bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Horizontal Aquifer Anisotropy with Three Wells
Authors: Neuman Shlomo P. , Walter Gary R. , Bentley Harold W. , Ward John J. , Gonzalez Don Diego
Published: March 2006

Existing methods for the determination of horizontal aquifer anisotropy by means of pumping tests require a minimum of four wells, one for water withdrawal and three for drawdown observations. This paper shows how the same methods can be used to determine anisotropy with as few as three wells, if at least two of them can be pumped in sequence. A field example is included. A method of analyzing data from more wells than the above minimum, by least squares, is also described.
Microcomputer Model of Artificial Recharge Using Glover's Solution
Authors: Molden D. , Sunada D. K. , Warner J. W.
Published: March 2006

An interactive program written for an APPLE II+ 48K computer is presented which solves Glover's (1960) analytical solution for recharge from a rectangular basin. The program is capable of graphically displaying the rise and decline of the recharge mound for either an infinite homogeneous medium or for a stream aquifer system.
Relationships Between Ground‐Water Silica, Total Dissolved Solids, and Specific Electrical Conductivity
Authors: Day Barbara A. , Nightingale Harry I.
Published: March 2006

Specific electrical conductivity (SEC), total dissolved solids (TDS), and silica (SiO2) are ground‐water quality parameters routinely measured in a laboratory. Electrical conductivity measurements are made quickly and are less costly than TDS measurements. Once the relationship between the parameters is determined by regression analysis, TDS can be estimated quickly from the SEC and SiO2 measurements. Water quality data from 25 city wells in Fresno, California, and historical ground‐water quality data from the adjacent San Joaquin River/Kings River alluvial interfan (central San Joaquin Valley, California), the Kaweah River alluvial fan, and the Kern River alluvial fan (southern San Joaquin Valley) were used in this investigation. For the specific hydrologic areas studied, the model's TDS predictive ability is improved when SiO2 is included with SEC as the independent variables.
Comparison of Aquifer Characteristics Derived from Local and Regional Aquifer Testsa
Authors: Randolph R. B. , Krause R. E. , Maslia M. L.
Published: March 2006

A comparison of the aquifer parameter values obtained through the analysis of a local and a regional aquifer test involving the same area in southeast Georgia is made in order to evaluate the validity of extrapolating local aquifer‐test results for use in large‐scale flow simulations. The case study involves an increase in pumpage of 6.3 Mgal/d (million gallons per day) for the local test and a reduction in pumpage of 66 Mgal/d for the regional test, each involving the same well field. The test involved the Floridan aquifer system, a limestone sequence characterized predominantly by secondary permeability in this area. Time‐drawdown and time‐recovery data were analyzed by using both graphical and least‐squares fitting of the data to the Theis curve. Additionally, directional transmissivity, transmissivity tensor, and angle of anisotropy were computed for both tests. The major and minor axes of the transmissivity ellipse determined from the regional test show general agreement with those determined from the local test. A slightly higher ratio of anisotropy was observed on the regional scale: 2.1:1, than on the local scale: 1.5:1. Regional storage coefficients ranged from 3.4 × 10−4 to 7.2 × 10−4 as compared with local storage coefficients ranging from 1.8 × 10−4to 5.3 × 10−4.
Simulation of Ground‐Water Flow in Southeastern Oahu, Hawaii
Authors: Eyre Paul Richard
Published: March 2006

On the leeward side of southeastern Oahu, Hawaii, near‐vertical dikes have intruded the gently dipping and highly permeable lava flows of the Koolau mountain. These dikes bound the study area on the north and west and internally divide it into the Waialae and Wailupe‐Hawaii Kai aquifers. Recharge to these aquifers, 6 and 9 million gallons per day respectively, has created Ghyben‐Herzberg lenses that freely float on sea water and discharge to the sea through coastal sediments. In the Waialae area, where rainfall is high and where thick (poorly permeable) coastal sediments inhibit the discharge of fresh water, heads are 8 to 15 feet above sea level. Lower rainfall and thin coastal sediments that allow easy discharge cause heads to be only 1 to 5 feet in the Wailupe‐Hawaii Kai area.

The flow of ground water and the effects of future water development were simulated using AQUIFEM, a two‐dimensional finite‐element flow model, modified for aquifers containing a sea‐water interface. The model provides accurate simulation of observed heads averaged over several years and predicts an additional area‐wide head decline of about 1 foot when three recently drilled wells are put into production.
Rejection of Recharge Water from Madison Aquifer Along Eastern Perimeter of Bighorn Artesian Basin, Wyoming
Authors: Huntoon Peter W.
Published: March 2006

Approximately half of the perimeters of Wyoming foreland artesian basins are characterized by structural continuity of the Paleozoic aquifers between the recharge areas and the interior parts of the artesian basins. A significant percentage of the ground water which circulates through such recharge areas is rejected through springs because there is a marked decrease in transmissivity basin‐ward from the recharge areas. The transmissivity contrasts have developed since the recharge areas became morphologically differentiated from the basin interiors during post‐Laramide time. Secondary enhancement of permeabilities is occurring in the recharge areas through dissolution of the rock matrix and cement, and in some locations the rocks were tectonically fractured. In contrast, the rates of dissolution within the basin interiors are substantially decreased, or processes of recrystallization, cementation, or compaction are operating to destroy permeability. The result is that in the case treated here, net recharge to the basin interior is a small fraction of measured stream losses in the headwaters of the recharge area.
Distribution of Volatile Organic Compounds in a New Jersey Coastal Plain Aquifer System
Authors: Fusillo Thomas V. , Hochreiter Joseph J. , Lord Deborah Grant
Published: March 2006

Samples for analysis of volatile organic compounds were collected from 315 wells in the Potomac‐Raritan‐Magothy aquifer system in southwestern New Jersey and a small adjacent area in Pennsylvania during 1980–82. Volatile organic compounds were detected in all three aquifer units of the Potomac‐Raritan‐Magothy aquifer system in the study area. Most of the contamination appears to be confined to the outcrop area at present. Low levels of contamination, however, were found downdip of the outcrop area in the upper and middle aquifers.

Trichloroethylene, tetrachloroethylene, and benzene were the most frequently detected compounds. Differences in the areal distributions of light chlorinated hydrocarbons, such as trichloroethylene, and aromatic hydrocarbons, such as benzene, were noted and are probably due to differences in the uses of the compounds and the distribution patterns of potential contamination sources.

The distribution patterns of volatile organic compounds differed greatly among the three aquifer units. The upper aquifer, which crops out mostly in less‐developed areas, had the lowest percentage of wells with volatile organic compounds detected (10 percent of wells sampled). The concentrations in most wells in the upper aquifer which had detectable levels were less than 10 /μg/1. In the middle aquifer, which crops out beneath much of the urban and industrial area adjacent to the Delaware River, detectable levels of volatile organic compounds were found in 22 percent of wells sampled, and several wells contained concentrations above 100 μ/1. The lower aquifer, which is confined beneath much of the outcrop area of the aquifer system, had the highest percentage of wells (28 percent) with detectable levels. This is probably due to (1) vertical leakage of contamination from the middle aquifer, and (2) the high percentage of wells tapping the lower aquifer in the most heavily developed areas of the outcrop.
Interference Due to Neighboring Wells During Pumping Tests
Authors: Rushton K. R.
Published: March 2006

When other wells are pumping from an aquifer in which a pumping test is being carried out, they can interfere with the observed data. Even if the interfering wells are several kilometers away, they can have a significant effect on test results. The effect of the interfering wells on the drawdown can be misinterpreted .as boundary effects. By combining the series expansions for the Theis expression for the pumped and interfering wells, it is shown that the magnitude of the interference depends primarily on the length of time for which the interfering well pumps before the start of the test. An important finding of the analysis is that the distance between the test and interfering wells has a small effect. A method of correcting for the effect of an interfering well during both pumping and recovery phases is introduced.
LUMPED PARAMETER MODEL: FURTHER APPLICATION IISI CHALK AQUIFERS, U.K.
Authors: Walsh D. M. , Puri S.
Published: March 2006

Abstract. Keating (1982) used a lumped parameter model to explain an unusual chalk aquifer consisting of a thin zone of high storage and transmissivity whose response of small annual fluctuations and high stream flows were considered to be anomalous. A similar model has been further developed and used in a preliminary desk study of possible river augmentation schemes. The model developments incorporate stream bed leakage to the aquifer and saturated depth varying transmissivity. As a result the model is versatile in its ability to test a variety of control rules for ground‐water abstraction. The newly incorporated factors are significant for assessment of the degree of success of augmentation proposals. This lumped model gave valuable guidance for future field investigations.
Estimating Vertical Soil Moisture Flux at a Land Treatment Site
Authors: Dreiss S. J. , Anderson L. D.
Published: March 2006

Estimation of rates of contaminant movement at land treatment sites requires accurate measurements of water movement through the soil zone. A moisture balance method that employs the zero flux plane concept and several simplifying assumptions about saturated and unsaturated flow conditions gives reasonable estimates of evapotranspiration and percolation fluxes when applied to a land treatment site in central coastal California. The technique requires measurements of the saturated hydraulic conductivity of field soils as well as soil matric suction and moisture content at regular time intervals. Replicate monitoring clusters for matrix suction and moisture content are necessary in spatially variable soils but a detailed knowledge of the spatial variability of saturated hydraulic conductivity is not warranted.
Simulated Salt‐Water Movement in the Nakhon Luang Aquifer, Bangkok, Thailand
Authors: Gupta A. Das
Published: March 2006

Analytical and numerical modeling procedures based on the hydrodynamic dispersion were used to analyze the salt‐water contamination problem in the Nakhon Luang aquifer underlying the City of Bangkok. A preliminary evaluation is performed for the approximate locations of the contaminating sources, and its rate and pattern of encroachment are predicted under different operating conditions in the future to assist in planning an efficient and economic monitoring network. The contaminating source is widespread and is located on the western side of the Chao Phraya River. With the present trend of pumping, the rate of encroachment is greatest from the northwest direction towards the main pumping center. The study indicates the advantage of performing one‐dimensional model analysis prior to attempting two‐dimensional regional analysis, particularly in cases where the initial chloride concentration distribution is unknown.
Septic Tank Density and Ground‐Water Contamination
Authors: Yates Marylynn V.
Published: March 2006

As more and more cases of ground‐water contamination are reported, the public has become increasingly aware of the importance of preserving the quality of this limited resource, especially in areas totally dependent on ground‐water sources. Although most of the attention is focused on pollution by organic chemicals, these compounds are responsible for a relatively small percentage of ground‐water‐related disease outbreaks. The majority of waterborne disease outbreaks are caused by bacteria and viruses present in domestic sewage. Septic tanks contribute the largest volume of waste water, 800 billion gallons per year to the subsurface, and are the most frequently reported cause of ground‐water contamination associated with disease outbreaks. The U.S. Environmental Protection Agency has designated areas with septic tank densities of greater than 40 systems per mi2 (1 system per 16 acres) as regions of potential ground‐water contamination. Numerous cases of ground‐water contamination have been reported in areas of high septic tank density; lot sizes in these areas range from less than one‐quarter acre to three acres. The single most important means of limiting ground‐water contamination by septic tanks is to restrict the density of these systems in an area.
Use of Rain and Dry Deposition Compositions for Interpreting Ground‐Water Chemistry
Authors: Wagner George H. , Steele Kenneth F.
Published: March 2006

Waters from 91 springs in a 130 X 140 km area of west‐central Arkansas were analyzed for all the major ions. The yearly flux of these ions in the rain and pure‐water extract of the dry deposition 180 km north of this area was measured and assumed to represent the composition of the recharge to the ground water feeding the springs. Cation/Cl‐flux ratios were used as a norm for the concentration of ions in the spring waters by evapotranspiration. Ratios above the norm were interpreted as ion exchange or rock dissolution into the ground waters. Ratios below the norm were interpreted as ion adsorption or, for Ca2+, CaCO3 precipitation processes. Na+ and Mg2+ are invariably above the norm. K+, NH+4 and H+ are invariably below the norm; whereas Ca2+ values are about equally divided between above and below the norm. Equivalents of cations above the norm and below the norm were compared for a number of springs to determine the main ground‐water processes for each spring. The Na+/Cl‐ and K+/Cl‐ norms for the rain water form near‐perfect minimum and maximum envelopes, respectively, of the Na+ vs Cl‐ plots of the spring‐water compositions. This is due to the adsorption affinities of the soil for Na+ being low, and for K+ being high.
Relationship of Geology, Physiography, Agricultural Land Use, and Ground‐Water Quality in Southwest Georgiaa
Authors: Beck Barry F. , Asmussen Loris , Leonard Ralph
Published: March 2006

Water samples were collected from 34 wells in the Claiborne aquifer in southwest Georgia. Land use/cover is principally forest, wetland, or agriculture. The aquifer is exposed surficially to the northwest but dips beneath confining beds to the southeast. The Claiborne aquifer is generally a fine‐ to medium‐grained quartz sand becoming more calcareous downdip and to the east. Well water was analyzed in the field for pH, electrical conductivity, alkalinity, hardness, and temperature, and in the laboratory for Cl, NH4, NO3, total N, total P, ortho‐P, SO4, K, Na, Ca, Mg, and Fe. Hardness gradually increases from 5 mg/1 updip to 162 mg/1 downdip and bicarbonate alkalinity follows the same trend reflecting variations in the aquifer lithology. Higher than normal nitrate concentrations (4‐6 mg/1) are found in ground water in the exposed updip portion of the aquifer in areas where agricultural land use for cropland is high. However, in forest‐covered areas, ground water in the exposed portion of the aquifer contains nitrate concentrations similar to the confined areas of the aquifer: less than 1 mg/1. Other chemical constituents measured do not show a discernible pattern of variation. One well near a fertilizer storage facility contains nitrate concentrations exceeding the Safe Drinking Water Standards, and other wells in the agricultural portion of the outcrop belt may seasonally exceed these limits.
The Use of Hydrogeochemical Patterns in Carbonate Sand and Sandstone Aquifers to Identify Intrusion and Flushing of Saline Water
Authors: Mercado Abraham
Published: March 2006

Chemical analyses of wells penetrating the coastal aquifer of Israel indicate that the relative concentrations of sodium, calcium, magnesium, bicarbonate, and hydrogen species deviate considerably from the ideal mixing line between fresh water and sea water, as represented by the concentration of chlorides. Furthermore, deviation patterns were found to be distinctly different for areas of present sea‐water intrusion, and areas from which ancient brines are still flushed. These differences, explainable in major part as the combined effects of cation exchange and carbonate equilibria, can in turn be utilized to distinguish between invading and retreating saline‐water bodies, and identify their existence at the very beginning of the salinization process. Observed patterns are verified here in major part, with the aid of a single‐cell simulation model.
Analysis of Flow to a Large‐Diameter Well During the Recovery Period
Authors: Mishra G. C. , Chachadi A. G.
Published: March 2006

Unsteady flow to a large‐diameter well in a confined aquifer during recovery has been analyzed by discrete kernel approach. A family of type curves has been presented for different durations of pumping. These type curves provide a fairly accurate means of determining aquifer parameters from data of pump tests conducted in a large‐diameter well. The replenishment of well storage at various times has been estimated.
Migration of Chlorophenolic Compounds at the Chemical Waste Disposal Site at Alkali Lake, Oregon – 2. Contaminant Distributions, Transport, and Retardation
Authors: Johnson Richard L. , Brillante Susan M. , Isabella Lome M. , Houck James E. , Pankow James F.
Published: March 2006

The behaviors of five chlorophenols and three chloro‐phenoxyphenols (CPPs) have been investigated at the chemical waste disposal site at Alkali Lake, Oregon. All of the compounds demonstrated similar trends in areal distribution hydraulically downgradient from the site. The transport distances for the di‐ and trichlorophenols were influenced greatly by their ionization in the high pH (˜10) ground water. In batch equilibrium experiments, these compounds were found to have Kp values of ˜0.0 for the soil and ground water taken from the site. While also largely ionized at pH ∼ 10, a tetrachlorophenol, pentachlorophenol, and the CPPs demonstrated substantial sorption in the batch equilibrium experiments as well as retardation relative to the di‐ and trichlorophenols at the site. The retardations observed relative to 2,6‐dichlorophenol were less than predicted based on the batch equilibrium results. Possible reasons include cosolvent effects due to the plume itself, nonuniform contaminant distributions at the time of the original burial, the fractures which are present in the aquifer, and a decreasing ground‐water velocity with distance westward of the site. Evidence is presented to support the last reason. These results show, for the first time, well‐behaved concentration contours embodying compound‐dependent retardation in the transport of sorbing and nonsorbing organic compounds from an existing waste disposal site.
A PROGRAM TO CALCULATE AQUIFER TRANSMISSIVITY FROM SPECIFIC‐CAPACITY DATA FOR PROGRAMMABLE CALCULATORS
Authors: Czarnecki John B. , Craig R. W.
Published: March 2006

. A program that will calculate aquifer transmissivity from the specific capacity of a well has been developed for handheld programmable calculators. The program extends the approach of Theis and others (1963) beyond the visual graphical interpolation of transmissivity values from type curves and solves directly a nonlinear equation for transmissivity, using a modified Regula Falsi solution algorithm. The program eliminates errors associated with visual interpolation of transmissivities obtained from type curves, especially for values of small transmissivities, and provides a quick and portable method of obtaining transmissivity values onsite.
Subdivision of Thick Sedimentary Units into Layers for Simulation of Ground‐Water Flowa
Authors: Weiss Jonathan S. , Williamson Alex K.
Published: March 2006

Subdividing thick sedimentary units into model layers based solely on stratigraphy can lead to serious violation of ground‐water flow modeling restraints and produce erroneous results. Borehole geophysical data can be used to suggest relative permeabilities and delineate model layers that are more likely to have uniform hydraulic properties than layers delineated by stratigraphic definitions alone. The uniformity within layers emphasizes the permeability contrast between layers, thereby allowing a quasi three‐dimensional approach.

Sedimentary units containing many thin beds of limited areal extent must be subdivided into model layers which incorporate large variations in hydraulic properties. The lack of permeability contrast between layers requires a fully three‐dimensional approach. In this case, the subdivision into layers needs to be made by including an evaluation of depths of producing zones, and the resultant vertical distribution of hydraulic heads. Nonlinear vertical hydraulic‐head gradients can occur in thick sedimentary units due to uneven vertical distribution of pumpage and small vertical permeabilities. Because these hydraulic‐head gradients are not modeled within a layer, the subdivisions should be made such that the model layers permit simulation of vertical hydraulic‐head gradients which can closely approximate observed gradients.

These methods are applied to the thick sedimentary units of the Gulf Coastal Plain, U.S.A.
Approximation of Salt‐Water Interface Fluctuation in an Unconfined Coastal Aquifer
Authors: Gupta A. Das
Published: March 2006

A combination of an analytical model for the free‐surface fluctuation and a numerical model for the interface fluctuation has been formulated for transient characteristics of salt‐water interface considering four different boundary conditions in the form of exciting functions imposed on the upstream source of fresh‐water supply. The one‐dimensional analytical model has been solved using Laplace transform, and the theory of residues and the results are expressed in terms of an infinite series and an error function. The numerical model gives the fluctuation of the interface for the known free‐surface profile; the interface location at the upstream boundary is specified on the condition that any fluctuation in the water table causes a net flow component in the vertical direction at that section. In comparison with laboratory tests, the method appears to be a reasonable approximation of the fluctuating phenomena for practical applications, except for consideration of time lag for interface response which needs further investigation.
AN IMPROVED METHOD FOR SLUG TESTS IN SMALL‐DIAMETER PIEZOMETERS
Authors: Patterson R. J. , Devlin J. F.
Published: March 2006

. The use of a small packer in slug tests can improve the quality of time versus head level measurements, particularly during the important early stages of the test. The packer is placed in the piezometer below the static water level and inflated. Water is then added to the piezometer until it is full to the top of the casing. The packer is deflated and the times for the water level to reach selected depths are measured with an electric sonde.
A Multistage Model for the Development of Hydrochemical Zonation in Chalk Ground Waters
Authors: Howard K.W.F.
Published: March 2006

Ground waters from the Cretaceous Chalk of east‐central England display hydrochemical zonation comprising four water types. These are, in the general direction of ground‐water flow; Type I – calcium bicarbonate (CaHCO3) waters undersaturated with respect to calcite, Type II – CaHCO3 waters saturated with respect to calcite, Type III – waters showing sulfate (SO4) reduction and softening by ion exchange, and Type IV – saline waters. At first appearance these water types may be interpreted as related members in the classically recognized, long‐term sequence of natural chemical evolution of subsurface waters. This simple model, however, cannot be reconciled fully with all aspects of the hydrochemistry. For example, there is no satisfactory process that could explain an apparent depletion of chloride when moving from Type I to Type II waters, and transitional boundaries are absent between water Types II and III, and Types III and IV. Furthermore, the model lacks credibility in an area where recent geological events have radically disturbed the regional ground‐water flow regime. An alternative hydrochemical zonation model is proposed in which each water type evolves independently of adjacent water types as a function of its own unique aquifer flow history. This multistage model is supported by tritium and radiocarbon evidence and can be related to probable changes in the regional flow regime during the past 125,000 years.
Distribution of Carbonates, Bicarbonates, and pH Values in Ground Water of the Nile Delta Region, Egypt
Authors: El Ghandour M.F.M. , Khalil J. B. , Atta S. A.
Published: March 2006

The carbonate ions are present in the ground water of the Nile Delta region in very small amounts (0–96 ppm). These ions decrease or may be absent in the northern parts of the Delta. The bicarbonate contents range between 0 and 738 ppm, depending on the amount of CO2 in water and following nearly the same trend as that of the carbonates. The pH values range between 5.5 and 8.5, where the increase of salinity content in the northern and western parts leads to its reduction, and the reverse happens towards the southern and eastern directions where the salinity decreases.
The Role of Specific Yield in Ground‐Water Recharge Estimations: A Numerical Study
Authors: Sophocleous Marios
Published: March 2006

This paper numerically demonstrates and quantifies the importance of capillary‐fringe and variable specific yield phenomena in ground‐water recharge estimations. A one‐dimensional numerical experiment consisting of a soil either with a capillary fringe or without it was set up using a finite‐element code. A prescribed infiltrating flux was superimposed on top of the soil column, and the resulting unsaturated‐saturated water flow was observed. By assuming a single value for specific yield, recharge is usually overestimated. For two cases considered in this study, the errors involved in ground‐water recharge estimations by using such an assumption ranged from 88 to 330 times the simulated recharge, when variable specific yield is considered. This study also clearly demonstrates the effect of a constant specific yield value on the behavior of the water table rise, the total amount of which as well as the rate of such rise are underestimated under that assumption. In addition, under that assumption, the timing of the water table rise is out of phase with the timing of recharge events.
LGWRES – LIFE OF GROUND‐WATER RESERVES
Authors: Rayner Frank A.
Published: March 2006

Abstract. LGWRES is a simplistic program, for the HP‐41C series of programmable calculators, to determine the lifetime of ground‐water reserves in years; total use over the lifetime of the reserves; precentage of domestic and agricultural uses; additional years of possible agricultural use realized by dedicating the domestic use to agriculture; and percentages of total use, domestic use, and agricultural use that could be sustained by annual replenishment to the ground‐water reserves, within the “safe yield” concept.
Aquifer Test Analysis in Nonradial Flow Regimes: A Case Study
Authors: Smith Ellen D. , Vaughan Nancy D.
Published: March 2006

A low‐rate aquifer pumping test was conducted in a folded and fractured limestone formation in the Conasauga Group of East Tennessee. An elongate drawdown pattern was observed, suggesting that pumping response was controlled by a highly conductive zone associated with a pair of anticlinal folds that bisect the test site. This drawdown pattern, the nonlinearity of graphs of observation well drawdown versus the log10 of time, and the existence of a linear relationship between drawdown and the square root of pumping time indicate that flow in response to pumping was nonradial. Thus, use of pumping test interpretive techniques based on radial flow models would be invalid. This situation may occur frequently when pumping tests are done in low‐permeability media, because fractures and other discontinuities often dominate the hydraulic behavior of low‐permeability media.

The solution technique used to estimate aquifer parameters (Gringarten and Witherspoon, (1972) treats the fold axes as a highly conductive vertical fracture in an anisotropic matrix of much lower hydraulic conductivity. The complexity of both the site and the solution technique necessitated iterative trial‐and‐error variable substitution to estimate aquifer parameters. The resulting solution includes estimates of matrix transmissivity in two directions, the storage coefficient of the matrix, and the effective length and location of the master fracture. Estimates of hydraulic parameters lack the apparent precision of values that would be generated by radial flow techniques, but they are consistent with geologic conditions at the site and present a clearer picture of the hydrogeologic regime than could be obtained with other investigative techniques. The solution technique used, whose field application has not been described previously in published literature, makes it possible to interpret the results of aquifer tests in complex hydrogeologic settings. This and related analytical techniques for other nonradial flow situations may prove useful in other hydrogeologic investigations in low‐permeability media affected by folds, faults, fractures, or solution channels.
Relations Between Aquifer Electrical and Hydraulic Properties
Authors: Kelly William E. , Frohlich Reinhard K.
Published: March 2006

The primary factor controlling material‐level relations between aquifer electrical and hydraulic properties in the clay‐free aquifer materials of southern Rhode Island is an inverse relation between in‐situ porosity and grain size. In‐situ density, grain size and laboratory hydraulic conductivity data support this conclusion. Relations between either layer resistivities and hydraulic conductivity, or a Dar Zarrouk parameter and transmissivity, are influenced by aquifer layering and the position of the aquifer layer relative to nonproducing layers. In the study area, the best relations between electrical and hydraulic properties are obtained where the transverse resistance of the aquifer is measured.
Aquifer‐Parameter Evaluation from Variable‐Rate Pumping Tests Using Convolution and Sensitivity Analysis
Authors: Butt M. A. , McElwee C. D.
Published: March 2006

The reliability of predictive and management models for ground water would be improved by better aquifer‐parameter estimation. As progress continues in the use of computers to simulate ground‐water systems, parallel progress must occur in data collection and analysis. Among the various methods available for the determination of aquifer parameters, pumping tests occupy a prominent position. The maximum advantage is gained from a pumping test when geological knowledge of the aquifer and the analysis of aquifer test data complement each other. This paper presents a technique involving the use of convolution and sensitivity analysis to obtain the “best fit” of aquifer parameters in a least‐squares sense from a pumping test with variable pumping rate. The method also can be used to analyze the residual drawdown data obtained during the recovery period. In addition, this method can also analyze drawdown and recovery data conjunctively. Constant drawdown and variable discharge data of artesian flowing wells also can be analyzed by this method. The method is straightforward, quick, inexpensive, and is always objective. No graphical plots or graphical interpretations are needed. As a measure of error, the rms (root‐mean‐square) error in drawdown is calculated along with the correlation coefficient between pumping‐test data and the theoretically generated data, using the converged values of transmissivity and storage coefficient.
Analysis of Steady‐State Flow in Semiconfined Aquifers: A New Approach
Authors: Gupta S. K. , Sharma P.
Published: March 2006

We show that in the case of semiconfined aquifers the ratio of steady‐state drawdown to its gradient with respect to the logarithm of radial distance from the pumping well, i.e. sm/(δsm/δ log10 r), determines the transmissivity of the aquifer. A new method for evaluation of aquifer parameters utilizing this principle is proposed. As the method does not involve curve matching, it avoids subjectivity. We illustrate the method with an example.
A COMPUTERIZED GROUND‐WATER RESOURCES INFORMATION SYSTEM
Authors: Monaghan G. William , Larson Grahame J.
Published: March 2006

Abstract. The MCGRIB system is a computerized data base of hydrogeologic information recorded in drillers' logs. It also includes software that allows the user to display hydrogeologic data for any specified area in tabular or map form. Although the system is designed mainly for glaciated regions it can be adapted to almost any geologic setting. The main advantages of the system are that it can be updated regularly and can rapidly provide pertinent information about subsurface hydrogeologic conditions.
The Ratio, Transmissivity/Storativity from Electric Analog Values of Streamflow
Authors: Sander John E.
Published: March 2006

Relatively little work has been done using streamflow data as a means of estimating hydrologic parameters such as transmissivity and storativity. An approach to this problem utilizing the physical insight offered by electric analog modeling techniques has been developed with streamflow data from two small drainage basins in northwest Virginia. Streamflow modeling has produced regional estimates of the ratio of transmissivity to storativity, and results from each region indicate this ratio to be larger than expected. This discrepancy is resolved by assuming that the drainage basins contain only a small percentage of permeable rock, and this assumption suggests a further use of the model to estimate the percent of permeable rock in a watershed. The analog approach presented here shows potential for further development using digital computer methods.
Limestone Influences on Physical and Chemical Features of a Mountain Stream
Authors: Larson Gary L. , Mathews Raymond C. , Herrmann Ray
Published: March 2006

Influences of limestone on physical and chemical characteristics of Abrams Creek in Cades Cove, Great Smoky Mountains National Park, were investigated from February to July 1977. Infiltration of stream water into subsurface permeable limestone conduits caused reduced and intermittent surface flow within the middle reach of the Cove. At the downstream (west) edge of the Cove, inflowing waters characteristically warmed the stream in winter and cooled it in summer and increased stream conductivity, total hardness, and pH. Management activities in the Cove did not appear to appreciably affect the chemistry of the aquatic system downstream relative to the large effects of limestone substrate.
Algorithm for Surface/Ground‐Water Allocation under Appropriation Doctrine
Authors: Lllangasekare Tissa H. , Morel‐Seytoux Hubert J.
Published: March 2006

A stream‐aquifer simulation model was developed to evaluate different conjunctive use management strategies in the South Platte River in Colorado. A component of this model simulates the allocation of surface and ground water for agricultural use. The water law based on the doctrine of prior appropriation provides the basic framework for water allocation in the study area. The physical sequence in which the river diversions are located along the river is different from the sequence in which the water has to be allocated according to the priority of rights. An algorithm is designed to allocate the river flows computed by the physical simulation component of the model to the appropriators according to the water rights and other imposed criteria as specified by the conjunctive management scheme under study. The algorithm is demonstrated on a management problem involving the evaluation of a streamflow augmentation scheme in the study reach.
Determination of Aquifer Parameters by the Slope‐Matching Method
Authors: Sen Zekâi
Published: March 2006

A method has been developed by which the slope between any two successive data points on a time‐drawdown plot can be used for determining aquifer parameters in nonleaky and leaky aquifers. The method yields values of transmissivity and storage coefficient which are in good agreement with the results of the classically known techniques. The method of slope analysis offers several advantages in its use. These advantages include the following: Changes in values for the aquifer parameters that might occur during a pumping test can be identified. Confidence limits can be calculated for average values of aquifer parameters. The method yields meaningful aquifer parameter estimates even for short duration pumping tests. Subjective interpretation of the data is minimized.
Analytical Modeling of Ground‐Water Impacts by Mining
Authors: Koch Donald
Published: March 2006

The equation for two‐dimensional, vertically averaged steady‐state flow to a finite‐length line sink, a semiempirical expression for the radius of influence, and the theory of superposition are used to predict the impacts of excavations on ground‐water flow patterns. The algorithm provides a rapid method for estimating the inflow to mine pits, and the impact of mines on the potentiometric surface. An accurate expression for the radius of influence is developed by comparison with analytical and finite‐difference model solutions. The algorithm is an accurate estimate of drawdowns at longer times, when the steady‐state approximation is appropriate.
A Solute‐Transport Simulation of Brackish‐Water Intrusion Near Baltimore, Maryland
Authors: Chapelle Francis H.
Published: March 2006

Brackish‐water contamination of the Patuxent aquifer has been a serious water‐quality problem in Baltimore, Maryland, since the early 1900's. The Patuxent aquifer presently contains a circular plume of brackish‐water contamination that is about 5 miles in diameter. This plume is centered on the Patapsco River estuary and is characterized by chloride concentrations that range up to 5,000 milligrams per liter. Borehole data demonstrate that the Arundel Clay Formation, which overlies the Patuxent and functions as a confining bed, has been breached by Pleistocene river channels in the Baltimore area. These erosional channels, which have been subsequently filled with relatively permeable sediments, provide conduits for brackish water to seep from the Patapsco River into the Patuxent aquifer when aquifer water levels arc lower than river water levels.

A two‐dimensional areal solute‐transport model of the Patuxent aquifer was used to estimate the future movement of the brackish‐water plume based on alternative strategies of aquifer use. Model simulations suggest that the plume will not spread rapidly if present pumping patterns are continued. Furthermore, sharply curtailing pumpage in the Baltimore area will probably not reduce the size of the plume, although this strategy may slightly decrease the spreading rate. While the plume is presently remaining nearly stationary, new pumping centers southeast of Baltimore could cause brackish water to migrate in that direction, significantly increasing the size of the plume.
A Radial Injection Tracer Experiment in a Confined Aquifer, Scarborough, Ontario, Canada
Authors: Palmer Carl D. , Nadon Robert L.
Published: March 2006

A radial injection tracer experiment was conducted in Scarborough, Ontario, as part of a program to evaluate the feasibility of using a confined aquifer, underlying the Canada Centre building site for the storage of chilled and/or heated water for a seasonal thermal energy storage system. Water was injected into the aquifer for five hours before a salt solution was added as a tracer. This tracer was injected into the aquifer over a period of four hours at a rate of 22.7 1/s. Injection of the water into the aquifer continued for an additional 1 5 hours following injection of the salt solution. Samples were collected from a monitoring well located 6.54 meters from the injection well. A sampling device was installed prior to the injection experiment to permit the collection of water samples at different elevations within the screened portion of the monitoring well. The samples which were collected at five different elevations at various times, both during and following the salt injection, were analyzed for specific conductance and chloride concentration. The data suggest that the aquifer is inhomogeneous and that the ratio of the hydraulic conductivity to porosity increases from the lowest sampling port to the highest sampling port near the top of the aquifer. A linear relationship was obtained between the time of arrival of the tracer and the apparent resistivity of the formation. This linear relationship was used to calibrate the apparent resistivity log of the injection well to provide a continuous characterization of the vertical variation in the hydraulic conductivity/porosity ratio across the full thickness of the aquifer. Data analysis also suggests that the dispcrsivity parameter varies linearly with the time of arrival of the tracer. The combination of geophysical logs with tracer experiments may permit detailed characterization of the hydraulic properties of aquifers.
Diagnostic Hydrologya
Authors: De Wiest Roger J. M.
Published: March 2006

This paper examines two eases of surface‐water/ ground‐water interrelationships, one in Beaufort County, North Carolina and one in Ramona, California. In each case the author has to make a differential diagnosis between alternate solutions rendered by hydrologic methods.

In the first ease, the author proves that the pumping and subsequent wastage to the ocean of 65 mgd in order to operate the Texas Gulf Sulphur phosphate mine, in all likelihood poses no threat to the environment.

In the second case, the author has attempted to obtain, by means of the theory of ground‐water flow, an estimate of the physiographic volume of the Santa Maria creek ground‐water basin in Ramona. He has submitted the outcome of his calculations to the test of compatibility with the results of an actual pumping test, and with pumping records made available by the Ramona Municipal Water District. The outcome shows a water storage capacity of the order of 4,600 AF for the entire basin.

In order to correlate recharge of the basin directly with the precipitation on the basin, a hydrograph analysis has been done for the 20 largest runoff‐producing months of the streamflow records 1965–1982. From this study it follows that the average (annual) recharge to the basin is of the order of 1,340 AF/yr and that the physiographic volume, as derived previously, is amply adequate to absorb this recharge.
SPEEDING IT UP IN BASIC
Authors: Logan John
Published: March 2006

Abstract. Execution time of many programs can be markedly shortened by (a) defining frequently used constants in assignment statements or placing them in arrays and by (b) avoiding or minimizing the use of exponentials.
A Hydrologic Budget Analysis for the Nile Valley in Egypt
Authors: Attia Fatma A. R. , Allam Mohamed N. , Amer Abdel Wahab
Published: March 2006

A two‐dimensional finite‐element model has been adapted to simulate the aquifer underlying the Nile Valley of Egypt. Calibration of the model led to the determination of the interaction between the ground water and the Nile surface water. Results obtained from the model were compared with those obtained from simple hydrologic budget analyses and were found to be quite comparable. The model is, thus, considered to adequately represent the ground‐water system of the Nile Valley and may be used to forecast the effects of managing the integrated ground‐water/surface‐water system.
Ground‐Water Recharge and Its Effects on Nitrate Concentration Beneath a Manured Field Site in Pennsylvania
Authors: Gerhart James M.
Published: March 2006

Ground‐water recharge to a shallow, unconfined, fractured dolomite aquifer underlying agricultural land in Lancaster County, Pennsylvania occurs by two mechanisms. Direct recharge occurs through pathways such as near‐surface bedrock fractures and sinkholes, and affects dissolved nitrate concentration of ground water within two to three days; its effects last only about one week. Gradual recharge occurs through small channels and pores in the unsaturated zone and affects dissolved nitrate concentration for several weeks or more after the effects of direct recharge have dissipated. Whether recharge causes an increase or decrease in dissolved nitrate concentration depends on the amount of nitrogen‐rich manure spread on the site prior to the storm. Direct recharge from a storm in March 1984, a month in which 18 tons of manure were spread, resulted in a rapid decrease in dissolved nitrate concentration of about 2.5 milligrams per liter (mg/1) as nitrogen. Direct recharge from a storm in May 1984, after 384 tons of manure had been spread in April, resulted in a rapid increase in dissolved nitrate concentration of about 3 mg/1 as nitrogen. Concentration changes caused by gradual recharge several weeks or more after the storms were of the same magnitude as those caused by direct recharge during the storm.
Finite‐Difference Grid for a Doublet Well in an Anisotropic Aquifer
Authors: Miller Robert T. , Voss Clifford I.
Published: March 2006

The U.S. Geological Survey is modeling hydraulic flow and thermal‐energy transport at a two‐well injection/ withdrawal system in St. Paul, Minnesota. The design of the finite‐difference model grid for the doublet‐well system is complicated because the aquifer is anisotropic and the principal axes of transmissivity are not aligned with the axis between the two wells.

An analytical solution for flow in a doublet‐well system in an infinite anisotropic aquifer was employed in the design of a grid with artificial boundaries placed in the midst of the flow field. Flow‐net analysis was used to determine water flux across an cquipotential boundary and to assign approximate flux values at model boundaries. This enabled the simulation of the effects of the entire flow field, although only a small part was modeled.

The validity of the flux values at the model boundaries for the isothermal case was tested by simulation of an eight‐day injection test of ambient‐temperature water. Model‐computed pressures compared very favorably with field‐observed pressures. The validity of boundary‐flux values also was tested for nonisothermal conditions by simulation of injection of 300o F water at 300 gallons per minute for eight days.