bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gravity Delineation of a Buried Valley in Quartzite
Authors: Hansen Donald S. 
Published: March 2006

ABSTRACTA gravity survey was conducted in a 94‐square‐mile area of northeastern Hanson County, South Dakota. The 340 measured gravity values, together with test‐hole data, were used to approximately delineate a buried valley eroded into the Sioux Quartzite of Precambrian age. This valley contains, in places, an aquifer composed of quartzose sand of pre‐Cretaceous age derived from the Sioux Quartzite. The bottom of the valley is approximately 450–600 ft below land surface. Simple Bouguer values were determined from measured gravity data, referenced to a local base station, and interpolated to a 0.5‐ by 0.5‐mile grid. The interpolated simple Bouguer values of residual gravity were determined using a five‐ring, inverse‐weighted filtering method. The second derivative of the interpolated gravity values, as well as their downward continuation, did not delineate the buried valley as well. Subsequent drilling of nine test holes showed that the gravity method can be used for approximately delineating subsurface features
TOC Determinations in Ground Water
Authors: Barcelona Michael J. 
Published: March 2006

ABSTRACTDeterminations of total organic carbon (TOC) can provide valuable diagnostic evidence of the extent of ground‐water contamination by organic compounds. The usefulness of conventional TOC results in monitoring efforts is limited by the bias introduced during the purging of inorganic carbon prior to analysis. A modified TOC procedure has been evaluated to permit the quantitation of the volatile organic carbon (VOC) fraction in water samples. The methodology consists of trapping the VOC in a manner analogous to commercial purge and trap instruments which are used for specific organic compound separations. The method has been found to be sensitive, accurate and reasonably precise for TOC determinations of standard solutions as well as on ground‐water samples. Volatile organic carbon levels can range from 9–50% of the TOC in both uncontaminated and contaminated ground waters. The reporting of the volatile and nonvolatile fractions of the TOC will enhance both monitoring and research efforts, since it permits more complete characterization of the organic carbon content of ground‐water samples.
A Routing Technique for Estimating Ground–Water Recharge
Authors: Senarath D.C.H. , Rushton K. R. 
Published: March 2006

ABSTRACTA technique is presented for the estimation of ground–water recharge in a region where the formations overlying an aquifer cannot transmit all of the available water to the aquifer. The method is based on a routing model which is derived from the physical nature of formations overlying the aquifer. The model takes into account precipitation, evapotranspiration, soil moisture balance and the passage of water through strata such as boulder clay. The validity of the model is tested by calculated and field stream flow hydrographs.
Observed Drawdown Pattern Around a Well Partially Penetrating a Vertically Extensive Water‐Table Aquifer
Authors: Sayed Shabbir A. S. 
Published: March 2006

ABSTRACTIn order to understand the flow pattern around a pumping well partially penetrating a vertically extensive aquifer, a specially designed pumping test was carried out in Pakistan. In this paper salient features of the test have been described. The spatial distributions of drawdown have been shown graphically. Some of the preliminary conclusions made from the drawdown pattern include:

The distance beyond which the flow is likely to be horizontal increases with decrease in the degree of aquifer penetration.
In equidistant observation wells open at different depths, (1) the drawdowns tend to merge at larger times, provided the observation point is located within the screened section of the aquifer; (2) the less the depth of penetration is, the earlier the drawdowns start merging; and (3) the initial rate of drawdown near the aquifer top is slow but catches up with time to exceed those at deeper points.
A Study on Confined Flow of Ground Water Through a Tunnel
Authors: Chisyaki Takeshi 
Published: March 2006

ABSTRACTConfined flow of ground water through a tunnel, which might be encountered in tunneling under the bottom of a sea or river, is numerically analyzed by a reductive finite element method formulated in our research. That is, the rate and potential distribution of the confined flow of ground water through an opening are obtained in connection with the permeability of rock masses, the thickness of covered ground, the location of impermeable bedrock, and other variables.In addition, flow through an opening in the ground with highly permeable masses and discharge of ground water through a tunnel in grouted masses are illustrated, and some useful results for the practical application of tunneling work are obtained.
A Model of Regional Ground‐Water Flow in Secondary‐Permeability Terrane
Authors: Gerhart James M. 
Published: March 2006

ABSTRACTThe ground‐water flow system in the Lower Susquehanna River Basin in Pennsylvania and Maryland can be considered as one complex unconfined aquifer in which secondary porosity and permeability are the dominant influences on the occurrence and flow of ground water. The degree of development of secondary porosity and permeability in the various lithologies of the lower basin determines the aquifer characteristics of each lithology. Based on qualitative evidence, the use of a porous‐media model was assumed to be appropriate on a regional scale and a finite‐difference ground‐water flow model was constructed for the lower basin.The conceptual model of ground‐water flow in the lower basin incorporates the major features of the flow system. Through the use of two layers, 21 hydrogeologic units, and five topographic settings, the conceptual model was systematically reduced to arrive at a simplified conceptual model. Further reduction produced a numerical model representation of the conceptual model, in which the essential features of the lower‐basin flow system were quantified for input into the numerical model.The model was calibrated under both steady‐state and transient conditions, and was used to evaluate the water‐supply potential of the 21 hydrogeologic units. The carbonate units have the greatest potential for ground‐water development and the Triassic sedimentary and crystalline units have the least potential. A total ground‐water yield potential of about 900 million gallons per day could be obtained from the lower basin with a consequent 50‐percent reduction of base flow in streams.
Contamination of an Unconfined Sand Aquifer by Waste Pulp Liquor: A Case Study
Authors: Robertson W. D. , Barker J. F. , LeBeau Y. , Marcoux S. 
Published: March 2006

ABSTRACTA zone of contaminated ground water has been identified in an unconfined sand aquifer adjacent to a pit into which spent pulp liquor was intermittently discharged from 1970 to 1979. A network of multilevel sampling, bundle‐type piezometers was installed. Up to seven depthspecific sampling points were incorporated into each piezometer providing a cost‐effective means for three‐dimensional mapping of hydraulic head and water quality in the unconfined sand aquifer. Ground‐water samples retrieved from this network showed an area of contamination 900 m long, 400 m wide, and more than 25 m deep. This plume is dispersed about the ground‐water flow lines passing beneath the waste disposal pit, and it terminates at a vigorous ground‐water discharge area located 800 m from the pit.The contaminated ground water is characterized by elevated concentrations of sodium (3,000 mg/1), chloride (590 mg/1), alkalinity (2,700 mg/1), total organic carbon (2,000 mg/1), chemical oxygen demand (10,800 mg/1), biological oxygen demand (2,000 mg/1), tannin and lignin (780 mg/1), and lower sulphate (1 mg/1) compared to background ground waters in the area. The apparent rate of sodium migration is more than 50 m/yr and is close to the average linear ground‐water velocity. Removal of some organic matter by biological transformation has produced the increased alkalinity in the contaminated ground water and somewhat reduced pH. Tannin and lignin are relatively inert compared to other organic compounds found in the waste liquor. Extremely low sulphate levels occurring in the highly contaminated ground waters indicate the existence of conditions favorable for microbially‐mediated sulphate reduction.
Evolution of Regional Hydrogeologic Setup of a Hard Rock Aquifer Through R‐C Analog Model
Authors: Gupta C. P. , Thangarajan M. , Rao V.V.S. Gurunadha 
Published: March 2006

ABSTRACTConceptualization of regional hydrogeologic setup in a hard rock granitic terrain by employing sparse data obtained through conventional methods is usually not possible. In such situations, aquifer simulation could be employed as a useful tool. An attempt was made to evolve the regional pattern of hydrogeologic parameters in a granitic basin. During the process of model calibration, the field estimates of hydrogeological parameters as well as those of recharge and ground‐water extraction were appropriately modified. A first‐order estimate of the effluent outflow from the aquifer to ephemeral streams was made only from the flow model. The calibrated model satisfactorily reproduced the historical response of the aquifer and could be used for prognosis.
Automatic Generation of Flow Nets with Conventional Ground‐Water Modeling Algorithmsa
Authors: Fogg Graham E. , Senger R. K. 
Published: March 2006

ABSTRACTThough flow nets offer one of the best means of visualizing ground‐water flow fields, accurate construction of flow nets can be very difficult in heterogeneous, anisotropic media or in regional cross sections where vertical exaggeration of scale is great. A method was developed for automatically generating the streamlines of a flow net using conventional ground‐water flow modeling algorithms. The method can be implemented using most any of the existing computer programs for flow modeling, and no modification of the programs is necessary. One need only replace the hydraulic head and conductivity terms in the steady‐state ground‐water flow equation with the stream function and an inverse form of hydraulic conductivity, respectively. Possible boundary conditions include prescribed stream function (Dirichlet type) and prescribed stream function gradient (Neumann type). The former can be determined from prior knowledge of recharge or discharge rates or from boundary fluxes computed in previous simulations of hydraulic head distribution. The latter can be determined from data on hydraulic head along the boundaries, raising the possibility of solving for the streamlines directly without first solving for the head distribution. The method is generally not appropriate when sources or sinks occur inside the flow region, and it will not handle transient conditions. Accuracy of the method is demonstrated in three hypothetical test problems and a vertical‐plane model through the Palo Duro Basin of Texas and New Mexico.
THE POWER OF THE ELECTRONIC WORKSHEET: MODELING WITHOUT SPECIAL PROGRAMS
Authors: Olsthoorn T. N. 
Published: March 2006

Abstract. So‐called spreadsheet programs are forerunners of new general software from which the ground‐water engineer is likely to benefit–no more special programs each capable of fulfilling just that single task it was explicitly designed for, but programs suitable to do almost any job, where only the fantasy of the user limits the possibilities. Moreover, this new software shows us what user friendliness looks like and proves that it is completely superfluous to be a computer specialist to use it.With a spreadsheet you can build a simple finite‐difference model from scratch within one or two minutes. With some extra time a wide versatility of problems can be solved as the multiaquifer, three‐dimensional, phreatic and transient ground‐water flow examples prove. This way any hydrologist should be able to solve diverging ground‐water models himself without depending on special numerical models. All he needs beyond a microcomputer and a spreadsheet program is a good knowledge of the water balance.
Gradient Controlled Caves, Trapper‐Medicine Lodge Area, Bighorn Basin, Wyoming
Authors: Huntoon Peter W. 
Published: March 2006

ABSTRACTExtensive caves have developed under canyons in the Trapper‐Medicine Lodge recharge area where ground‐water flow rates became maximized within the Madison carbonates during Cenozoic time. The large flow rates resulted directly from the superposition of steep local gradients on the ground‐water circulation system as a consequence of the erosion of confining units in the region. The cave forming process in this area is gradient controlled, a conclusion that has possible applicability elsewhere.
An Interpretation of Dug Well Performance Using a Digital Model
Authors: Lawrence A. R. 
Published: March 2006

ABSTRACTDug wells in the Deccan basalts of India can provide a means of determining the permeability of the unconfined aquifer within the weathered layer. The layered nature of this aquifer, together with its low permeability, produces a complicated ground‐water flow pattern around large‐diameter dug wells when they are pumped. A digital model, which successfully simulated the head distribution in and around a large‐diameter pumping well demonstrated that recovery, rather than drawdown, data from such tests are more suitable for analysis.
Some Computational Experiences Using Embedding Technique for Ground‐Water Management
Authors: Tung Yeou‐Koung , Koltermann Christine E. 
Published: March 2006

ABSTRACTA distributed parameter ground‐water management model was developed using finite‐difference approximations of the governing partial differential equation for ground‐water flow in a confined aquifer. The resulting system of simultaneous equations was embedded in an optimization model, which used hydraulic heads and pumpages as unknown state variables and decision variables, respectively. The model was applied to several hypothetical examples of varying size and complexity and to one real‐world example, the Las Vegas Valley aquifer. The grid spacing, time increment, bounds placed on pumpage, and the number of constraints were found to affect not only the execution time, but also whether the model would execute at all.In order to accommodate long‐term management goals, a lumped transient model should be used which incorporates all time periods the model encompasses. Some objective functions, such as the maximization of the head, can be executed in a stepwise manner in which the final heads from the current period are used as the initial heads for the next period. The embedding technique proved useful for small management problems, but had numerical difficulties with the large real‐world problems of considerable heterogeneity. Unless the embedding technique can become computationally efficient and stable, it should be bypassed in favor of the response matrix approach.
A Model Study of Salt‐Water Intrusion to a River Using the Sharp Interface Approximation
Authors: McElwee C. D. 
Published: March 2006

ABSTRACTBetween Salina and Enterprise, Kansas, the salinity of the Smoky Hill River increases sharply. As a result, the river downstream at various times exceeds the recommended drinking‐water‐quality standards for chloride. The Smoky Hill and Kansas Rivers are important sources of water for several population centers in eastern Kansas. Therefore, this problem has an impact on a significant part of the Kansas population. The source of the saline water is predominantly from ground‐water dissolution of the Hutchinson Salt Member of the Wellington Formation of Permian age. The dissolution of the salt has caused a north‐south trending collapsed zone called the Wellington aquifer to occur along the present eastern extent of the salt. A confining shale layer exists between the Smoky Hill alluvium and the Wellington aquifer in most areas. However, between New Cambria and Solomon, Kansas, the layer is thin and fractured, allowing the salt water to move up into the alluvium.The steady‐state model presented in this study indicates that the salt‐water layer of the alluvium in the Smoky Hill River valley should be in an unstable condition near the river. This indicates that unstable interface upconing should be a dominant mechanism for supplying salt water to the river system. The time‐varying model shows that the response of the chloride discharge to a flood event can be qualitatively explained by the unstable interface upconing mechanism. As the river stage rises, the salt‐water intrusion declines. As the river stage declines, the salt‐water intrusion increases beyond its normal value and subsides to the normal value over the period of a few months if no new flood events occur. During rising river stage, the river is supplying the ground‐water system, and the salt‐water intrusion or unstable upconing is shut off. During falling river stage, bank storage and perhaps an elevated water table cause the fresh ground‐water discharge to be greater than normal, which in turn causes greater than normal salt‐water intrusion. In addition, the time‐varying model shows that several years would elapse before significant benefit would be seen in the river system from a proposed Wellington aquifer relief‐well scheme.
A New Method of Contaminant Plume Analysis
Authors: Domenico P. A. , Robbins G. A. 
Published: March 2006

ABSTRACTThis paper develops an analytical expression for contaminant transport from a finite source in a continuous flow regime. The model requires some numerical integration and its degree of accuracy for near‐field problems depends on discretization procedures applied to the source boundary. A second model for a continuous source is developed by extending a well‐known pulse model. This second model is particularly useful in that it permits the determination of several potential unknowns directly from a concentration distribution. These include the source concentration, source dimensions, the position of the center of mass which is the product of the seepage velocity and the time since the contaminant first entered the ground water, and up to three dispersivities for a three‐dimensional problem. As a demonstration of its utility, this second model is applied with reasonable success to a well‐defined field condition. A comparison of the two models indicates that, except for minor differences in the very near field, the results from each are virtually identical.
Laboratory Investigation and Analysis of a Ground‐Water Flowmeter
Authors: Melville Joel G. , Molz Fred J. , Güven Oktay 
Published: March 2006

ABSTRACTThe ground‐water flowmeter system, model 3OL, manufactured by K‐V Associates Inc., Falmouth, Massachusetts was tested under controlled laboratory conditions. The influence of slotted pipe schedule, slot orientation, backfill materials, endcap bags, isolated regions of high hydraulic conductivity, and channelization near the slotted pipe wall was measured. The physical concept of the flow‐meter in an ideal configuration was analyzed, and with the aid of an analytical model, the significance of the thermal and hydraulic characteristics of the aquifer and backfill materials is clarified. Results indicate that the basic instrument response is linear, consistent, and predictable qualitatively in a laboratory environment. Analysis and measurements show clearly that very small channelization around a slotted pipe casing or between the slotted pipe and the probe endcap can invalidate the instrument response. Additional potential complications arise due to unknown permeability contrasts between the aquifer matrix and the material used to backfill around the probe.
Movement of Volatile Organics Through a Fractured Rock Aquifer
Authors: E.Spayd Steven 
Published: March 2006

ABSTRACTIn response to the detection of contaminants in several municipal water supply wells in a northern New Jersey community, the New Jersey Department of Environmental Protection (NJDEP) undertook a detailed assessment of the movement of volatile organics through the Brunswick fractured rock aquifer. Understanding the directional or anisotropic behavior of ground‐water flow within the aquifer proved to be a crucial factor for identification of the sources of contamination. Since the ground‐water flow occurs in a direction predominantly parallel to the strike of the aquifer, the resulting distribution of contaminants allowed the differentiation of two overlapping plumes, each over 4,000 feet in length and each emerging from discrete adjacent sources.The investigations and subsequent cleanup agreements between the NJDEP and the responsible parties allowed savings of several million dollars for the U.S. EPA's Super‐fund Program which otherwise would have been used for cleanup of the site. The privately funded cleanup program includes treatment of the affected municipal wells and on‐site remedial actions designed to fully restore the aquifer within 10 years.
Stable Carbon Isotopes of HCO3 in the Aquia Aquifer, Maryland: Evidence for an Isotopically Heavy Source of CO2
Authors: Chapelle Francis H. , Knobel LeRoy L. 
Published: March 2006

ABSTRACTConcentrations of HCO3 and δ13C values of dissolved inorganic carbon change along the hydrologic gradient of the Aquia aquifer. In the outcrop area, meteoric recharge rapidly dissolves carbonate shell material (δ13C ∼ 0.0 per mil) in the presence of soil‐gas CO2 (δ13C∼–26 per mil). HCO3 concentrations in this area range from 150‐200 mg/1 and δ13C values of dissolved HCO3 are approximately –13.0 per mil. Concentrations of HCO3 decrease gradually (to about 130 mg/1) and δ13C values become slightly heavier (to about –11.4 per mil) as water flows away from the outcrop area. These trends reflect progressive dissolution of metastable carbonate shell material and subsequent precipitation of secondary calcite cement. At about 40 miles downgradient in the flow system, HCO3 concentrations increase sharply (to about 400 mg/1), and δ13C values become significantly heavier (δ13C ∼–6.2 per mil). The observed 1:1 molar ratio of Na+ to HCO‐3 in this downgradient water shows that dissolution of isotopically heavy carbonate shell material cannot by itself explain the observed δ13C trend. Rather, the Na:HCO‐3 ratio demonstrates that shell material dissolution must take place in the presence of CO2. Because the aquifer in this area is closed to both soil‐gas and atmospheric CC>2, an aquifer‐generated source of isotopically heavy (δ13C ∼–5.3 per mil) CO2 is implied. Possible sources of aquifer‐generated CO2 include bacterially‐mediated fermentation of lignitic aquifer materials and bacterially‐mediated methanogenesis.
A Hydraulic Trap for Preventing Collector Well Contamination: A Case Study
Authors: Ophori Duke U. , Farvolden Robert N. 
Published: March 2006

ABSTRACTA hydraulic trap in the form of a purge well is proposed for the Forwell collector well K‐71. The trap, which will protect well K‐71 from contamination by contaminants migrating downgradient from the old Breslube waste disposal site, is based on a qualitative flow net obtained from a finite‐element model of the Forwell Aquifer. The trap constitutes pumping at the position of observation well OW 9‐80 at a continuous rate of at least 6.1 X 10‐3 m3/s. The uniqueness of the trap lies in its simplicity and relatively low cost.
Ground‐Water Model of Two‐Phase Immiscible Flow in Coarse Material
Authors: Hochmuth David P. , Sunada Daniel K. 
Published: March 2006

ABSTRACTA numerical model was developed to simulate the behavior of two‐phase immiscible fluids in ground‐water systems for specific application to hydrocarbon spills and leaks. The model is a two‐dimensional areal flow model using the finite‐element method. A verification of the numerical model was performed using both an approximate analytical solution and a laboratory investigation. The verification results show that the numerical model adequately describes the behavior of immiscible two‐phase flow within a coarse porous material.