bluuebunny/crossref_metadata_2025 huggingface dataset:
WATIN—A COMPUTER PROGRAM FOR GENERATING INPUT FILES FOR WATEQF
Authors: Moses Carl O. , Herman Janet S.
Published: March 2006

Abstract. WATIN is a FORTRAN 77 program for creating and modifying input files of analytical data for WATEQF, the aqueous geochemical speciation/saturation model. WATIN uses menus to display information about the data file and to accept new information from the user. In addition to providing basic editing functions, WATIN provides default values for WATEQF parameters and checks for errors and inconsistencies in the data file. WATIN simplifies and streamlines access to WATEQF for both researchers and students, and along with WATEQF, can be an important part of a geochemical data analysis system.
A MICROCOMPUTER PACKAGE FOR DETERMINING OPTIMAL WELL DISCHARGE
Authors: Paudyal G. N. , Gupta A. Das
Published: March 2006

Abstract. A fully interactive microcomputer package consisting of two BASIC programs, OPTP and PTEST, is presented for determining the optimal well discharge. Program PTEST computes the coefficients and exponent of the nonlinear drawdown equation using three‐step data from a step‐drawdown pumping test. Program OPTP computes the optimal discharge using a single‐variable constrained nonlinear programming algorithm. The package, originally written for an IBM‐PC, can be adapted to any microcomputer with minor modifications.
Changes of Ground‐Water Quality Near a Well Undergoing Acid Treatment
Authors: Wojcik Wlodzimierz , Wieczysty Artur
Published: March 2006

One of the rehabilitation methods applied to wells incrusted with iron is acid treatment. In many cases, however, the owners of the wells and contractors are concerned about possible aquifer pollution. The aim of field experiments has been to find out how far hydrochloric acid can migrate within the unconsolidated aquifer during well treatment, and what changes it causes in the quality of ground water.

Results indicate that the acid remains near the well where it reacts with clogging deposits. Twenty‐four hours after acidizing, no changes in ground‐water quality were observed in piezometers at greater distances than 5.0 m from the well. After flush pumping, the ground water reverted to its original quality.
Geophysical Mapping of a Buried Basalt/Sedimentary Interface, Eastern Sudan
Authors: Ali Hamid O.
Published: March 2006

The El‐Shawak area in eastern Sudan lies within a large synclinal basin known as the Gedaref Basin, composed principally of elastic sediments of the Nubian Sandstone Formation which are overlain by sheets of basalt and dolerite and underlain by a metamorphic Basement Complex.

As a part of a hydrogeological research project in the area, gravity and seismic refraction techniques were combined to locate the extent of the basaltic flow and to determine the thicknesses of the sedimentary formations.

The results of these studies show that the topography of the Basement Complex is undulating and characterized by two troughs separated by subsurface ridges. The thicknesses of the Nubian Formation sediments range from 50 m (164 ft) to greater than 250 m (820 ft). Although the thicknesses of the Nubian Formation are favorable for ground‐water occurrence, the yield is very limited because the sediment succession is composed largely of compact mudstone.

The application of the gravity method in the El‐Shawak area has shown that a polynomial trend‐surface fit can be used to separate the regional and the residual components to reflect local geological features.
Airborne Geophysical Exploration for Ground Water
Authors: Paterson Norman R. , Bosschart Robbert A.
Published: March 2006

Geophysical methods have been used for many years to assist in hydrogeological exploration for ground water. For the direct detection of water‐bearing formations, the electrical resistivity method has been effective but relatively slow and costly.

More recently, surveys have been conducted successfully with electromagnetic prospecting apparatus developed primarily for the mineral industry. Such equipment has the advantages of greater speed and portability, improved subsurface resolution, and better potential discrimination of conductive aquifers.

Electromagnetic methods also can be applied from moving platforms, including fixed‐wing aircraft and helicopters. Detailed and regional surveys conducted in recent years for geological mapping and mineral exploration in Africa and elsewhere have revealed important information on the location and nature of water‐bearing formations and structures. Simultaneous measurements of the magnetic field have been used also to map faults and dikes of potential ground‐water significance.

New, wide‐band, digital airborne equipment and processing systems are capable of carrying out rapid, inexpensive studies of subsurface formations to depths of at least 200 meters. Computerized interpretation techniques can produce maps of depth and electrical conductance of a variety of buried aquifers. This information can be of direct assistance to the hydrogeologist or hydrologist in the identification and development of underground‐water supplies.
Generation of Ground‐Water Age Distributions
Authors: Campana Michael E.
Published: March 2006

Discrete‐state compartment (DSC) models and their associated age distribution functions permit the quantitative interpretation of environmental radioisotope data such as carbon‐14 ground‐water decay ages. These mixing‐cell models offer a means for constructing ground‐water flow models that can be used to relate decay ages to ground‐water mean ages. In addition, DSC models can also generate the entire distribution of ages in various subregions of a ground‐water reservoir. A preexisting DSC model of a portion of the Tucson Basin alluvial aquifer is used as an example. Ground‐water mean ages in this aquifer range from 100 to almost 15,000 years old, with the oldest waters about 40,000 years old. Since the ground‐water ages are not normally distributed, means and medians are not equivalent. The results indicate that care must be used in interpreting both ground‐water radioisotope decay ages as well as mean ground‐water ages and that knowledge of the entire age distribution is preferable. Age distributions are especially useful in hydrogeologic studies in which mixing is important and may find use in paleohydrogeologic investigations.
Radon and Radium Emanations from Fractured Crystalline Rocks – A Conceptual Hydrogeological Model
Authors: LeGrand Harry E.
Published: March 2006

Subsurface air is a refuge for radon gas escaping from rock and soil surfaces, as well as from subsurface water. Where the subsurface air is confined in a zone by overlying poorly permeable material or by downward‐moving water, the radon can accrete and become mobile. The crystalline rocks of eastern United States contain granites and associated rocks that have moderate to low amounts of uranium source material; the amounts are sufficient for radon to emanate significantly from both the soil‐saprolite zone and the part of the underlying fractured rock above the water table.

Both the soil‐saprolite confined air system and the fracture air system are nondescript and are erratic in size and shape from place to place and from time to time. They tend to have a gross horizontality because of blanket infiltration of precipitation and in some cases by crude layering of soil horizons or tension fracturing of bedrock.

The pressure increases in the air systems chiefly as infiltrated water moves downward and as the water table rises. The radon‐laden air moves toward two types of low‐pressure chambers. One type of chamber is a house on sloping topography niched into the soil‐saprolite zone and perhaps into bedrock fractures. The other type is the unwatered fracture zone of a pumping cone of depression where overlying clays are less permeable. These two types of low‐pressure chambers have characteristics of vacuum cleaners, sucking in radon‐laden air.

Conditions leading to high indoor radon concentrations are: (1) granites and associated rocks with normal or above normal amounts of uranium, (2) normal interconnecting fracture pattern, (3) a thin mantle of relatively impermeable clay soil, (4) repeated cycles of recharge and of a fluctuating water table in the fracture zone or in the overlying regolith, (5) indentation of buildings into soil and rock materials, and (6) building construction allowing relatively easy inflow of air from the subsoil and rock.
Hydraulic/Chemical Changes During Ground‐Water Recharge by Injectiona
Authors: Hamlin Scott N.
Published: March 2006

Ground‐water recharge by injection of reclaimed water is a feasible method of improving ground‐water quality in the shallow aquifer system in the Palo Alto Baylands along the San Francisco Bay. Ground water was initially more saline than sea water. Reclaimed water was injected at a rate of 10 gallons per minute from June 5, 1980, to July 1, 1980. At the completion of injection, water from an observation well 31 feet from the injection well was 98 percent injected water‐in essence, fresh water.

An abrupt rise in the water level in the injection well of about 1.5 feet during the initial injection test was the result of a 3.5 percent density difference between injected fresh water and saline ground water. The arrival of injected water at observation wells showed the same effect, allowing monitoring of chemical and hydraulic changes entirely through water‐level data.

The initially sodic clays in the confining layer were expected to swell as the saline ground water (sodium source) was diluted by recharge water. The sodium ion causes excessive coordination with the hydronium ion (H3O+) in the clay lattice, resulting in expansion as the saline water is diluted. X‐ray diffraction analysis of clay samples soaked first in native and then in injected water showed this effect. Calcium replaces sodium and limits expansion.

Prior to injection the saline ground water was supersaturated with calcite. Dilution, as injection proceeded, eventually produced an undersaturation of calcite. An increase in well specific capacity indicates that calcite dissolved from the aquifer matrix, improving hydraulic conductivity.
The Impact of the Dupuit‐Forchheimer Approximation on Salt‐Water Intrusion Simulation
Authors: Kemblowski Marian
Published: March 2006

Numerical analysis based on the finite‐difference and boundary element methods is used to investigate the impact of the Dupuit‐Forchheimer approximation on results of salt‐water intrusion simulation. It is found that for sinks or sources (drain, ditch) that are small compared to the freshwater‐zone thickness, the use of the Dupuit‐Forchheimer approximation may cause substantial errors. For such cases, a correction method is proposed and verified.
VOCs in Ground Water Influenced by Large Scale Withdrawals
Authors: Fischer Alex J. , Rowan Elizabeth A. , Spalding Roy F.
Published: March 2006

Ten wells were installed to monitor the water‐table elevation and volatile organic compounds (VOCs) in ground water underlying Hastings, Nebraska. Trichloroethylene (TCE) was the most frequently detected VOC and had the highest concentration (1750 μg/1) in these monitoring wells. Perchloroethylene (PCE), 1,1‐dichloroethylcne (1,1‐DCE), 1,2‐dichloroethane (1,2‐DCA), and 1,1,1‐trichloroethane (TCA) also occurred in one or more of the monitoring wells. The vertical and areal VOC distribution in both the contaminated monitoring wells and the city's contaminated municipal wells are largely related to withdrawal caused by heavily pumped, nearby municipal and industrial wells. A computer model was used to demonstrate the impact historic site changes in high capacity well withdrawal have on the local water‐table configuration. Two sites of suspected VOC sources are designated for further investigation
Monitoring Well Installation, Purging, and Sampling Techniques — Part 2: Case Histories
Authors: Keely Joseph F. , Boateng Kwasi
Published: March 2006

Three case histories are presented to illustrate the problems encountered using some monitoring well installation, purging, and sampling techniques. Hollow‐stem auger‐ing was found to pose problems during the installation of monitoring wells in terms of potential for cross‐contamination of strata, the inability to emplace an adequate filter pack, the potential for smearing natural clays into sand and gravel strata, and the possible need for excessive purging of sediments that accumulate between sampling events. Cable tool drilling was found to allow construction of high quality wells, but was slow and expensive. Concern over the potential for increased emissions of noxious vapors from the borehole when drilling with the air rotary method prevented its use in situations where highly contaminated strata were likely to be encountered. A hybrid drilling technique, augering with temporary casing, was able to provide the advantages, and minimize the disadvantages, of the foregoing drilling methods.

The installation of vertically separated clusters of monitoring wells lent important insights into the potential movement of a contaminant plume. Detailed aquifer tests provided needed information on the hydraulic behavior of the subsurface strata occupied by the plume so that potential pathways of contaminant transport could be more accurately identified. Obtaining reliable data from such tests depended greatly on the ability of each monitoring well to act as a high quality hydraulic observation well. The selection of drilling and installation techniques that ensured minimal disturbance of the near‐borehole environment provided the best guarantee of such performance.
Analysis of Hydraulic Gradients Across the Host Rock at the Proposed Texas Panhandle Nuclear‐Waste Repository Site
Authors: Bair E. Scott
Published: March 2006

Analysis of the direction of ground‐water flow across the host rock at the proposed high‐level nuclear‐waste repository site in Deaf Smith County, Texas, is complicated by vertical and lateral changes in the density of formation fluids in the various hydrogeologic units that overlie and underlie the proposed host rock. Because the concept of hydraulic head is not valid when evaluating vertical hydraulic gradients in a variable‐density flow system, other methods were used to determine the direction and magnitude of vertical hydraulic gradients at the proposed site where the specific gravity of formation fluids varies between 1.00 and 1.28. The direction of ground‐water flow across the proposed host rock, an 80‐foot‐thick salt bed in the Lower San Andres Formation, was determined by calculating vertical hydraulic gradients based on formation pressure and fluid density data, and by analysis of pressure‐depth diagrams. Based on data from the vicinity of the proposed site, both methods indicate the potential for downflow across the host rock. Downflow or predominantly horizontal flow is considered a favorable prewaste emplacement condition because it prolongs the‐travel time to the biosphere of any naturally or accidentally released radionuclides.
Hydrogeologic Characteristics of the Ramapo Fault, Northern New Jersey
Authors: Ganser Donald R.
Published: March 2006

The Ramapo Fault is a major structural feature of northern New Jersey separating the Triassic‐age Newark Basin from the Precambrian Reading Prong. When the New Jersey Department of Transportation proposed extending Interstate Highway 287 north of Boonton, New Jersey, along the fault alignment, concerns were raised regarding the potential for the fault to act as a preferential source of ground‐water recharge to aquifers supplying domestic and industrial needs. It was feared that highway contaminants and spills could infiltrate the fault zone, be transported along the fault, and recharge the unconsolidated Pleistocene‐age buried valley aquifers, principally the Towaco Valley aquifer.

As a result of these concerns, a detailed investigation was performed to determine the location and hydrogeologic character of the fault. Geologic mapping and geophysical techniques were employed to locate the fault prior to core drilling and packer testing of the fault. Geophysical logs were obtained from the borings to assist in characterization of the formation properties and to verify the fault location.

The results of the investigation indicate that the Ramapo Fault has a calculated hydraulic conductivity of less than 1 × 10−7 cm/sec which was indistinguishable from the surrounding formations. It was concluded that the Ramapo Fault does not provide ground‐water recharge to the unconsolidated buried valley aquifers within the study area. The deltaic deposits overlying bedrock directly up‐gradient of the buried valley exhibited relatively high hydraulic conductivity (10−2 cm/sec) providing the major source of recharge to the unconsolidated aquifers in the Towaco Valley.
Applications of Universal Kriging to an Aquifer Study in New Jersey
Authors: Pucci Amleto A. , Murashige Jo Ann E.
Published: March 2006

This article describes the use of kriging for optimizing data collection and utility in a regional ground‐water investigation of the Potomac‐Raritan‐Magothy aquifer system in central New Jersey. Kriging was used to (1) estimate the altitude of an aquifer surface, (2) estimate hydraulic conductivities from point data, and (3) estimate the associated kriged errors. The selection of locations for additional data collection, based on the kriged errors, was effective in terms of improving the aquifer surface data base. In another application, hydraulic conductivity values were kriged, first using equal weights, then unequal weights to account for the reliability of the data. The weighting values that were used for unequal weighting were estimated by an analysis of variance. Although inclusion of the data reliability in the kriging will increase the kriged errors, the accuracy of the range of uncertainty in the interpolated values also increases.
DBCP, EDB, and TCP Contamination of Ground Water in Hawaii
Authors: Oki Delwyn S. , Giambelluca Thomas W.
Published: March 2006

In recent years, several pesticide‐related contaminants have been detected in the ground waters of the State of Hawaii. Two soil fumigants previously used by pineapple growers, 1,2‐dibromo‐3‐chloropropanc (DBCP) and 1,2‐dibromoethane or ethylene dibromide (EDB), have been detected in several wells on Oahu and Maui. An impurity of the soil fumigant DD, 1,2,3‐trichloropropane (TCP), also has been detected in a number of wells. DBCP, EDB, and TCP are of particular concern to State public health officials due to known and possible unknown health effects associated with these compounds.

The locations of the contaminated well sites on Oahu appear to be correlated with the areas of past and present pineapple cultivation when the ambient ground‐water flow pattern is taken into consideration. In addition, several large fuel pipeline leaks are located in the vicinity of the EDB contamination. In general, TCP contamination is more widespread than either DBCP or EDB contamination. TCP levels appear to be declining in Oahu water wells while EDB levels in the contaminated portion of southern Oahu appear to be increasing. The direction of temporal trends in DBCP concentration at present varies according to site.
Seepage Face Simulation Using PLASM
Authors: Potter Scott T. , Gburek William J.
Published: March 2006

An unconfined aquifer variation of the Prickett and Lonnquist Aquifer Simulation Model (PLASM) has been modified to simulate the dynamics of seepage face development and compute flow rates therefrom. The modifications, based on hydraulic theory and operating within the framework of the original model, enable the model to simulate zones of seepage contiguous and noncontiguous to streams, lakes, or other points of ground‐water discharge. A simplistic overland flow routing procedure to move seepage flow downslope from points of discharge and permitting it to reenter where the water table is below the land surface was also incorporated.

To determine the error associated with this discrete solution, the modified numerical model was compared to a series of analytically equivalent Dupuit‐Forchheimer‐based solutions. The numerical solutions from PLASM compare to the closed‐form solutions to within the uncertainty of the model's finite‐difference discretization. The comparisons indicate that errors in seepage face prediction result strictly from PLASM's inclusion of the D‐F approximations, not from the formulation of the numerical seepage face simulation routine. Finally, the modified PLASM was applied to a hypothetical watershed under dynamic conditions to demonstrate its capabilities.

The unconfined aquifer version of PLASM works best in situations where both thickness‐to‐length ratio of the aquifer and land surface and water‐table slopes are relatively small, geometry typical of many real‐world watersheds. Under such conditions, the modifications developed are shown to logically and consistently simulate the extent, dynamics, and flow rates of seepage zones with minimum error.
A Horizontal Plane Source Model for Ground‐Water Transport
Authors: Galya Donald P.
Published: March 2006

A model was derived through the use of Green's functions to simulate three‐dimensional contaminant transport from a horizontal plane source (HPS). This analytical model incorporates retardation and decay, and can simulate varying source emission rates. Appropriate uses of the model include simulations of contaminant transport from landfills, waste lagoons, land treatment facilities, and areas of pesticide application. Comparison between HPS and point source solutions indicates that for such simulations, the HPS model will provide more accurate results than the point source solution, particularly near the source. Representative model applications indicate the model's sensitivity to variations in retardation, decay, and temporal period of source emission.
A Computer Model for Simulating Water Quality and Quantity in a Wellfield in an Alluvial Aquifer
Authors: Gilliland Martha W. , Nguyen Quang M.
Published: March 2006

A surface‐water/ground‐water interaction computer model was developed for the Grand Island, Nebraska municipal wellfield. This finite‐difference model, which is two‐dimensional in plan view, includes both quantity and quality components. The quantity component is a modified version of the Prickett‐Lonnquist model. Modifications account for the effects of the Plattc River channels, which flow through the modeled area, and adjust water levels at pumping wells to account for the difference between the well radius and the grid size. The quality component of the model calculates nitrate concentrations in pumping wells penetrating aquifers which arc vertically stratified with respect to nitrate. The model also estimates amounts of recharge from the river to the aquifer and the direction and velocity of movement of ground water in several nitrate‐contaminated areas adjacent to the wellfield. Nitrate is assumed to be a conservative pollutant, and nitrate transport is assumed to be solely due to advection. The model was calibrated using field data collected in 1984 and then verified with field data from two other independent events in 1978 and 1984. After calibration, the difference between measured and simulated heads at individual wells was less than one foot. Predicted nitrate concentrations in the pumping wells ranged from 0.07 to 0.40 mg/1 NO3‐N which is within the measured range of 0.00 to 0.58 mg/1 NO3‐N. River recharge predictions ranged from 176 to 200 cfs, whereas measured values were 168 to 232 cfs. The model was used to investigate the impacts of river diversions upstream on the quantity and quality of water in the wellfield. Simulation results indicate that zero‐flow conditions in the river cause drawdown to increase greatly, cause the nitrate concentration in the pumping wells to increase slightly, and cause the ground water in the nitrate‐contaminated area north of the wellfield to begin moving toward the wellfield.
Statistical Methods for Characterizing Ground‐Water Quality
Authors: Harris Jane , Loftis Jim C. , Montgomery Robert H.
Published: March 2006

The benefits from ground‐water quality monitoring ultimately depend on the statistical methods used to analyze data. The methods must match both the information expectations of users and the characteristics of the water quality variables to which they are applied. The primary objective of regulatory ground‐water monitoring is detecting changes in quality. To select appropriate statistical tests for change, one must know whether the water quality variables of concern are seasonal, normally distributed, and serially dependent. This paper provides guidance in analyzing limited background data sets to determine these three characteristics.

Recommended procedures to detect seasonality were pcriodograms, Student's t‐test, Mann‐Whitney test, analysis of variance, and Kruskal‐Wallis test. To test for normality, the skewness coefficient is recommended. To detect serial dependence, sample autocorrelation coefficients may be tested for significance.
A MICROCOMPUTER PROGRAM FOR INTERPRETING TIME‐LAG PERMEABILITY TESTS
Authors: Thompson Debora B.
Published: March 2006

Abstract. Single‐well tests based on the rate of water‐level recovery after raising or lowering the water level in a well have long been used as a quirk and simple method of obtaining order‐of‐magnitude estimates of hydraulic conductivity. The BASICS program presented allows for the rapid interpretation of these tests for most field situations.
The Politics of Ground‐Water Management Reform in Oklahomaa
Authors: Roberts Rebecca S. , Gros Sally L.
Published: March 2006

This paper examines the politics of ground‐water management reform in Oklahoma. It argues that the geographic distribution of water supplies and uses significantly modifies the distribution of costs and benefits of reform among political constituencies. Effective restrictions on ground‐water withdrawals would raise large and immediate threats to irrigators and farm communities dependent on irrigation in western Oklahoma. Municipal and industrial water users, concentrated in eastern Oklahoma and reliant on more plentiful surface‐water supplies, would receive more diffuse, longer‐range benefits to management reform. These effects have significant implications for the politics of ground‐water management. The results of the analysis suggest that approaches taken to ground‐water management reform in Oklahoma, and the other eastern Ogallala states, may be more effective and realistic than might initially be thought.

Oklahoma's present ground‐water law, adopted in 1973, is based on a utilization policy of planned depletion and represents a major change in direction entailing significant implementation costs. Agricultural interests, seeking to protect their irrigation rights, were influential in both the adoption and implementation processes. Considering the problems encountered, the immediate outlook for effective state management of ground water remains unfavorable. Future prospects, however, are more favorable. Oklahoma has developed an institutional structure capable of responding to changing priorities and needs of irrigators. This long‐run approach to ground‐water management matches the interests of the most relevant political constituency and may prove to be the most effective strategy.
Water Movement in Till of East‐Central South Dakota
Authors: Cravens Stuart J. , Ruedisili Lon C.
Published: March 2006

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

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

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

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

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

In a hazardous waste disposal facility located in a saturated soil, the local water table and the capillary fringe zone are modified by the presence of the facility. In this paper, a conformal mapping solution to the accompanying ground‐water flow is presented. The solution allows one to display, in the two‐dimensional approximation, the flow net around an excavation in terms of the capillarity, local geometry, and flow properties.

Capillarity can significantly influence net flow into an excavation; typical values can cause net flow to be 10 to 20 percent higher than predicted without capillarity.

Anisotropic behavior also can be important. It is shown that anisotropy favoring horizontal flow can greatly alter the flow net and the total flow.
An Analytical Solution to Saturated Flow in a Finite Stratified Aquifera
Authors: Yates S. R.
Published: March 2006

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

Water‐resources investigations concerned with contaminant transport through aquifers comprised of very loose, unconsolidated sediments have shown that small‐scale variations in aquifer characteristics can significantly affect solute transport and dispersion. Various sampling and borehole‐logging techniques have been integrated into these studies to detect and measure detailed formation changes through casing or well screen along the length of the borehole. Commonly, measurement accuracy and resolution have been limited by a borehole environment consisting of an annulus of disturbed sediments produced by the casing‐installation method.

In an attempt to quantify this disturbance and recognize its impact on the characterization of unconsolidated deposits, three installation methods were examined and compared in a sand‐and‐gravel outwash at a test site on Cape Cod, Massachusetts. These installation methods were: (1) casing installed in a mud‐rotary hole; (2) casing installed in an augered hole; and (3) flush‐joint steel casing hammer‐driven from land surface. Fifteen wells were logged with epithermal neutron and natural gamma tools. Statistical analyses of these digitized nuclear logs proceeded under the fundamental hypothesis that a large variance indicated preservation of layering in the surrounding sediments, significant variability at a small scale, and a small level of disturbance. Conversely, a small variance corresponded to mixing, poor detail, and larger disturbance. The statistical information generated from a systematic “analysis of variance” investigation confirmed an intuitive assessment of the problem by demonstrating that, under the conditions encountered at this site, augering is the most disruptive of the three casing‐installation methods and that driving casing directly, though typically a more time‐consuming operation, transmits the least amount of disturbance into the surrounding formation.
Hydrochemical Characterization of Brines and Identification of Brine Contamination in Aquifersa
Authors: Novak Stephanie A. , Eckstein Yoram
Published: March 2006

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

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

Abstract. A sampling manifold has been developed that allows the rapid collection of ground water from multilevel samplers during tracer tests. Its reliability was proven in an experiment lasting 51 days.
Recharge from a River of Large Width to a Shallow Water‐Table Aquifer
Authors: Mishra G. C. , Seth S. M.
Published: March 2006

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

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

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

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

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

A semianalytical particle tracking method was developed for use with velocities generated from block centered finite‐difference ground‐water flow models. The method is based on the assumption that each directional velocity component varies linearly within a grid cell in its own coordinate directions. This assumption allows an analytical expression to be obtained describing the flow path within an individual grid cell. Given the initial position of a particle anywhere in a cell, the coordinates of any other point along its path line within the cell, and the time of travel between them, can be computed directly. For steady‐state systems, the exit point for a particle entering a cell at any arbitrary location can be computed in a single step. By following the particle as it moves from cell to cell, this method can be used to trace the path of a particle through any multidimensional flow field generated from a block‐centered finite‐difference flow model.