bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation, Identification, and Growth of Well‐Water Bacteria
Authors: Stetzenbach Linda D. , Kelley Lee M. , Sinclair Norval A. 
Published: March 2006

ABSTRACTGround water from deep wells was sampled for the presence of heterotrophic bacteria. Over 500 bacteria were isolated from well‐water samples on a low‐nutrient medium (R2A). Gram‐negative, rod‐shaped, nonmotile bacteria predominated, and Acinetobacter spp. comprised 54% of the total number of isolates. Selected isolates were inoculated into unamended and carbon‐enriched well water, and growth was measured by acridine orange direct count (AODC). Carbon sources included glucose, acetate, pyruvate, and succinate in 100 μg carbon/liter and 1,000 μg carbon/liter concentrations. The isolates grew in unamended filtered well water within 24 hours, and growth of an Acinetobacter sp. was further stimulated (greater than two orders of magnitude within five days) in the carbon‐enriched well water.
Inverse Problem in Ground Water: Model Application
Authors: Khan Irfan A. 
Published: March 2006

ABSTRACTThe inverse model developed in the companion paper entitled, “Inverse Problem in Ground Water: Model Development,” has been applied to the Fairfax‐New Baltimore aquifer in the lower Great Miami River Valley, Ohio. The information obtained from U.S. Geological Survey maps showed four distinct zones of differing hydraulic conductivities in the aquifer. The initial guesses for the hydraulic conductivities were made subjectively. The values of storativity were also assigned subjectively. The inverse model converged within five iterations, and an excellent match with the historical data was obtained. A sensitivity analysis was made to determine the response of the model to various initial guesses for the hydraulic conductivity, various assigned values of storativity, and the number of zones. The sensitivity analysis showed that the calculated hydraulic conductivities were insensitive to initial guesses but sensitive to the assigned values of storativity and the number of zones. However, reasonable deviations in the assigned values were absorbed by the surrogate hydraulic conductivity and the model remained a good input‐output model.
Use of a Numerical Ground‐Water Flow Model for Hypothesis Testing
Authors: Krabbenhoft David P. , Anderson Mary P. 
Published: March 2006

ABSTRACTField studies along the southeastern shore of Trout Lake, Wisconsin, documented the presence of downward hydraulic gradients in a known discharge area as well as an anomalous distribution of seepage to the lakebed which deviates significantly from the generally accepted dogma that ground‐water seepage rates decrease exponentially with distance from shore. A numerical ground‐water model facilitated identification of the hydrologic control, namely the presence of a unit of high hydraulic conductivity, that accounts for the anomalous data, and is important for understanding the dynamics of the flow system. Field data including seepage measurements, visual inspection of lakebed materials and springs, and information obtained during drilling, indicate that a lens of coarse‐grained material intersects the lake. However, the significance of the coarsegrained material was not fully appreciated until a ground‐water model was used to simulate the flow system. The model indicated that the presence of the coarse‐grained lens has a marked effect on the flow pattern in the nearshore area causing downward hydraulic gradients which divert ground water into the lens and cause the occurrence of a localized high‐seepage area offshore where the lens intersects the lake. The numerical model predicts the anomalous seepage distribution noted in the field and the downward hydraulic gradients demonstrating that numerical models are practical tools for interpreting field data and for use in hypothesis testing.
Parameter Identification of a Ground‐Water Contaminant Transport Model
Authors: Strecker Eric W. , Chu Wen‐sen 
Published: March 2006

ABSTRACTA parameter identification (PI) procedure is developed and implemented with the United States Geological Survey's Method of Characteristics (USGS‐MOC) model. The PI procedure can be used to estimate selected model parameters from limited observations by quadratic programming. The code combining the PI procedure and the USGS‐MOC model has been tested by two numerical examples from a hypothetical aquifer. The test results show that the proposed algorithm can identify transmissivity and dispersivity accurately under ideal situations. The effects of using a simple characterization of the aquifer on parameter estimation and model are shown. Because of the improved efficiency in model calibration, extended application to field conditions is encouraged. However, it is cautioned that the interested users should be aware of the difficulties in field applications of PI, and it is recommended that sound engineering and scientific judgements are always needed in the use of the proposed, or any other PI method.
A Simplified Analysis of Two‐Well Tracer Tests in Stratified Aquifers
Authors: Güven O. , Falta R. W. , Molz F. J. , Melville J. G. 
Published: March 2006

ABSTRACTThis paper illustrates several interesting effects of aquifer stratification on the results of two‐well tracer tests by means of a simplified computer model. In the model, it is assumed that the aquifer is horizontal, confined, of constant thickness and porosity, and perfectly stratified in the vicinity of the test wells. The nonuniform advection pattern is taken into account in detail by the model, but the local hydrodynamic dispersion is completely neglected. This simplified model has been verified in part by comparisons with available analytical solutions valid for homogeneous aquifers and in part by comparisons with the results of a two‐well field experiment of Pickens and Grisak (1981a) which was performed in a locally stratified aquifer. The applications of the model to several field situations with assumed values of the relevant parameters show that the concentration versus time breakthrough curve measured at the withdrawal well during a standard two‐well test would be very sensitive to variations of the hydraulic conductivity in the vertical. Without the use of supplementary observation wells with isolated multilevel sampling points, the standard test would give little useful information about the hydraulic and dispersive characteristics of an aquifer. Factors such as the length of the tracer injection period, the use of recirculation and the physical size of the experiment all have a strong effect on the breakthrough curve measured at the withdrawal well, making the interpretation of field results difficult unless aquifer stratification is measured and properly taken into account.
Geochemistry of Salt Water Beneath the Rolling Plains, North‐Central Texasa
Authors: Richter Bernd C. , Kreitler Charles W. 
Published: March 2006

ABSTRACTSodium‐chloride brine underlies the shallow subsurface and discharges at numerous surface locations in the Rolling Plains of north‐central Texas. According to the ratios of Na/Cl and Br/Cl, and supported by the contribution of other chemical constituents, two major brine types can be distinguished: (1) brine derived from dissolution of halite by fresh ground water, and (2) brine derived from discharge of deep‐basin brine aquifers. All salt‐spring brines as well as shallow subsurface brines in the northern and western parts of the Rolling Plains represent halite‐dissolution brine, whereas deep‐basin brine is represented by samples in the shallow subsurface in the south.The oxygen and hydrogen isotopic composition of the halite‐dissolution brines indicates a local, meteoric origin for these brines. Shallow subsurface samples from the southeastern Rolling Plains graphically include deep‐basin brine values and meteoric‐water values as end points, suggesting mixing of deep‐basin brine with local meteoric ground water.
Interpretation of Slug Test Data
Authors: Pandit Nitin S. , Miner Robert F. 
Published: March 2006

ABSTRACTSlug tests offer a quick and inexpensive field method of obtaining localized permeability values. The most commonly used method of interpreting slug test data by Black (1978) requires considerable engineering judgement, and can potentially lead to inconsistency in its application. One of the inconsistencies is usually in the estimation of the initial excess head; the proposed Translation Method offers a way of reducing the inconsistency. Another inconsistency can result from the subjective process of matching actual data with published type curves of expected well response in different aquifers. It is proposed that a standard numerical method should be employed for consistent application and automation of this process. The development of these procedures has led to the implementation of an interactive software package that allows the consistent application of slug test analysis at a lower cost.
Preliminary Evaluation of a Geothermal Aquifer in Southern England
Authors: Burgess W. G. 
Published: March 2006

ABSTRACTThe preliminary evaluation of the first direct‐use (low enthalpy) geothermal well in the United Kingdom included core analysis, geophysical logging, and drill‐stem testing. The effective aquifer is restricted to a few relatively thin loosely cemented bands in the Triassic sandstones at a depth of approximately 1660 m. With an aquifer temperature of at least 67°C the initial assessment of transmissivity, 18 m2/day, suggested that a thermal yield of approximately 2.5 MW would be obtainable. The results are in reasonable agreement with those of a subsequent long‐term production test.
Gaseous Behavior of TCE Overlying a Contaminated Aquifer
Authors: Marrin Donn L. , Thompson Glenn M. 
Published: March 2006

ABSTRACTShallow soil gas (<2 meters deep) was collected and analyzed for trichloroethylene (TCE) to determine the relationship with ground‐water contamination directly below. The gaseous TCE plume was mapped with 46 probes and spanned three orders of magnitude in concentration (<0.001 to 2 μg/1). TCE concentrations in water from five monitoring wells around the study site ranged from 4 to 2800 ppb and had a correlation coefficient (r) of 0.90 with TCE concentrations in shallow soil gas. Vertical borings were completed to the water table at four locations in order to obtain profiles of soil gas contamination, air porosity, and water saturation. Gaseous diffusion and air/water partitioning are probably the dominant mechanisms involved in transporting TCE from the ground water to the shallow soil gas.
Characterization of Fracture Permeability with High‐Resolution Vertical Flow Measurements During Borehole Pumping
Authors: Paillet F. L. , Hess A. E. , Cheng C. H. , Hardin E. 
Published: March 2006

ABSTRACTThe distribution of fracture permeability in granitic rocks was investigated by measuring the distribution of vertical flow in boreholes during periods of steady pumping. Pumping tests were conducted at two sites chosen to provide examples of moderately fractured rocks near Mirror Lake, New Hampshire and intensely fractured rocks near Oracle, Arizona. A sensitive heat‐pulse flowmeter was used for accurate measurements of vertical flow as low as 0.2 liter per minute. Although boreholes were spaced at intervals ranging from 10 to 50 meters, acoustic televiewer logs showed little direct continuity of individual fractures from borehole to borehole in either the moderately fractured rocks or intensely fractured rocks. Results indicated that nearly all inflow and outflow to boreholes occurred by means of one or two discrete fractures in both cases. These fractures did not appear very different from other prominent fractures indicated on televiewer and resistivity logs for these boreholes. Hydraulic connections between boreholes apparently were composed of conduits formed by the most permeable portions of intersecting fractures. Most flow in the moderately fractured rocks occurred at isolated fractures at a depth of about 45 meters indicating a nearly horizontal zone of fracture permeability composed of orthogonal, steeply dipping fractures. Previous studies have identified a zone of horizontal permeability in the lower part of the boreholes in the intensely fractured rocks, but flowmeter tests indicated that flow also entered and exited individual boreholes by means of one or two steeply dipping fractures. These results indicate zones of fracture permeability in crystalline rocks are composed of irregular conduits that cannot be approximated by planar fractures of uniform aperture, and that the orientation of permeability zones may be unrelated to the orientation of individual fractures within those zones.
Reverse Pathline Calculation of Time‐Related Capture Zones in Nonuniform Flow
Authors: Shafer John M. 
Published: March 2006

ABSTRACTA simple to understand and easy to implement numerical technique, based on reverse calculation of ground ‐water flow paths, is applied to delineation of time‐related capture zones around water‐supply wells. The areal extent of a t‐year capture zone in a two‐dimensional regional flow domain is approximated by a large set of reverse pathlines all with t‐year travel times. The numerical approach is suitable for calculation of time‐related capture zones in steady, nonuniform flow with inhomogeneous, anisotropic aquifer conditions. The example applications show the sensitivity of this technique to the influence of multiple wells in a block inhomogeneous flow regime.
Diffusivity of Glacial‐Outwash Aquifer by the Floodwave‐Response Technique
Authors: Reynolds Richard J. 
Published: March 2006

ABSTRACTAquifer diffusivity (transmissivity divided by storage coefficient) was calculated for three sites in a glacial‐autwash valley aquifer near Cortland, New York from water‐level fluctuations induced by rises in stream stage. The observed response data were analyzed through use of a one‐dimensional floodwave‐response model to calculate the theoretical head response in the aquifer generated by a floodwave in the stream, and then matched to the observed head response. Diffusivity values computed from sharply peaked flood rises ranged from 6.08 to 8.68 ft2. The closest match between observed and calculated heads was obtained from a site where the aquifer is confined and the saturated thickness (and thus the diffusivity) remains constant with the passage of a floodwave. Arrival time of the observed flood‐peak seems to be the most useful criterion for curve matching, especially under unconfined conditions, where a match to the rising limb and floodpeak is difficult because of changes in the saturated thickness.A transmissivity value of 14,700 ft2/d for the glacial‐outwash aquifer, calculated from specific capacity data from a nearby industrial well, combined with diffusivity calculated by the floodwave‐response method, indicates a storage coefficient between the normal ranges for unconfined and confined aquifers. Calculated storage coefficients were 0.015, 0.027, and 0.034 at the three sites.The floodwave‐response method of calculating aquifer diffusivity is relatively inexpensive compared to standard aquifer tests and is effective in glacial‐valley fill aquifers that are hydraulically connected to a major stream or river.
Monitoring Well Installation, Purging, and Sampling Techniques ‐ Part 1: Conceptualizations
Authors: Keely Joseph F. , Boateng Kwasi 
Published: March 2006

ABSTRACTCommonly employed techniques for the installation, purging, and sampling of monitoring wells are examined. The degree to which hollow‐stem augering disturbs the near‐borehole environment, and how this may result in the movement of contaminated solids or fluids from one stratum to another is discussed. The desirability of driving temporary casing to shield one stratum from another, and to improve the general quality of the monitoring well installation (especially the effectiveness of the filter pack emplaced), is argued. A call for further testing of sampling devices, based on limited field comparisons and a lack of reports of conclusive tests elsewhere, is given.
A Comparison of Field and Laboratory Methods for Determining Contaminant Flow Parameters
Authors: Taylor S. R. , Moltyaner G. L. , Howard K.W.F. , Killey R.W.D. 
Published: March 2006

ABSTRACT In situ estimates of advective and dispersive properties of ground‐water flow systems are essential for the adequate prediction of solute flow. Field tracer tests provide the best estimates of these properties; however, this approach is often precluded by the expense and time involved. Various laboratory techniques have been developed to circumvent these problems and provide convenient estimates of hydraulic conductivity and dispersivity. Although these techniques are used extensively in hydrogeological investigations, very few attempts have been made to compare their estimates with field values.A detailed investigation was performed on an unconfined sand aquifer using a combination of routine laboratory techniques and an innovative field tracer test. The extensive data set provided a unique opportunity to compare field results with those obtained by a variety of laboratory techniques.The hydraulic conductivity results from two different methods of grain‐size analysis (Hazen, 1893; and Masch and Denny, 1966) were observed to be quite well correlated, although their absolute values did not correspond with the hydraulic conductivities determined from the tracer test. However, contrary to previous studies, the results from grain‐size analysis were the same order of magnitude as the in situ values. In addition, the two grain‐size methods appear to provide upper and lower boundaries within which lie the hydraulic conductivity estimates determined from the tracer test. Thus, grain‐size analysis of moderately to well sorted sands may provide reasonable and convenient approximations of hydraulic conductivities of the aquifer.No correlation was observed between field tracer test longitudinal dispersivity values and those determined from laboratory column tracer tests. The latter, however, differed by only an order of magnitude from the in situ point measurements, a difference which is considerably smaller than has been previously reported. This is largely attributed to the accuracy of the sampling methods used in the tracer tests.
PERFORMANCE AND ANALYSIS OF AQUIFER TRACER TESTS WITH IMPLICATIONS FOR CONTAMINANT TRANSPORT MODELING–A PROJECT SUMMARY
Authors: Molz Fred J. , Güven Oktay , Melville Joel G. , Keely Joseph F. 
Published: March 2006

ABSTRACTThe scale‐dependence of dispersivity values used in contaminant transport models to estimate the spreading of contaminant plumes by hydrodynamic dispersion processes was investigated and found to be an artifact of conventional modeling approaches (especially, vertically averaged parameters in two‐dimensional plume simulations). The work reported here shows that variations in hydraulic conductivity with depth result in significant variations in ground‐water flow and contaminant transport velocities; it is the resulting velocity variations that, if vertically averaged, give rise to apparent scale‐dependency of dispersion (e.g., increased dispersion with increasing travel distance). Special depth‐selective observation well designs are recommended by the authors for use in tracer tests, so that detailed estimates of the variations in hydraulic conductivity, and flow and transport velocities can be obtained. Innovative modeling techniques that take advantage of the detailed information obtainable from such tests (by emphasizing advective transport, as opposed to dispersive transport), have been developed by the authors. These modeling techniques are shown to have an element of true predictive ability, being able to closely simulate actual results with little or no calibration.
Effect of Water‐Level Recoveries on Fault Creep, Houston, Texas
Authors: Holzer Thomas L. , Gabrysch Robert K. 
Published: March 2006

ABSTRACTFault creep has stopped or slowed in the eastern part of the Houston, Texas, land subsidence area where reductions in pumping of ground water have allowed water levels to recover partially. Creep has continued across faults in the western part where heavy pumping causes water levels to continue to decline. The observations support the long‐suspected relation between historical faulting and withdrawal of ground water and indicate that partial water‐level recoveries can reduce fault movement and structural damage.
Beneficial Aspects of Sea‐Water Intrusion
Authors: Howard Ken W. F. 
Published: March 2006

ABSTRACTThe Permo‐Triassic sandstone aquifer of northwest England has been a major source of ground‐water supply since the early 19th century. Between Liverpool and Manchester, ground‐water resource development has led to a considerable lowering of the water level inland and intrusion of sea water from the Mersey Estuary and Manchester Ship Canal. As part of a detailed investigation of resource management, a two‐dimensional finite‐difference flow model was developed to represent aquifer behavior for the period 1840 to 1980. Subsequently, this model was used to predict the effects of implementing various management strategies over a 40‐year period ending 2020.Results indicate that ground‐water withdrawals have exceeded natural replenishment by an average of 100% during the past 50 years. In this time the potentiometric heads have responded remarkably slowly to the flow imbalance, a resilience that is largely attributed to the inflow of sea water at rates only marginally less than recharge from meteoric sources. Careful development of the fresh ground‐water resources has minimized water quality problems along the estuary and ship canal, and the model clearly shows how controlled inflow of saline water can considerably enhance the recovery of fresh ground‐water reserves. Difficulties arise only when excessive exploitation accelerates water quality deterioration. Model calculations indicate that inflow of saline water would continue for over 10 years following complete cessation of fresh ground‐water production.
Large Data Bases and Regional Ground‐Water Quality Assessments ‐ An Iowa Case Study
Authors: Rajagopal R. 
Published: March 2006

ABSTRACTMany state and federal agencies routinely collect ground‐water quality data to meet a variety of objectives. The WATSTORE (Water Data Storage and Retrieval System) data files of the U.S. Geological Survey containing raw ground‐water quality data from 4,388 wells and the MSIS (Model State Information System) data files of the U.S. EPA containing finished (blended and/or treated) ground‐water quality data from 2,137 public water‐supply sources are the only two large computer‐coded data files on Iowa ground‐water quality. These two data bases, by themselves, provide significant insights regarding the distribution of chemicals in different hydrogeological environments and the compliance status of PWS sources with reference to drinking‐water quality standards in Iowa. With minor modifications, these two data bases can be integrated to: (a) provide statistical, spatial, temporal, and geological summaries of observed ground‐water quality; (b) determine the extent of exposed populations to various contaminants in their different concentrations; (c) provide necessary information to reduce the existing list of contaminants and include some of those that are not being monitored now; (d) identify gaps in current data‐gathering efforts and prioritize the various components of future monitoring programs; (e) identify potential linkages for the combined use of ground‐water quantity and quality, socioeconomic, land‐use, and public health data; and (f) alert policy makers to potential ground‐water quality problems facing the state. Some of the limitations of the two data bases and the need for integrating them is demonstrated by a comparative analysis and evaluation.