bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulated Salt‐Water Movement in the Nakhon Luang Aquifer, Bangkok, Thailand
Authors: Gupta A. Das 
Published: March 2006

ABSTRACTAnalytical 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

ABSTRACTAs 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

ABSTRACTWaters 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

ABSTRACTWater 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

ABSTRACTChemical 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

ABSTRACTUnsteady 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

ABSTRACTThe 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

Abstract. 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

ABSTRACTSubdividing 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

ABSTRACTA 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

Abstract. 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

ABSTRACTGround 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

ABSTRACTThe 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

ABSTRACTThis 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.
Aquifer Test Analysis in Nonradial Flow Regimes: A Case Study
Authors: Smith Ellen D. , Vaughan Nancy D. 
Published: March 2006

ABSTRACTA 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

ABSTRACTThe 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

ABSTRACTThe 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

ABSTRACTWe 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.
The Ratio, Transmissivity/Storativity from Electric Analog Values of Streamflow
Authors: Sander John E. 
Published: March 2006

ABSTRACTRelatively 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

ABSTRACTInfluences 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.