available data. The results demonstrate that consideration must be given to vertical heterogeneity when evaluating contaminant transport and show that detailed site‐specific field studies are needed in order to prevent or control aquifer contam

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00825.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractGround‐water quantity data were collected at a 22‐acre farm site near Churchtown, Pennsylvania, to determine if terracing changed the quantity of water recharging the aquifer. Double‐mass comparisons of water‐level data from six wells at the site were used to determine that the construction and operation of six pipe‐outlet terraces caused no statistically significant changes in the quantity of recharge to the carbonate aquifer. Analyses of water‐table altitude data from site wells indicate that terracing did not change mean annual water‐table altitude

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00826.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFournier's approximate method for relating self‐potential anomalies to water‐table elevation is satisfactory for five of the six sites where it has been tested in New Hampshire. At these sites water‐table elevations were determined independently from observation of surface‐water bodies and by seismic refraction at the times of the self‐potential surveys.At three sites on drumlins formed of glacial till, the apparent coupling coefficients range from 0.95 to 4 mV/m whereas two surveys on sand and gravel deltas yield apparent coupling coefficients of −16 and −17 mV/m. At a third delta the apparent coupling coefficient suggests that the water table is in an underlying till rather than in the deltaic deposits.Modeling of self‐potential anomalies using Fournier's method may permit isolation of anomalies caused by sources other than ground‐water flow as well as location of significant geological inhomogeneities. Because of nonuniqueness it is not possible to determine water‐table elevations from self‐po

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00827.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractTwo methods for calculating two‐dimensional hydrodynamic dispersion parameters by analyzing experimental data, the dispersive‐plume‐area (DPA) method and the linear‐graphic (LG) method, are proposed in this paper. The DPA method determines the dispersive parameters by analyzing the dispersive plume area after injection of a salt‐water slug into an aquifer. The transverse and longitudinal dispersivity and even the porosity of an aquifer may be derived. The LG method transforms the concentration‐time curve into a straight line. Using the slope of the line, dispersivity and velocity can be obtained. Both methods are examined using theoretical considerations and practic

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA case history is presented for the application of multivariate geostatistical methods to the problem of estimating pesticide concentrations in ground water from measured concentrations of nitrate and pesticide, when pesticide is under‐sampled. The shallow, poorly confined, sand and gravel aquifer underlying the lower Malheur River basin near Ontario, Oregon is contaminated by nitrate and metabolites of the herbicide Dacthal (dimethyl tetrachloroterephthalate) or DCPA. The results of extensive ground‐water sampling indicate that a significant positive correlation exists between measured nitrate and DCPA concentrations in the aquifer. This suggests that future sampling should include a large number of the less‐expensive nitrate analyses, and these data should be used to support the interpretation of fewer, more expensive DCPA analyses. Sample variograms were computed for nitrate and DCPA concentrations and were fit with isotropic, spherical variogram models with correlation ranges of 4 km. Incorporating measured nitrate concentrations in the DCPA estimates obtained by cokriging reduced estimation variances from 14 to 34%. A simple economic analysis demonstrated that for this aquifer, acquiring additional nitrate samples is a cost‐effective way to reduce estimation variances f

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1993.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY