bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Determination of Subsurface Microbial Enzyme Kinetics
Authors: Istok J.D. , Field J.A. , Schroth M.H. 
Published: December 2005

AbstractThe single‐well, push‐pull test has been used in previous field studies to measure in situ zero‐ and first‐order rates for aerobic and anaerobic microbial respiration in the saturated zone. In this paper we demonstrate that the test can also be used to obtain more generalized descriptions of the kinetics of microbially mediated enzymatic reactions. Laboratory and field tests were performed with the model enzyme substrate p‐nitrophenyl‐β‐D‐glucopyranoside (PNG). During a push‐pull test, injected PNG is hydrolyzed in situ to p‐nitrophenol (PNP); the rate of PNP production is taken as a measure of the β‐glucosidase activity expressed by indigenous microorganisms. Laboratory tests were performed in physical aquifer models packed with natural aquifer sediment; field tests were performed in a shallow unconfined alluvial aquifer at a petroleum contaminated site. The laboratory and field tests demonstrate that it is possible to compute the in situ rate of PNP production as a function of PNG concentration using only data from a single push‐pull test. These data can then be used to estimate the Michaelis‐Menton kinetic parameters Vmax and Km for the hydrolysis reaction. This approach potentially extends the range of applicability of the push‐pull test approach for use in determining kinetic parameters for a wide range of microbial processes in situ. These could include the broad class of substituted nitrophenyl substrates used to assay other enzyme systems, as well as microbially mediated redox reactions that occur during contaminant transformations.
A Variable‐Volume, Head‐Dependent Mine Water Filling Model
Authors: Banks David 
Published: December 2005

AbstractCurrent simple mine water filling models suffer from two drawbacks: (1) they often do not account for variations in mine void volume with depth; and (2) they assume that recharge to the mine is approximately constant. The Mine Water Filling Model (MIFIM) presented here rectifies these drawbacks by presenting the concept of effective area (Ea) in a lookup table and assigning deep ground water inflows a conductance whereby inflow varies in inverse proportion to mine water head, once the mine water level exceeds the level of the water inflow. The MIFIM concept may be readily programmed in a computer spreadsheet environment, with simple graphical output. The approach is particularly suited to mines in low permeability rock, with a limited number of discrete inflow features.
Analytical Procedure for Simultaneous Use of Seven Fluorobenzoates in Multitracer Tests
Authors: Dalian Ofer , Ronen Zeev 
Published: December 2005

AbstractAn analytical procedure allowing simultaneous use of seven fluorobenzoate (FBA) isomers was developed and examined through column and field tracer experiments. The analytical method, based on high performance liquid chromatography (HPLC), included a reverse‐phase separation method. This method was found to be very efficient for the FBA analysis, allowing accurate determination of seven FBAs in a single HPLC run, while avoiding analytical interference of other natural water constituents or pollutants. Consequently, this separation method allows the simultaneous use of seven isomers in multitracer tests in highly saline or contaminated environments. The mobility properties of the FBAs were examined in percolation experiments through a column filled with a mixture of crushed chalk and common fracture filling and coating material. The FBAs behaved conservatively as compared to bromid. All seven FBA isomers were successfully used in a multitracer test in a field percolation experiment designed to identify flowpath along a fracture plane.
Comparison of Upscaling Methods to Estimate Hydraulic Conductivity
Authors: Vidstrand Patrik 
Published: December 2005

AbstractA hydraulic field test program was performed at a hard rock laboratory (Aspo HRL) on the Swedish east coast to test upscaling theories. The test program investigated the rock volume around a borehole located at a depth of approximately 340 m below sea level. Hydraulic packer tests were performed at various scales, from 2 m to the entire borehole length of 296 m. From this set of data the predictive ability of different upscaling methods could be evaluated.The comparison of the evaluated “true” field scale hydraulic conductivity with the upscaled hydraulic conductivity yielded that the majority of the upscaling methods tested in this paper predict the large scale values with significant accuracy. However, the ability to predict rapidly decreases when the variance of the natural logarithm of hydraulic conductivity of the subsamples is larger than one. Such a variance is consistently found in the crystalline rocks at the tested site at the 2 m scale. However, at scales of 10 m and larger, a variance larger than one is uncommon. Therefore, it is concluded that there exists a smallest possible scale for use of hydraulic pumping test results for estimating the effective hydraulic conductivity at scales typical for regional flow.
A First Estimate of Ground Water Ages for the Deep Aquifer of the Kathmandu Basin, Nepal, Using the Radioisotope Chlorine‐36
Authors: Cresswell Richard G. , Bauld John , Jacobson Gerry , Khadka Mohan Singh , Jha Mani Gopal , Shrestha Minesh Prasad , Regmi Sushila 
Published: December 2005

AbstractThe Kathmandu Basin in Nepal contains up to 550 m of Pliocene‐Quaternary fluvio‐lacustrine sediments which have formed a dual aquifer system. The unconfined sand and gravel aquifer is separated by a clay aquitard, up to 200 m thick, from the deeper, confined aquifer, comprised of Pliocene sand and gravel beds, intercalated with clay, peat, and lignite. The confined aquifer currently provides an important water supply to the central urban area but there are increasing concerns about its sus‐tainability due to overexploitation.A limited number of determinations of the radioisotope 36Cl have been made on bore waters in the basin, allowing us to postulate on the age of ground water in the deeper, confined aquifer. Ground water evolution scenarios based on radioisotope decay, gradual dissolution of formational salts as the ground waters move downgradient, and flow velocity estimations produce comparable ground water ages for the deep waters, ranging from 200,000 to 400,000 years. From these ages, we deduce a mean ground water flow velocity of only 45 mm/year from recharge in the northeast to the main extraction region 15 km to the southwest. We thus estimate current recharge at about 5 to 15 mm/year, contributing 40,000 to 1.2 million m3/year to the ground water system. Current ground water extraction is estimated to be 20 times this amount. The low specific discharge confirms that the resource is being mined, and, based on current projections, reserves will be used up within 100 years.
Hydrogeological Research: Beginning of the End or End of the Beginning?
Authors: Schwartz Franklin W. , Ibaraki Motomu 
Published: December 2005

AbstractThis paper uses citation data to assess whether articles published in key ground water journals such as Ground Water (GW) and Water Resources Research (WRR) are impacting research. Citation information was obtained from SCI Journal Citation Reports and The Web of Science—databases maintained by the Institute for Scientific Information (ISI). Information extracted from The Web of Science was processed further to remove corrections to papers, discussion/replies, and book reviews. Generally, there are many ground water papers published, but citations of these papers are limited. Approximately 10% to 15% of WRR articles, and 2% to 3% of GW articles attract more than 50 citations in their lifetimes. In both GW and WRR, the top 10% of papers eventually will contribute nearly half of the total yearly citations. Another emerging trend is a diminishing emphasis on citations to new work as compared to work more than 10 years in age. When articles in Ground Water or Journal of Hydrology cite papers in Water Resources Research, those papers cite work 10 or more years old half of the time. If one believes that citations are a measure of science impact, then there is cause for concern. Research is inefficient with much produced for little gain. On a typical industrial life‐cycle curve, ground water research is likely ranked as mature and close to aging. At this stage, much work will have been completed and the number of truly impactful problems will have dwindled to just a few.
Riverbed Permeabilities: Information from Pooled Data
Authors: Calver Ann 
Published: December 2005

AbstractNumerical values of hydraulic conductivities of river channel‐lining materials are assembled from published and unpublished sources. These are found to cover a range from below 1.0×10−9 to above 1.0×10−2 m sec1 and to be concentrated in the region 1.0×10−7 to 1.0 ×10−3 m sec−1. Variability within a site can be large. Assessment of the values in relation to sediment, scale, and method of determination presents a complex picture, and generalization is not straightforward. Hydraulic conductivity determinations from numerical modeling, which tends to be associated with averaging at larger spatial scales, are associated with a more conservative range of values than those derived from field and laboratory analyses. The sample of determinations provides a guideline basis of representative values for hydrological and hydrogeological assessment where specific investigation is not possible.
A Numerical Model and Spreadsheet Interface for Pumping Test Analysis
Authors: Johnson Gary S. , Cosgrove Donna M. , Frederick David B. 
Published: December 2005

AbstractCurve‐matching techniques have been the standard method of aquifer test analysis for several decades. A variety of techniques provide the capability of evaluating test data from confined, unconfined, leaky aquitard, and other conditions. Each technique, however, is accompanied by a set of assumptions, and evaluation of a combination of conditions can be complicated or impossible due to intractable mathematics or nonuniqueness of the solution.Numerical modeling of pumping tests provides two major advantages: (1) the user can choose which properties to calibrate and what assumptions to make; and (2) in the calibration process the user is gaining insights into the conceptual model of the flow system and uncertainties in the analysis. Routine numerical modeling of pumping tests is now practical due to computer hardware and software advances of the last decade.The RADFLOW model and spreadsheet interface presented in this paper is an easy‐to‐use numerical model for estimation of aquifer properties from pumping test data. Layered conceptual models and their properties are evaluated in a trial‐and‐error estimation procedure. The RADFLOW model can treat most combinations of confined, unconfined, leaky aquitard, partial penetration, and borehole storage conditions. RADFLOW is especially useful in stratified aquifer systems with no identifiable lateral boundaries. It has been verified to several analytical solutions and has been applied in the Snake River Plain Aquifer to develop and test conceptual models and provide estimates of aquifer properties. Because the model assumes axially symmetrical flow, it is limited to representing multiple aquifer layers that are laterally continuous.
Application of Continuous Time Random Walk Theory to Tracer Test Measurements in Fractured and Heterogeneous Porous Media
Authors: Berkowitz Brian , Kosakowski Georg , Margolin Gennady , Scher Harvey 
Published: December 2005

AbstractWe examine a set of analytical solutions based on the continuous time random walk (CTRW) approach, which can be evaluated numerically and used to analyze breakthrough data from tracer tests. Practical application of these solutions, with discussion of the physical meaning of the relevant model parameters, is emphasized. The CTRW theory accounts for the often observed non‐Fickian (or scale‐dependent) dispersion behavior that cannot be properly quantified by using the advection‐dispersion equation. The solutions given here, valid for a wide range of dispersive behaviors of conservative tracers, and useful for both characterization and prediction, have been integrated into a library of external functions for use with the GRACE graphical display and analysis package. Example applications of these solutions are presented. The library and graphics software are freely accessible from a Web site.
Comparison of Continuous and Cyclic Pumping from a Well
Authors: Kawecki M. Wojciech 
Published: December 2005

AbstractTwo practically applicable pumping patterns for wells are: (1) continuous pumping at a sustainable constant rate; and (2) pumping at a sustainable constant rate for a fixed period every day (cyclic pumping). Theoretical analysis shows that with the cyclic pumping pattern the pump can be run at a higher rate than with continuous pumping. However continuous pumping at the maximum continuously sustainable constant rate produces considerably more water. If the objective is to produce as much water as possible, it is important to use a pump designed for running at the maximum continuously sustainable rate.
Turbulent Flow Through Porous Media
Authors: Barr Douglas W. 
Published: December 2005

AbstractThe pressure driving flow through porous media must be equal to the viscous resistance plus the inertial resistance. Formulas are developed for both the viscous resistance and the inertial resistance. The expression for the coefficient of permeability consists of parameters which describe the characteristics of the porous medium and the permeating fluid and which, for unconsolidated isotropic granular media, are all measurable. A procedure is proposed for testing for the occurrence of turbulence and calculating the effective permeability when it occurs. The formulas are applied to a set of data from 588 permeameter runs ranging from laminar to highly turbulent. The equations fit the data from the permeameter closely through the laminar flow conditions and quite closely through the turbulent conditions. In the turbulent range, the plotting of the data separates into three distinct lines for each of the three shapes of particles used in the tests. For the porous medium and fluid of these tests, turbulence begins at a head gradient of about 0.1.
Influence of Natural Heterogeneity on the Efficiency of Chemical Floods in Source Zones
Authors: Ibaraki Motomu , Schwartz Franklin W. 
Published: December 2005

AbstractSeveral technologies for cleaning up DNAPLs in source zones rely on solubilizing contaminants or destroying them in situ. Typically, these approaches employ an injection/withdrawal system to recirculate this treatment fluids. Our interest is in examining factors that influence delivery efficiency. Although many factors can affect this efficiency, this study looks at the combined influence of density‐driven flow and porous media heterogeneities. The analysis is based on a series of numerical simulations of hypothetical chemical floods (e.g., potassium permanganate), which are highly resolved in space and time with a scale that is typical of field installations. Results indicate that the characteristics of convective mixing, i.e., natural, forced, and mixed convection, greatly affect delivery efficiency and patterns of mass transport. The ratio of the Grashof number (Gr) and Reynolds number (Re) proved useful in interpreting the patterns of flooding in a homogeneous porous medium. When higher‐permeability layers are included in the domain, they act as conduits, effectively expediting the transport of treatment chemicals from injection to recovery wells. These large fluxes of chemicals in the high‐permeability layers produce significant flooding inefficiencies. The problem is less severe in heterogeneous mediun where the connectivity through the treatment zone is less well developed. Overall, this paper illustrates that density effects and high‐permeability pathways need to be considered in designing chemical floods.
Hydraulic Head Applications of Flow Logs in the Study of Heterogeneous Aquifers
Authors: Paillet Frederick L. 
Published: December 2005

AbstractPermeability profiles derived from high‐resolution flow logs in heterogeneous aquifers provide a limited sample of the most permeable beds or fractures determining the hydraulic properties of those aquifers. This paper demonstrates that flow logs can also be used to infer the large‐scale properties of aquifers surrounding boreholes. The analysis is based on the interpretation of the hydraulic head values estimated from the flow log analysis. Pairs of quasi‐steady flow profiles obtained under ambient conditions and while either pumping or injecting are used to estimate the hydraulic head in each water‐producing zone. Although the analysis yields localized estimates of transmissivity for a few water‐producing zones, the hydraulic head estimates apply to the far‐field aquifers to which these zones are connected. The hydraulic head data are combined with information from other sources to identify the large‐scale structure of heterogeneous aquifers. More complicated cross‐borehole flow experiments are used to characterize the pattern of connection between large‐scale aquifer units inferred from the hydraulic head estimates. The interpretation of hydraulic heads in situ under steady and transient conditions is illustrated by several case studies, including an example with heterogeneous permeable beds in an unconsolidated aquifer, and four examples with heterogeneous distributions of bedding planes and/or fractures in bedrock aquifers.
Initial Yield to Depth Relation for Water Wells Drilled into Crystalline Bedrock—Pinardville Quadrangle, New Hampshire
Authors: Drew Lawrence J. , Schuenemeyer John H. , Armstrong Thomas R. , Sutphin David M. 
Published: December 2005

AbstractA model is proposed to explain the statistical relations between the mean initial water well yields from eight time increments from 1984 to 1998 for wells drilled into the crystalline bedrock aquifer system in the Pinardville area of southern New Hampshire and the type of bedrock, mean well depth, and mean well elevation. Statistical analyses show that the mean total yield of drilling increments is positively correlated with mean total well depth and mean well elevation. In addition, the mean total well yield varies with rock type from a minimum of 46.9 L/min (12.4 gpm) in the Damon Pond granite to a maximum of 74.5 L/min (19.7 gpm) in the Permian pegmatite and granite unit. Across the eight drilling increments that comprise 211 wells each, the percentages of very low‐yield wells (1.9 L/min [0.5 gpm] or less) and high‐yield wells (151.4 L/min [40 gpm] or more) increased, and those of intermediate‐yield wells decreased. As housing development progressed during the 1984 to 1998 interval, the mean depth of the wells and their elevations increased, and the mix of percentages of the bedrock types drilled changed markedly.The proposed model uses a feed‐forward mechanism to explain the interaction between the increasing mean elevation, mean well depth, and percentages of very low‐yielding wells and the mean well yield. The increasing percentages of very low‐yielding wells through time and the economics of the housing market may control the system that forces the mean well depths, percentages of high‐yield wells, and mean well yields to increase. The reason for the increasing percentages of very low‐yield wells is uncertain, but the explanation is believed to involve the complex structural geology and tectonic history of the Pinardville quadrangle.
Delineating Depth to Bedrock Beneath Shallow Unconfined Aquifers: A Gravity Transect Across the Palmer River Basin
Authors: Bohidar Rabi N. , Sullivan Jeffrey P. , Hermance John F. 
Published: December 2005

AbstractIn view of the increasing demand on ground water supplies in the northeastern United States, it is imperative to develop appropriate methods to geophysically characterize the most widely used sources of ground water in the region: shallow unconfined aquifers consisting of well‐sorted, stratified glacial deposits laid down in bedrock valleys and channels. The gravity method, despite its proven value in delineating buried bedrock valleys elsewhere, is seldom used by geophysical contractors in this region. To demonstrate the method's effectiveness for evaluating such aquifers, a pilot study was undertaken in the Palmer River Basin in southeastern Massachusetts.Because bedrock is so shallow beneath this aquifer (maximum depth is 30 m), the depth‐integrated mass deficiency of the overlying unconsolidated material was small, so that the observed gravity anomaly was on the order of 1 milligal (mGal) or less. Thus data uncertainties were significant. Moreover, unlike previous gravity studies elsewhere, we had no a priori information on the density of the sediment. Under such circumstances, it is essential to include model constraints and weighted least‐squares in the inversion procedure. Among the model constraints were water table configuration, bedrock outcrops, and depth to bedrock from five water wells. Our procedure allowed us to delineate depth to bedrock along a 3.5 km profile with a confidence interval of 1.8 m at a nominal depth of 17 m. Moreover, we obtained a porosity estimate in the range of 39% to 44%. Thus the gravity method, with appropriate refinements, is an effective tool for the reconnaissance of shallow unconfined aquifers.
A Nested Rediscretization Method to Improve Pathline Resolution by Eliminating Weak Sinks Representing Wells
Authors: Spitz Frederick J. , Nicholson Robert S. , Pope Daryll A. 
Published: December 2005

AbstractThis paper discusses a method for overcoming the problem of weak sinks representing wells that result from spatial discretization effects when using MODPATH, the particle‐tracking postprocessor for the ground water low model MODFLQW. Weak sink cells are model cells that represent a well that does not discharge at a sufficiently large rate to capture all of the flow entering the cell; therefore, flowpaths within these cells cannot be uniquely defined because it is impossible to know whether a given water particle discharges to the well or passes through the cell. Creating a submodel of the well cell by using the nested rediscretization method can eliminate this ambiguity by converting the weak sink cell into a strong sink cell. The method is designed to be run manually for each well and for steady‐state conditions. Other advantages, disadvantages, technical considerations, and limitations of the method are presented. Software created for the method consists of five Fortran programs that are operated using a set of instructions. A practical application of the method is presented by using an example wellhead‐protection problem that demonstrates that nested rediscretization can provide more accurate particle‐tracking results than those obtained by using a coarsely discretized model alone.