ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02205.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThe Ramapo Fault is a major structural feature of northern New Jersey separating the Triassic‐age Newark Basin from the Precambrian Reading Prong. When the New Jersey Department of Transportation proposed extending Interstate Highway 287 north of Boonton, New Jersey, along the fault alignment, concerns were raised regarding the potential for the fault to act as a preferential source of ground‐water recharge to aquifers supplying domestic and industrial needs. It was feared that highway contaminants and spills could infiltrate the fault zone, be transported along the fault, and recharge the unconsolidated Pleistocene‐age buried valley aquifers, principally the Towaco Valley aquifer.As a result of these concerns, a detailed investigation was performed to determine the location and hydrogeologic character of the fault. Geologic mapping and geophysical techniques were employed to locate the fault prior to core drilling and packer testing of the fault. Geophysical logs were obtained from the borings to assist in characterization of the formation properties and to verify the fault location.The results of the investigation indicate that the Ramapo Fault has a calculated hydraulic conductivity of less than 1 × 10−7cm/sec which was indistinguishable from the surrounding formations. It was concluded that the Ramapo Fault does not provide ground‐water recharge to the unconsolidated buried valley aquifers within the study area. The deltaic deposits overlying bedrock directly up‐gradient of the buried valley exhibited relatively high hydraulic conductivity (10−2cm/sec) providing the major source of recharge to the unconsolidated aquifers in the

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02206.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThis article describes the use of kriging for optimizing data collection and utility in a regional ground‐water investigation of the Potomac‐Raritan‐Magothy aquifer system in central New Jersey. Kriging was used to (1) estimate the altitude of an aquifer surface, (2) estimate hydraulic conductivities from point data, and (3) estimate the associated kriged errors. The selection of locations for additional data collection, based on the kriged errors, was effective in terms of improving the aquifer surface data base. In another application, hydraulic conductivity values were kriged, first using equal weights, then unequal weights to account for the reliability of the data. The weighting values that were used for unequal weighting were estimated by an analysis of variance. Although inclusion of the data reliability in the kriging will increase the kriged errors, the accuracy of the range of uncertainty in the interpolated values also incr

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02207.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTA comparative discussion of several methods for the determination of specific yield is presented. The discussion relies on a pumping test conducted recently by Nwankwor and coworkers from the University of Waterloo in an unconfined aquifer at Borden, Ontario, Canada. We show that a water‐balance method promulgated by these workers and used earlier by others, including Wenzel in 1942 and 1946, is invalid because it overlooks a major component of the water budget. This method suggests erroneously that specific yield increases with time during a pumping test. The method can therefore lead to arbitrarily large specific yield values which may lack physical significance. By relying on this water‐balance method and on laboratory drainage experiments, Nwankwor and coworkers conclude incorrectly that type‐curve methods, such as those proposed by Prickett in 1965 and Neuman in 1975, give unreasonably low specific yield values. We show instead that these specific yield values are consistent with water‐balance considerations when all the components of the water budget are properly taken into account. We further point out that whereas the larger specific yields usually obtained from laboratory drainage experiments may be well suited for the evaluation of ground‐water reserves that can potentially be recovered from an unconfined aquifer over long periods of time, they are not directly relevant to the problem of relating ground‐water level variations to pumpage which is characterized by a shorter time scale. This is especially true when specific yield is taken to be the difference between water content at saturation and residual water content at high suctions as done by Nwankwor and coworkers. The rate at which ground‐water levels drop or fluctuate in response to pumpage is controlled by the smaller specific yield that one obtains from time‐dr

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02208.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTExamples of the use of transient electromagnetic soundings for three ground‐water exploration problems in sedimentary aquifers are given. The examples include: (1) estimating depths to water table and bedrock in an alluvium‐filled basin, (2) mapping a confined fresh‐water aquifer in bedrock sediments, and (3) locating a freshwater/salt‐water interface in a glacial‐outwash aquifer. The technique works quite well for these problems within the limitations imposed by the problem of equivalence. For thin conductive targets (S‐equivalence) such as a salt‐water lens, the ratio of the layer thickness to its resistivity can be determined, but not the individual layer parameters. The thickness of thin resistive zones (H‐equivalence) can be resolved, but the resistivity of such layers is not well determined. The problem of H‐equivalence is more severe than the S‐equivalence. Equivalence imposes restrictions on the transient sounding method for some ground‐water exploration problems. Model studies prior to field work can be used to assess the usefulness of the technique for a particular

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02209.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTIn recent years, several pesticide‐related contaminants have been detected in the ground waters of the State of Hawaii. Two soil fumigants previously used by pineapple growers, 1,2‐dibromo‐3‐chloropropanc (DBCP) and 1,2‐dibromoethane or ethylene dibromide (EDB), have been detected in several wells on Oahu and Maui. An impurity of the soil fumigant DD, 1,2,3‐trichloropropane (TCP), also has been detected in a number of wells. DBCP, EDB, and TCP are of particular concern to State public health officials due to known and possible unknown health effects associated with these compounds.The locations of the contaminated well sites on Oahu appear to be correlated with the areas of past and present pineapple cultivation when the ambient ground‐water flow pattern is taken into consideration. In addition, several large fuel pipeline leaks are located in the vicinity of the EDB contamination. In general, TCP contamination is more widespread than either DBCP or EDB contamination. TCP levels appear to be declining in Oahu water wells while EDB levels in the contaminated portion of southern Oahu appear to be increasing. The direction of temporal trends in DBCP concentration at present varies acco

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02210.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTSeismic reflection surveys were used to follow the drawdown in a shallow aquifer during a pumping test. Using severe analog low‐cut filters and 1/4‐m geophone spacings, 335 Hz reflections were obtained from the top of the saturated zone 2.7 m deep. The reflections moved down in time as the saturated zone dropped in response to pumping. The dominant frequency and bandwidth both dropped during pumping indicating a more diffuse reflecting boundary. Slight pullups of reflectors at specific locations on the CDP sections may indicate a higher elevation of the capillary fringe and therefore finer sediments in those locations. Other potential applications of this technique include mapping cones of depression and detecting and delineating perched‐water t

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02211.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTA method using the nonlinear least‐squares and finite‐difference Newton's method to determine the aquifer parameters via a pumping test in a homogeneous and isotropic confined aquifer system is proposed. The nonlinear least‐squares is used to find the values of transmissivity and storage coefficient such that the sum of the squares of differences between the predicted drawdowns and observed drawdowns is minimized. The finite‐difference Newton's method is used to solve the system of nonlinear least‐squares equations for transmissivity and storage coefficient.Comparisons of the results between the proposed method and graphical methods including the Theis, Cooper‐Jacob, and Chow methods are discussed in detail, showing data of a 6‐hour pumping test.The proposed method has the advantages of high accuracy and quick convergence for most in

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02212.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTA steady‐state hillside seepage problem is solved analytically. Subject to the Dupuit‐Forchheimer assumption, one‐dimensional seepage with uniform recharge over an inclined impervious bed is analyzed. Results are presented graphically showing the profile dependence on a single parameter. Properties of the profiles arc investigated. Profiles are also calculated numerically and plotted to improve the physical interpret

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02213.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTAn unconfined aquifer variation of the Prickett and Lonnquist Aquifer Simulation Model (PLASM) has been modified to simulate the dynamics of seepage face development and compute flow rates therefrom. The modifications, based on hydraulic theory and operating within the framework of the original model, enable the model to simulate zones of seepage contiguous and noncontiguous to streams, lakes, or other points of ground‐water discharge. A simplistic overland flow routing procedure to move seepage flow downslope from points of discharge and permitting it to reenter where the water table is below the land surface was also incorporated.To determine the error associated with this discrete solution, the modified numerical model was compared to a series of analytically equivalent Dupuit‐Forchheimer‐based solutions. The numerical solutions from PLASM compare to the closed‐form solutions to within the uncertainty of the model's finite‐difference discretization. The comparisons indicate that errors in seepage face prediction result strictly from PLASM's inclusion of the D‐F approximations, not from the formulation of the numerical seepage face simulation routine. Finally, the modified PLASM was applied to a hypothetical watershed under dynamic conditions to demonstrate its capabilities.The unconfined aquifer version of PLASM works best in situations where both thickness‐to‐length ratio of the aquifer and land surface and water‐table slopes are relatively small, geometry typical of many real‐world watersheds. Under such conditions, the modifications developed are shown to logically and consistently simulate the extent, dynamics, and flow rates of seepage zones

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02214.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY