bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Movement in Till of East‐Central South Dakota
Authors: Cravens Stuart J. , Ruedisili Lon C. 
Published: March 2006

ABSTRACTResults from the first phase of a study on water movement within the till of east‐central South Dakota indicate that little to no water passes from the weathered till through the underlying unweathered till into underlying outwash deposits. Based on hydrographic analyses, field hydraulic conductivity measurements, and major‐ion sampling at 22 study sites, discharge from the weathered till is hypothesized to be primarily from evapotranspirative losses during periods of high water table. Hydraulic conductivity of the unweathered till is typically 10 to 200 times lower than the weathered till. Water sampled from the unweathered till is up to three times higher in major‐ion concentrations than water in underlying outwash deposits. Carbon‐age dates of water from the buried outwash deposits suggest an age in excess of 9,000 years before the present, corresponding to the Late Wisconsinan glacial epoch.
A Three‐Dimensional Analytical Method for Predicting Leachate Migration
Authors: Huyakorn Peter S. , Ungs Michael J. , Mulkey Lee A. , Sudicky Edward A. 
Published: March 2006

ABSTRACTThis paper presents an analytical model for predicting contaminant transport from a Gaussian vertical strip source in a three‐dimensional uniform ground‐water flow field. The model takes account of hydrodynamic dispersion, adsorption, and decay. In addition, the effects of partial penetration of the contaminant source and finite aquifer thickness are accounted for. Dimensional analysis and type curve procedure are developed for evaluating steady‐state (or maximum attainable) concentration along the plume center line. Application of the type curve procedure is demonstrated. Also included in the presentation is a method for evaluating the effective decay constant of a nonconservative chemical, based on an assumption of simple hydrolysis. The proposed model has been compared with three other analytical models given in the literature. Two simulation examples are presented. Results of the comparison indicate certain advantages of the present model over its previous counterparts.
Biotransformation of Benzene by Denitrification in Aquifer Sand
Authors: Majora David W. , Mayfielda Colin I. , Barkerb James F. 
Published: March 2006

ABSTRACTThis study investigated the biodegradation of benzene, toluene, and the isomers of xylene (BTX) in anaerobic batch microcosms containing shallow aquifer material. BTX loss occurred with the addition of either nitrate or oxygen. Denitrification was confirmed by nitrous oxide accumulation after acetylene blockage of nitrate reductase. When a limiting amount of nitrate was added, there was a corresponding limit to the loss of BTX and a limited amount of nitrous oxide production. We propose that the addition of nitrate to gasoline‐contaminated aquifers would serve as an adjunct to current remedial techniques.
The Combined EMT/VES Geophysical Method for Siting Boreholes
Authors: Beeson Sarah , Jonesa Charles R. C. 
Published: March 2006

ABSTRACTA new simple and quick geophysical method for the siting of boreholes for hand‐pump supply in the crystalline rocks of Kano State, Nigeria has been developed. A single electromagnetic traverse with at least two depths of investigation is used to locate a potential subsurface feature which is then assessed by a vertical electrical sounding. Ground‐water quality has a significant influence on the data. The method and criteria for selecting a site are described in detail because careful site selection is important in reducing the time and money spent on unproductive drilling. In spite of generally unfavorable hydrogeological conditions in the crystalline rocks, 364 boreholes had acceptable rates of ground‐water production out of 429 sited using this method.
Contaminant Plume Analysis Using the Hydrodynamic Dispersion Stream Function (HDSF) Concept
Authors: Batu Vedat 
Published: March 2006

ABSTRACTThe hydrodynamic dispersion stream function (HDSF) concept has been applied to contaminant plume analysis in aquifers. First, the governing equations for the HDSF are summarized both for uniform and nonuniform seepage velocity fields. Application of the methodology is shown with the HDSF developed for a strip contaminant source in a uniform seepage velocity field under steady‐state water flow and solute transport conditions in aquifers. With this solution, it is shown how to determine the hydrodynamic dispersion stream lines (HDSLs) and the hydrodynamic dispersion bounding stream lines (HDBSLs) for a given uniform ground‐water flow field. Applications of the methodology are shown for saturated and unsaturated zones under some idealized conditions. The results of the model may be used for the specification of the boundaries of a contaminant plume and the path lines of contaminant particles under equilibrium conditions.
Saturated and Capillary Fringe Ground‐Water Behavior Near an Excavation
Authors: Mixon F. O. 
Published: March 2006

ABSTRACTIn a hazardous waste disposal facility located in a saturated soil, the local water table and the capillary fringe zone are modified by the presence of the facility. In this paper, a conformal mapping solution to the accompanying ground‐water flow is presented. The solution allows one to display, in the two‐dimensional approximation, the flow net around an excavation in terms of the capillarity, local geometry, and flow properties.Capillarity can significantly influence net flow into an excavation; typical values can cause net flow to be 10 to 20 percent higher than predicted without capillarity.Anisotropic behavior also can be important. It is shown that anisotropy favoring horizontal flow can greatly alter the flow net and the total flow.
An Analytical Solution to Saturated Flow in a Finite Stratified Aquifera
Authors: Yates S. R. 
Published: March 2006

ABSTRACTAn analytical solution for the flow of water in a saturated‐stratified aquitard‐aquifer‐aquitard system of finite length is presented. The analytical solution assumes one‐dimensional horizontal flow in the aquifer and two‐dimensional flow in the aquitards. Several examples are given which describe the use of the analytical solution. The horizontal flow assumption in the aquifer appears to be approximately valid when the hydraulic conductivity of the aquitards is less than or equal to about 10 percent of the aquifer value. A comparison is made between the analytical solution and a saturated‐unsaturated finite‐element solution for a situation where the upper layer is both saturated and unsaturated. For the situation investigated, the comparison indicates that the analytical solution provides an alternative to numerical models even when the upper layer is partially saturated.
A Statistical Evaluation of Formation Disturbance Produced by Well‐Casing Installation Methods
Authors: Morin Roger H. , LeBlanc Denis R. , Teasdale Warren E. 
Published: March 2006

ABSTRACTWater‐resources investigations concerned with contaminant transport through aquifers comprised of very loose, unconsolidated sediments have shown that small‐scale variations in aquifer characteristics can significantly affect solute transport and dispersion. Various sampling and borehole‐logging techniques have been integrated into these studies to detect and measure detailed formation changes through casing or well screen along the length of the borehole. Commonly, measurement accuracy and resolution have been limited by a borehole environment consisting of an annulus of disturbed sediments produced by the casing‐installation method.In an attempt to quantify this disturbance and recognize its impact on the characterization of unconsolidated deposits, three installation methods were examined and compared in a sand‐and‐gravel outwash at a test site on Cape Cod, Massachusetts. These installation methods were: (1) casing installed in a mud‐rotary hole; (2) casing installed in an augered hole; and (3) flush‐joint steel casing hammer‐driven from land surface. Fifteen wells were logged with epithermal neutron and natural gamma tools. Statistical analyses of these digitized nuclear logs proceeded under the fundamental hypothesis that a large variance indicated preservation of layering in the surrounding sediments, significant variability at a small scale, and a small level of disturbance. Conversely, a small variance corresponded to mixing, poor detail, and larger disturbance. The statistical information generated from a systematic “analysis of variance” investigation confirmed an intuitive assessment of the problem by demonstrating that, under the conditions encountered at this site, augering is the most disruptive of the three casing‐installation methods and that driving casing directly, though typically a more time‐consuming operation, transmits the least amount of disturbance into the surrounding formation.
Hydrochemical Characterization of Brines and Identification of Brine Contamination in Aquifersa
Authors: Novak Stephanie A. , Eckstein Yoram 
Published: March 2006

ABSTRACTHydrochemical investigations of aquifer contamination by brine are usually approached using conventional graphical methods (i.e. Stiff, Piper, and Schoeller diagrams). While these methods may be used successfully to identify brine in distinction from other contaminants (e.g., road deicing agents) in ground water, they are unsuccessful in differentiating between brine contaminants from different stratigraphic origins. We present a methodology to be employed in hydrochemical investigations of suspected brine contamination, which incorporates the use of select ionic ratios [Ca:Mg, Na:Ca, Na;Mg, Na:Cl, K:Cl, K:Na, Mg:K, Ca:K, Cl:Mg, Cl:Ca, and (Ca + Mg):(Na + K)] in discriminant analysis and modified graphical methods. The method is tested by applying it to an area of known brine contamination in northeastern Ohio. The results of the test indicate that the method is successful in identifying brine as a contaminant in ground water and in identifying the stratigraphic origin of the brine. This method, when combined with information obtained from drilling reports, can be used to suggest a point source for the brine contamination.
Arsenic in Ground Water of the Western United States
Authors: Welch Alan H. , Lico Michael S. , Hughes Jennifer L. 
Published: March 2006

ABSTRACTNatural occurrences of ground water with moderate (10 to 50 micrograms per liter) to high (greater than 50 micrograms per liter) concentrations of arsenic are common throughout much of the Western United States. High concentrations of arsenic are generally associated with one of four geochemical environments: (1) basin‐fill deposits of alluvial‐lacustrine origin, particularly in semiarid areas, (2) volcanic deposits, (3) geothermal systems, and (4) uranium and gold‐mining areas. These findings are based on an extensive literature review, compilation of unpublished reports and data, and the review of data bases containing more than 7,000 analyses of ground‐water samples for arsenic. In the first two environments, arsenic appears to be associated with sediments derived, in part, from volcanic rocks of intermediate to acidic composition. Dissolved arsenic concentrations in water from volcanic aquifers in the same regions, however, may be low (less than 10 micrograms per liter). Solid phases (minerals, amorphous solids, and sedimentary organic matter) that supply the dissolved arsenic have not been identified in most areas. Alluvial and lacustrine sedimentary deposits appear to be an important source of arsenic in volcanic areas (such as Lane County, Oregon) and in areas underlain by basin‐fill deposits (such as Carson Desert in Nevada and the Tulare Lake basin in California). Mobilization of arsenic in sedimentary aquifers may be, in part, a result of changes in the geochemical environment due to agricultural irrigation. In the deeper subsurface, elevated arsenic concentrations are associated with compaction caused by groundwater withdrawals.
Recharge from a River of Large Width to a Shallow Water‐Table Aquifer
Authors: Mishra G. C. , Seth S. M. 
Published: March 2006

ABSTRACTUsing Zhukovsky's function and Schwarz‐Christoffel conformal mapping technique, unconfined seepage from a river of large width has been analyzed for a steady‐state condition. Seepage quantities occurring through the bed and the bank of the river have been estimated separately. The reach transmissivity constant for a river with large width has been determined. It is found that if the distance between the riverbank and the observation well is more than 0.5 Di, where Di is the saturated thickness of aquifer below the riverbed, the reach transmissivity constant is independent of drawdown at the observation well. The reach transmissivity constant depends on the depth of water in the river and the distance of the observation well from the riverbank.
Artificial Tracer Techniques for the Determination of the Structure of Conduit Aquifers
Authors: Smart C. C. 
Published: March 2006

ABSTRACTFluorescent dye tracer technology now permits accurate determination of tracer breakthrough curves in karst hydrology. Such data may be evaluated in terms of hydraulic processes of dispersion, divergence, convergence, dilution, and storage. The breakthrough curve reflects the character of ground‐water flow and the structure of the ground‐water conduit network, so that within constraints of regional geology, geomorphology, and hydrology, it is possible to interpret tracer breakthrough curves to produce a structural model of a karst aquifer. Such structural models provide a basis for further field investigations and rational computer modeling. An example of such an approach is taken from a series of tracer tests on the Castleguard karst aquifer, Alberta, Canada, an alpine karst with rapid conduit flow, and a strongly seasonal flow regime. A dimensionless recovery index is developed to identify the relationship between springs, and this shows that the behavior and configuration of the active aquifer vary dramatically with discharge.
Simulation of Biodegradation and Sorption Processes in Ground Water
Authors: Srinivasan P. , Mercer James W. 
Published: March 2006

ABSTRACTA one‐dimensional, finite‐difference model for simulating biodegradation and sorption processes in saturated porous media is developed. The model formulation is general and capable of accommodating a variety of boundary conditions and process theories. Advective and dispersive transport of a substrate and an electron acceptor are considered. Aerobic biodegradation is modeled using a modified Monod function; anaerobic biodegradation is modeled using Michaelis‐Menten kinetics. In addition, first‐order degradation is allowed for both substances. Sorption can be incorporated using linear, Freundlich, or Langmuir equilibrium isotherms for either substance. Dirichlet, Neumann, or Cauchy boundary conditions are allowed, where they are constant in time, or include first‐order degradation. The resulting nonlinear problem is solved using a Newton‐Raphson iterative technique. Model verification is achieved through a series of simulations, two of which arc included. In addition, three applications demonstrate the utility of the model.
Effectiveness of Various Aquifer Restoration Schemes Under Variable Hydrogeologic Conditions
Authors: Satkin Richard L. , Bedient Philip B. 
Published: March 2006

ABSTRACTThe USGS MOC Model is a useful tool for evaluating different well patterns in an aquifer restoration scheme under variable hydrogeologic conditions. The best well pattern for a ground‐water cleanup is highly site‐specific and depends upon the objectives and constraints for each problem. In this study, seven different well patterns were investigated to determine the one(s) most efficient in achieving a range of desired levels of contaminant reduction. The well patterns were evaluated on the basis of cleanup time, volume of water circulated, and volume of water requiring treatment. Eight generic hydrogeologic conditions were modeled using different combinations of drawdown, hydraulic gradient, and dispersivity. The key hydrogeologic variables which control the rate of cleanup are well locations, pumping rates, transmissivity, dispersivity, and hydraulic gradient. For a given set of well locations, by varying transmissivity and maintaining drawdown, dispersivity, and hydraulic gradient constant, the cleanup time was found to be inversely related to the pumping rate.
Flow of Ground Water to a Well Near a Stream – Effect of Ambient Ground‐Water Flow Direction
Authors: Newsom Joan M. , Wilson John L. 
Published: March 2006

ABSTRACTAn analytical model has been developed to evaluate and improve our knowledge of steady‐state flow of ground water toward a well near a stream. This model differs from others in that the direction of ambient ground‐water flow (i.e., regional ground‐water flow) does not have to be perpendicular to a gaining stream, but can be oriented in any direction. Without using measured water levels, flow directions and rates can be calculated, i.e. estimated flow nets can be drawn based on the pumping rate, the ambient ground‐water flow rate and direction, and the location of the well and stream. The model can be used to help determine the minimum rate of pumping that will induce infiltration from a stream to a well, and the components of pumping that are derived from the stream and the aquifer. The areal distribution of flow includes: a zone of induced infiltration from a stream toward a pumping well denoted the stream capture zone, a zone that includes all ambient ground water captured by a pumping well called the aquifer capture zone, and a zone downstream of the stream capture zone where water flows from the stream into the aquifer and then back to the gaining stream called the zone of induced throughflow. Each zone could be distinct geo‐chemically. The concepts elucidated by the model are useful for ground‐water pollution studies and for planning purposes. Normalized curves are presented to quickly determine the estimated boundaries between the stream capture zone and the zone of induced throughflow. An example of induced streamflow from Albuquerque, New Mexico illustrates application of the model.
Semianalytical Computation of Path Lines for Finite‐Difference Models
Authors: Pollock David W. 
Published: March 2006

ABSTRACTA semianalytical particle tracking method was developed for use with velocities generated from block centered finite‐difference ground‐water flow models. The method is based on the assumption that each directional velocity component varies linearly within a grid cell in its own coordinate directions. This assumption allows an analytical expression to be obtained describing the flow path within an individual grid cell. Given the initial position of a particle anywhere in a cell, the coordinates of any other point along its path line within the cell, and the time of travel between them, can be computed directly. For steady‐state systems, the exit point for a particle entering a cell at any arbitrary location can be computed in a single step. By following the particle as it moves from cell to cell, this method can be used to trace the path of a particle through any multidimensional flow field generated from a block‐centered finite‐difference flow model.
Determining the Distribution of Hydraulic Conductivity in a Fractured Limestone Aquifer by Simultaneous Injection and Geophysical Logging
Authors: Morin Roger H. , Hess Alfred E. , Paillet Frederick L. 
Published: March 2006

ABSTRACTA field technique for assessing the vertical distribution of hydraulic conductivity in an aquifer was applied to a fractured carbonate formation in southeastern Nevada. The technique combines the simultaneous use of fluid injection and geophysical logging to measure in situ vertical distributions of fluid velocity and hydraulic head down the borehole; these data subsequently are analyzed to arrive at quantitative estimates of hydraulic conductivity across discrete intervals in the aquifer. The diagnostic capabilities of the analysis were found to be constrained by the accuracy and resolution of the logging tools as well as by the hydraulic characteristics of the formation. Despite these limitations, this injection/logging technique appears to be practical and effective under the conditions encountered in this application. The results of this analysis identified the contact margin between the Anchor and Dawn Members of the Monte Cristo Limestone as being the dominant transmissive unit. This section is extensively fractured, and quantitative estimates of its hydraulic conductivity are at least two orders of magnitude larger than that of the surrounding competent rock matrix. This transmissive zone also correlates strongly with an interval where the drilling rate was reported to be quite rapid. Aquifer transmissivity was computed from the profile of hydraulic conductivity and found to be 7.6 × 105 ft2/day, a value that is in close agreement with that determined from a conventional constant‐discharge test. Discrepancies between the two estimates may be scale‐dependent, a function of the different formation volumes investigated by each method. The friction factor, a parameter derived from the differential pressure and velocity logs, appears to be a good indicator of borehole rugosity across intervals where fluid velocity remains virtually unchanged, and vertical flow is turbulent.
Hydrogeology of Clay Till in a Prairie Region of Canada
Authors: Hendry M. J. 
Published: March 2006

ABSTRACTHydrogeologic and isotopic investigations were conducted on thick profiles of clayey glacial till at three study areas in the Interior Plains Region of southern Alberta, Canada. The till consists of an upper weathered zone (9 to 18 m thick) and a lower nonweathered zone (10 to 30 m thick). The presence of tritiated ground water at depths of up to 5 m below the water table in the weathered zones shows that the upper part of the weathered zone is hydrogeologically active. Interpretation of hydraulic head and hydraulic conductivity data, indicates that vertical seepage velocities in the nonweathered till zones range from 2 to 6 m per 1000 years. Calculated lateral ground‐water velocities in the till zones are only about 9 m per 1000 years, and it is concluded that most of the ground water recharging the weathered till zone is returned to the atmosphere by evapotranspiration. Oxygen‐18 and deuterium analyses of ground‐water samples for the weathered till zones support this conclusion.
Simulation and Parameter Identification of Mass Transport in Ground Water
Authors: Häfner F. , Schwan M. 
Published: March 2006

ABSTRACTThe transport of solute components in ground water takes place under the effects of convection, dispersion, and interactions between the stagnant water phase and the solid matrix. The inflow of solutes occurs in the form of local or diffuse sources. Among these, areal sources (precipitation) possess special importance in the recharging of ground water. Today, simulation of the process with multidimensional models is only possible with numerical methods. Since convective transport predominates in many cases, a one‐dimensional simulation scheme along the flow path is proposed for steady‐state ground‐water flow, which is suited to personal computers. This scheme represents the basis for the identification of migration parameters (inverse mass transport problem).