bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slug Tests in Unconfined Formations: An Assessment of the Bouwer and Rice Technique
Authors: Hyder Z. , Butler J. J. 
Published: August 2005

AbstractThe slug test is one of the most common techniques for the in situ estimation of hydraulic conductivity in unconfined flow systems. Recently, a mathematical model describing the flow of ground water in response to a slug test in an unconfined flow system has been proposed. This model incorporates the effects of partial penetration, anisotropy, an upper constant‐head boundary, and, in its most complete form, well skins of either higher or lower permeability than the formation itself. This model is useful in identifying conditions when conventional approaches (i.e., the Bouwer and Rice model) introduce large errors into parameter estimates. For slug tests performed in homogeneous, isotropic formations that would be classified as aquifers, the Bouwer and Rice model provides estimates within 30% of actual field values. In less‐permeable, clay‐rich formations, however, estimates may overpredict formation conductivity by more than 100%. The Bouwer and Rice model introduces the largest error (can easily exceed an order of magnitude) in the presence of a low‐permeability skin. Uncertainty about anisotropy can also be the source of considerable error. The semianalytical solution to the mathematical model described here can be employed for parameter estimation under conditions when the Bouwer and Rice model introduces unacceptably large errors into parameter estimates. This solution can be rapidly evaluated, allowing easy incorporation into an automated well‐test analysis package and/or ready generation of type curves.
Effective Parameter Optimization for Ground‐Water Model Calibration
Authors: Olsthoorn T. N. 
Published: August 2005

AbstractThis paper shows that the Levenberg‐Marquardt method, modified to limit the parameter update steps to within a specified range, effectively optimizes a set of parameters in a ground‐water model. In doing so it performs better than more complicated conjugate gradient algorithms.The method has been applied to the synthetic ground‐water problem of Carrera and Neuman (1986b), which has been used previously to test calibration method performance. The descent of the error criterion and the simultaneous approach of the parameters to their optimum values are smooth, both with perfect and erroneous head observation data.It is shown that least‐squares optimization can be done effectively in a simple manner and that it can be easily integrated with practical ground‐water modeling. No changes have to be made to the model code. This ease of implementation is emphasized by the fact that all modeling presented here was done using an ordinary spreadsheet program on a PC.
Optimal Ground‐Water Remediation Methods Applied to a Superfund Site: From Formulation to Implementation
Authors: Ahlfeld David P. , Page Roger H. , Pinder George F. 
Published: August 2005

1. AbstractA hydraulic control optimization model is applied to the conceptual and implementation analysis of a ground‐water remediation system in coastal New Jersey. The site is modeled using a distributed parameter finite‐difference model containing 36,000 nodes within five layers. The conceptual problem is to determine the feasibility of producing a capture zone which encompasses the entire existing plume while recharging all extracted water within property boundaries in such a way that the recharged water satisfies criteria on its fate. The conceptual analysis problem is formulated as a linear program in which the total extraction pumping is minimized, and requirements are placed on hydraulic heads and gradients in both horizontal and vertical directions. A requirement is also made that all extracted water be recharged to the subsurface. The model is used for determination of the feasibility of the remediation concept. Details of constructing constraints for a large‐scale formulation are presented. The concept of constraint calibration, using particle tracking to insure that constraints are producing desired results, is introduced and demonstrated. The optimization formulation is used for detailed implementation analysis of the remediation system. A number of techniques for modifying elements of the conceptual model results, such as unrealistically small pump rates, are described. The optimization approach is found to be useful for determining the feasibility of the remedial strategy at this site and for producing results which can be used as a starting point for detailed analysis of the remediation strategy.
Geothermal‐Water Characteristics in the Surdulica Aquifer
Authors: Hadzisehović Munevera , Dangić Adam , Miljević Nada , Sipka Vojislava , Golobocanin Dusan 
Published: August 2005

AbstractThe Surdulica‐Bujanovac geothermal region of southeastern Serbia, with granodiorite (Surdulica) and granite (Bujanovac) aquifers (water temperatures of 125°C and 46°C, respectively) was hydrogeologically and geochemically studied using environmental isotopes from 1986 to 1990. In the Surdulica system, water, rock, and vegetation samples from 35 locations (springs, rivers, and boreholes) representing all parts of the hydrogeological system (recharge area, transition zone, and terminus with hot deep‐circulated waters) were collected for geochemical and isotope analyses (D, 18O,3H, 13C, 14C). From the recharge area to the terminus of the system, ground‐water temperatures and ionic concentrations increase two to three orders of magnitude: temperature from 3–126°C, Na+ 2.3–1127 mg/1; HCO3− 30.5–2989 mg/1; SO42− 4.8–480 mg/1; SiO2 3–90 mg/1. The hot waters, appearing at the terminus of the system (Vranjska and Bujanovac Spas locations) are the oldest, based on 14C and 3H. The δ13C attains the low negative value of −0.4‰ for hot waters, approaching those in the aquifer matrix, which are in the range between −8.4 and + 2 ‰. The δ18O and δD values in precipitation and ground water indicate that recharge takes place predominantly at the higher elevations (more than 500 m asl) and in the cold seasons. A dual‐porosity system comprised of fissures and intergranular storage controls fluid transport. The deepest flows are hydraulically isolated from fresh waters. Low 14C contents (1–6 pMC) and the absence of3 H suggest the mean residence times for the older water up to 20,000 years. A 18O shift and chemical geothermometers suggest that their base temperatures of more than 200°C are not likely.
Fracture Density Distributions and Well Yields in Coastal Maine
Authors: Loiselle Marc , Evans David 
Published: August 2005

AbstractUnderstanding the distribution of water‐bearing fractures in crystalline rock is an important component in evaluating the availability and vulnerability of water resources throughout the northeastern U.S. The State of Maine requests well drillers to report estimates of fracture depths and fracture yields for all bedrock wells drilled in the state. Using these data we analyze fracture‐depth and fracture‐yield data from 227 bedrock wells in coastal Maine in order to understand how fracture locations and yields are distributed with depth. Numerical simulations and statistical tests show that it is not possible to infer how fractures are distributed with depth: fracture depths are consistent with several distributions, including uniform fracture density with depth. In order to understand how fracture yield varies with depth, we group yield data into 50 foot depth intervals and compare distributions in each interval using nonparametric statistical tests. These tests show that the distribution of fracture yield in different depth intervals are statistically equivalent. These results imply that there is no empirical justification for limiting well depth when drilling for water resources in fractured bedrock in coastal Maine.
Analytical Solutions for Water Flow and Solute Transport in the Unsaturated Zone
Authors: Nachabe Mahmood H. , Islas Alvaro L. , Illangasekare Tissa H. 
Published: August 2005

AbstractAnalytical solutions for the water flow and solute transport equations in the unsaturated zone are presented. We use the Broadbridge and White nonlinear model to solve the Richards’ equation for vertical flow under a constant infiltration rate. Then we extend the water flow solution and develop an exact parametric solution for the advection‐dispersion equation. The method of characteristics is adopted to determine the location of a solute front in the unsaturated zone. The dispersion component is incorporated into the final solution using a singular perturbation method. The formulation of the analytical solutions is simple, and a complete solution is generated without resorting to computationally demanding numerical schemes. Indeed, the simple analytical solutions can be used as tools to verify the accuracy of numerical models of water flow and solute transport. Comparison with a finite‐element numerical solution indicates that a good match for the predicted water content is achieved when the mesh grid is one‐fourth the capillary length scale of the porous medium. However, when numerically solving the solute transport equation at this level of discretization, numerical dispersion and spatial oscillations were significant.
Dampening of Transverse Dispersion in the Halocline in Karst Limestone in the Northeastern Yucatan Peninsula
Authors: Stoessell Ronald K. 
Published: August 2005

AbstractA range of hydrodynamic dispersion coefficients was estimated for fracture‐fluid and combined fracture and pore‐fluid flow within the halocline of the limestone aquifer forming the surface of the northern Yucatan Peninsula. The coefficients are fit parameters in a model reproducing observed halocline profiles in a sinkhole and in a borehole near the northeastern coast. Fitted coefficients range from 10−7 to 10−4 cm2/sec, of which molecular diffusion, without transverse (vertical) dispersion, can account for 10−7 to 10−5 cm2/sec. The mechanical stability of the vertical density gradient in the halocline dampens transverse dispersion in pore fluids and in fracture fluids that are transitional between laminar and turbulent flow. The dampening is proportional to the ratio of the energy needed for the fluid to rise and displace a less dense fluid to the vertical component of the kinetic energy of the fluid. The ratio of these two energies is at a maximum during the initial stage of development of a halocline and decreases as the halocline widens.
Retardation of Dissolved Oxygen Due to a Trapped Gas Phase in Porous Media
Authors: Fry Virginia A. , Istok Jonathan D. , Semprini Lewis , O'Reilly Kirk T. , Buscheck Timothy E. 
Published: August 2005

AbstractInformation on the transport of dissolved gases in ground water is needed to design ways to increase dissolved gas concentrations in ground water for use in in situ bioremediation (e.g., O2 and CH4) and to determine if dissolved gases are conservative tracers of ground‐water flow (e.g., He). A theoretical model was developed to describe the effect of small quantities of trapped gas bubbles on the transport of dissolved gases in otherwise saturated porous media. Dissolved gas transport in porous media can be retarded by gas partitioning between the mobile aqueous phase and a stationary trapped gas phase. The model assumes equilibrium partitioning where the retardation factor is defined as R = 1 + H′(Vg/Vw) where H' is the dimensionless Henry's Law constant for the dissolved gas, and Vg and Vw are the volumes of the trapped gas and water phases, respectively. At 15°C and with Vg/ Vw= 0.05, the predicted retardation factors for He, O2, and CH4 are 5.8, 2.4, and 2.3, respectively. The validity of the model was tested for dissolved oxygen in small‐scale column experiments over a range of trapped gas volumes. Retardation factors of dissolved oxygen increased from 1 to 6.6 as Vg/Vw increased from 0 to 0.123 and are in general agreement with model predictions except for the larger values of Vg/Vw. The theoretical and experimental results suggest that gas partitioning between the aqueous phase and a trapped gas phase can greatly influence rates of dissolved gas transport in ground water.
Flow of Gasoline‐in‐Water Microemulsion Through Water‐Saturated Soil Columns
Authors: Ouyang Ying , Mansell Robert S. , Rhue R. Dean 
Published: August 2005

AbstractMuch consideration has been given to the use of surfactants to clean up nonaqueous phase liquids (NAPLs) from contaminated soil and ground water. Although this emulsification technique has shown significant potential for application in environmental remediation practices, a major obstacle leading to low washing efficiency is the potential formation of macroemulsions with unfavorable flow characteristics in porous media. This study investigated influences of the flow of leaded‐gasoline‐in‐water (LG/W) microemulsion upon the transport of gasoline and lead (Pb) species in water‐saturated soil columns. Two experiments were performed: (1) the immiscible displacement of leaded gasoline and (2) the miscible displacement of LG/W microemulsion through soil columns, followed by sequentially flushing with NaCl solution and a water/surfactant/cosurfactant (W/S/CoS) mixture. Comparison of breakthrough curves (BTC) for gasoline between the two experiments shows that about 90% of gasoline and total Pb were removed from the soil columns by NaCl solution in the LG/W microemulsion experiment as compared to 40% removal of gasoline and 10% removal of total Pb at the same process in the leaded gasoline experiment. Results indicate that gasoline and Pb species moved much more effectively through soil during miscible flow of LG/W microemulsion than during immiscible flow of leaded gasoline. In contrast to the adverse effects of macroemulsion on the transport of NAPLs, microemulsion was found to enhance the transport of gasoline through water‐saturated soil. Mass balance analysis shows that the W/S/CoS mixture had a high capacity for removing residual gasoline and Pb species from contaminated soil. Comparison of water‐pressure differences across the soil columns for the two experiments indicates that pore clogging by gasoline droplets was greatly minimized in the LG/W microemulsion experiment.
Estimating DNAPL Composition and VOC Dilution from Extraction Well Data
Authors: Jackson R. E. , Marine P. E. 
Published: August 2005

AbstractField data from a large‐scale ground‐water extraction system at the Savannah River Site in South Carolina indicate that considerable dilution of volatile organic compounds (VOCs) occurs at extraction wells when compared with the effective solubilities of the VOC components (TCE and PCE) in the dense, nonaqueous phase liquid (DNAPL) source zone. This dilution is believed to be due to the convergence of both contaminated and uncontaminated streamtubes on the extraction wells studied. Thus, the measured concentrations of dissolved VOCs in extraction wells appear to be principally functions of (1) the effective solubilities of the DNAPL components, and (2) the dilution due to streamtube convergence on the extraction wells. A simple method for computing DNAPL composition and the dilution factor from extraction well data is presented for the case when dilution is the dominant mechanism that causes the measured ground‐water concentrations of dissolved VOC components to be significantly less than their respective effective solubilities relative to the DNAPL mixture. This method successfully computes the molar composition of a PCE/ TCE DNAPL, bailed from a pair of monitor wells at the Savannah River Site, using the measured concentrations of PCE and TCE in ground waters from the same pair of wells. The method is then used to predict the variation of DNAPL composition within the aquifer from VOC data sampled at all 11 extraction wells. Such information is of considerable use in choosing solvent‐specific surfactants for enhanced remediation operations.
Measurements of Aquifer‐Storage Change and Specific Yield Using Gravity Surveys
Authors: Pool D. R. , Eychaner J. H. 
Published: August 2005

AbstractPinal Creek is an intermittent stream that drains a 200‐square‐mile alluvial basin in central Arizona. Large changes in water levels and aquifer storage occur in an alluvial aquifer near the stream in response to periodic recharge and ground‐water withdrawals. Outflow components of the ground‐water budget and hydraulic properties of the alluvium are well‐defined by field measurements; however, data are insufficient to adequately describe recharge, aquifer‐storage change, and specific‐yield values. An investigation was begun to assess the utility of temporal‐gravity surveys to directly measure aquifer‐storage change and estimate values of specific yield.The temporal‐gravity surveys measured changes in the differences in gravity between two reference stations on bedrock and six stations at wells; changes are caused by variations in aquifer storage. Specific yield was estimated by dividing storage change by water‐level change. Four surveys were done between February 21, 1991, and March 31, 1993. Gravity increased as much as 158 microGal ± 1 to 6 microGal, and water levels rose as much as 58 feet. Average specific yield at wells ranged from 0.16 to 0.21, and variations in specific yield with depth correlate with lithologic variations. Results indicate that temporal‐gravity surveys can be used to estimate aquifer‐storage change and specific yield of water‐table aquifers where significant variations in water levels occur. Direct measurement of aquifer‐storage change can eliminate a major unknown from the ground‐water budget of arid basins and improve residual estimates of recharge.
Use of a Square‐Array Direct‐Current Resistivity Method to Detect Fractures in Crystalline Bedrock in New Hampshire
Authors: Lane J. W. , Haeni F. P. , Watson W. M. 
Published: August 2005

AbstractAzimuthal square‐array direct‐current (dc) resistivity soundings were used to detect fractures in bedrock in the Mirror Lake watershed in Grafton County, New Hampshire. Soundings were conducted at a site where crystalline bedrock underlies approximately 7 m (meters) of glacial drift. Measured apparent resistivities changed with the orientation of the array. Graphical interpretation of the square‐array data indicates that a dominant fracture set and (or) foliation in the bedrock is oriented at 030° (degrees). Interpretation of crossed square‐array data indicates an orientation of 027° and an anisotropy factor of 1.31. Assuming that anisotropy is due to fractures, the secondary porosity is estimated to range from 0.01 to 0.10.Interpretations of azimuthal square‐array data are supported by other geophysical data, including azimuthal seismic‐refraction surveys and azimuthal Schlumberger dc‐resistivity soundings at the Camp Osceola well field. Dominant fracture trends indicated by these geophysical methods are 022° (seismic‐refraction) and 037° (dc‐resistivity). Fracture mapping of bedrock outcrops at a site within 250 m indicates that the maximum fracture‐strike frequency is oriented at 030°.The square‐array dc‐resistivity sounding method is more sensitive to a given rock anisotropy than the more commonly used Schlumberger and Wenner arrays. An additional advantage of the square‐array method is that it requires about 65 percent less surface area than an equivalent survey using a Schlumberger or Wenner array.
Research Borehole‐Geophysical Logging in Determining Geohydrologic Properties
Authors: Jorgensen Donald G. , Petricola Mario 
Published: August 2005

AbstractA research borehole‐geophysical logging program was implemented to assess specific yield, aquifer mineralogy, and water resistivity more accurately and economically than can be done using conventional aquifer testing and coring procedures. The logging program was part of the Ground‐Water Research Project for Abu Dhabi Emirate.A method of determining specific yield using data from a thermal decay‐time (TDT) log was developed and tested. This technique relates the capture cross section of the fluid in the invaded zone to specific yield. A second new method uses data from density and neutron logs in a program “LOGAN2” to determine specific yield. Results from both methods were compared to the specific yield derived from the neutron log as well as a specific yield determined by a complex analysis of data from a set of research borehole‐geophysical logs, including a gamma‐gamma log for density, neutron, sonic, gamma‐ray, induction, microresistivity, photoelectric, caliper, and spontaneous‐potential logs. The agreement was good.A method of computer‐assisted interpretation of mineralogy was developed by correlating results of direct examination of the mineralogy of sidewall cores with data from a nuclear activated spectral‐gamma log (GLT). The GLT log allows the mineralogy to be assessed in a comprehensive manner. These computer interpreted results were used to develop another method of computer‐assisted interpretation of holes logged not using the GLT. The second method was applied to the more than 50 other test holes that did not include GLT and TDT logs.Resistivity of the water in the formation was conceptualized using a dual‐water model, which is especially suited for clayey aquifers. Water resistivities were calculated by two methods—first using data from the suite of logs without the GLT and again using the data from the research suite of logs, which included the GLT. The agreement of calculated water resistivities was excellent
Bottled Water, Spas, and Early Years of Water Chemistry”
Authors: Back William , Landa Edward R. , Meeks Lisa 
Published: August 2005

AbstractAlthough hot springs have been used and enjoyed for thousands of years, it was not until the late 1700s that they changed the course of world civilization by being the motivation for development of the science of chemistry. The pioneers of chemistry such as Priestley, Cavendish, Lavoisier, and Henry were working to identify and generate gases, in part, to determine their role in carbonated beverages. In the 18th century, spas in America were developed to follow the traditional activities of popular European spas. However, they were to become a dominant political and economic force in American history on three major points: (1) By far the most important was to provide a place for the leaders of individual colonies to meet and discuss the need for separation from England and the necessity for the Revolutionary War; (2) the westward expansion of the United States was facilitated by the presence of hot springs in many locations that provided the economic justification for railroads and settlement; and (3) the desire for the preservation of hot springs led to the establishment of the National Park Service. Although mineral springs have maintained their therapeutic credibility in many parts of the world, they have not done so in the United States. We suggest that the American decline was prompted by: (1) the establishment of The Johns Hopkins School of Medicine in 1893; (2) enactment of the Pure Food and Drug Act of 1907; and (3) the remarkable achievement of providing safe water supplies for American cities by the end of the 1920s. The current expanding market for bottled water is based in part on bottled water being an alternative beverage Ito alcohol and sweetened drinks and the inconsistent palatability and perceived health hazards of some tap waters.