bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of Constant‐Rate Drawdowns from Stepped‐Rate Pumping Tests
Authors: van der Kamp G. 
Published: August 2005

ABSTRACTDrawdown and recovery data obtained for stepped‐ rate pumping tests can be used to calculate the drawdowns that would occur if the test were carried out a constant rate without stopping. The recovery phase of constant‐rate pumping tests can be analyzed by the same method because cessation of pumping can be treated as a step change of pumping rate. The calculation assumes only that pumping during each step is at a constant rate, and that the principle of superposition is applicable, i.e., that the ground‐water system is linear and time‐invariant. It does not depend on the availability of theoretical expressions for the drawdown due to pumping. The calculation can be carried out for as long as water‐level measurements are continued; however, possible errors in the values of calculated drawdown increase with increasing time, thus limiting the practical length of time for which the calculated values are reliable.The constant‐rate drawdown curves characterize the response of the linear time‐invariant ground‐water system to pumping. They can be used for the determination of formation parameters if an appropriate theoretical model is available. They can also be used directly to predict drawdowns, and the scope of this application can be broadened by use of the reciprocity principle. In either case the use of recovery data can significantly extend the effective duration of pumping tests.
Septic Tank Setback Distances: A Way to Minimize Virus Contamination of Drinking Watera
Authors: Yates Marylynn V. , Yates S. R. 
Published: August 2005

ABSTRACTSeptic tanks are the most frequently reported causes of contamination in ground‐water disease outbreaks associated with the consumption of untreated ground water in the United States. The placement of septic tanks is generally controlled by county‐wide or state‐wide regulations, with little consideration given to the local hydrogeologic, climatic, and land‐use conditions. Using the travel time necessary to achieve a seven‐order‐of‐magnitude reduction in virus number as the criterion, a wide range of septic tank setback distances (from less than 15 m to greater than 300 m) were calculated for a part of the Tucson Basin. This study makes use of disjunctive kriging to calculate the conditional probabilities associated with the setback distance estimates. The results are presented in two different ways: first, given a setback distance (e.g., prescribed by law) the probabilities that the level of viruses will be within acceptable limits are calculated; and second, the desired probability level is specified (e.g., 90%) and the setback distances required to achieve that level of confidence that the water will be free of virus contamination are calculated. The methods have potential for use by local government officials for land‐use planning purposes.
Detergent Formula Effect on Transport of Nutrients to Ground Water from Septic Systems
Authors: Alhajjar Bashar J. , Harkin John M. , Chesters Gordon 
Published: August 2005

ABSTRACTTwo groups of new septic systems in coarse‐textured soils overlying shallow ground water were monitored for two years to determine the potential of contamination of individual ground‐water supply from the use of phosphate‐ built (PO4) or carbonate‐built (CO3) detergents. The distribution of nutrients and chloride in the shallow aquifer were examined to trace contamination from the septic systems.The data were evaluated statistically, and a stochastic nutrient transport model was compiled to simulate ground‐ water contamination by nutrients for a five‐county region. The stochastic modeling of the data showed that neither detergent caused delivery of total phosphorus to ground water in concentrations above 0.1 mg/1 as P. However, total nitrogen was removed more efficiently from systems receiving PC4‐built than CO3‐built detergents. The total nitrogen from septic systems reached the ground water in concentrations of 39 and 69 mg/1 as N from PO4‐ and CO3‐built detergent use, respectively, The detergent formula has a substantial effect on ground‐water contamination by nitrogen from septic systems.
The Bouwer and Rice Slug Test — An Updatea
Authors: Bouwer Herman 
Published: August 2005

ABSTRACTThe Bouwer and Rice slug test was developed to measure aquifer hydraulic conductivity around boreholes (production, monitoring, or test wells). The wells can be partially penetrating and partially screened, perforated, or otherwise open. The slug test can be based on quickly with‐ drawing a volume of water from the well and measuring the subsequent rate of rise of the water level in the well, or by adding a slug of water and measuring the subsequent rate of fall of the water level in the well. While originally developed for unconfined aquifers, the method can also be used for confined or stratified aquifers if the top of the screen or perforated section is some distance below the upper confining layer. Anomalies (“double straight line effect”) sometimes observed in the measured rate of rise of the water level in the well are attributed to drainage of a gravel pack or developed zone around the well following lowering of the water level. The effect of this drainage can be eliminated by ignoring the early data points and using the second straight line portion in the data plot for calculation of hydraulic conductivity. The method is applicable to any diameter and depth of the borehole, provided that the dimensions of the system are covered by the ranges for which the geometry factor Re has been worked out. The smaller the diameter of the hole, however, the more vulnerable the results will be to aquifer heterogeneities and to inaccuracies in estimating effective well diameters. Computer programs for rapid processing of the field data have been developed.
The Coastal Ground‐Water Boundary
Authors: Urish Daniel W. , Ozbilgin Melih M. 
Published: August 2005

ABSTRACTIn many island and coastal ground‐water problems, the position of the ground‐water/free sea‐water interface is an essential, but highly dynamic boundary. The fluctuating boundary commonly is simplified to a fixed position in problem formulation. This fixed position is frequently taken as the location of local mean free‐water level (mean sea level) in the adjacent salt‐water body. However, tidal fluctuation and wave runup on a sloping beach cause mounding of sea water in the upper beach with a consequent effective mean sea level as much as two feet higher than local mean sea level. This phenomenon is particularly important in small islands and coastal situations where the ground‐water flow pattern is highly dependent on the position of the effective boundary both vertically and horizontally. In coastal hydrological situations, a good approximation for the effective vertical position, i.e. effective mean sea level, of the ground‐water/free sea‐water boundary is the mean equivalent salt‐water head in a deep discretely screened piezometer located in the beach near the upper swash line. The veracity of this technique is demonstrated by the results of field research in a New England barrier beach.
The Hydrologic Responses to Development in Regional Sedimentary Aquifers
Authors: Johnston Richard H. 
Published: August 2005

ABSTRACTThe hydrologic response to development of three of the most heavily pumped sedimentary aquifer systems in the United States is similar in some aspects and different in others. In the semiarid West, an unconfined sand aquifer and a confined sand and clay aquifer system have been subjected to withdrawals that are far greater than predevelopment recharge rates. As a result, the aquifers have large losses of ground water from storage. In the humid East, pumpage from a carbonate aquifer system has resulted in induced recharge and diversion of natural discharge with insignificant loss from storage. However, the following responses to development are common in all three aquifer systems: (1) ground‐water circulation has increased,(2) rates of recharge have increased—mostly due to recirculation of pumped ground water, or infiltration of imported surface water used for irrigation in the semiarid West,(3) locations of recharge areas have changed, and (4) natural discharge has decreased.Regional water‐level declines associated with ground‐ water development are inevitably accompanied by some combination of elastic compaction of aquifer material, inelastic compaction of fine‐grained sediments and land subsidence, dewatering of aquifer material near pumping centers, and induced formation of sinkholes. The degree to which these changes occur is dependent on: (1) rates of pumping in relation to available recharge, and (2) lithology, specifically the proportion of sand, gravel, silt, clay, and carbonate rock that comprise the aquifer system.
Estimating Water‐Table Altitudes for Regional Ground‐Water Flow Modeling, U.S. Gulf Coast
Authors: Williams Thomas A. , Williamson Alex K. 
Published: August 2005

ABSTRACTWater‐table altitude, a controlling factor for ground‐ water flow, was estimated from detailed topographic data by subtracting the estimated depth‐to‐water. Land‐surface altitude of the Coastal Plain in the south‐central United States varies from 0 to more than 800 feet above sea level. Predevelopment depth‐to‐water in 6,825 wells less than 150 feet deep averages 25.7 feet (standard deviation, 19.5 feet). Most water‐table‐altitude variation is due to variation in land‐surface altitude and not due to variation in depth‐to‐ water. Digital topographic data, from 1:250,000 scale maps for every 30 seconds of latitude and longitude are available for the continental United States. About 90 altitudes were averaged for each 25‐square‐mile block of a rectangular grid used for ground‐water flow modeling. Multiple linear regressions of predevelopment water‐level data and topographic data were used to derive empirical equations relating water‐table altitude to topography.The regression method was more consistent, efficient, and accurate than manually digitizing values from manually contoured water‐table maps. Water‐table maps usually are prepared from few data that are concentrated in topographically flat areas. Manually digitizing water‐table maps on a regional scale introduces additional error. About 35 percent of the water‐table altitudes obtained manually were greater than average land‐surface altitudes from topographic data. The mean difference between water‐table altitudes from the two methods was less than 10 feet, which indicates no systematic error was incorporated in the regression method.
The Disposal of Nuclear Waste: A Problem in Mass Management?
Authors: Domenico P. A. , Lerman A. , Bartlett J. W. 
Published: August 2005

ABSTRACTA reference repository is examined for environmental compliance utilizing minimum performance standards as established by the Nuclear Regulatory Commission and the Environmental Protection Agency. These standards stipulate the amount of time the radionuclides must be retained in the barrier, the acceptable release rates from the barrier, and the acceptable mass release that can be registered at the accessible environment over a 10,000‐year time frame. The only natural, or geologic barrier standard specified is a minimum ground‐water travel time of 1000 years from the engineered barrier to the accessible environment. Other natural barrier processes including geochemical retardation and mass transfer, dilution, and dispersion are not specified. In attempting to determine the role that these unspecified components must play in order to comply with the mass release standard, we find that their role is minimal to the extent that virtually any rock type that can satisfy the minimum ground‐water travel time of 1000 years will satisfy the mass release requirements at the accessible environment. Full compliance with a concentration standard at the accessible environment requires that the nuclides contained within the larger inventories be fully contained with the controlled zone between the engineered barrier and the accessible environment
Identifying Fracture Interconnections Between Boreholes Using Natural Temperature Profiling: I. Conceptual Basis
Authors: Silliman S. , Robinson R. 
Published: August 2005

ABSTRACTIn situ delineation of fracture characteristics is a difficult and often time‐consuming task. Several advantages would be gained from the development of simple field techniques which provide direct evidence of such parameters as fracture connectivity, fracture orientation, or fracture aperture. In this paper, such a technique for delineation of fracture connectivity between boreholes is introduced. The technique is based on utilizing the natural variation of water temperature within the subsurface as a natural ground‐water tracer. In this technique, thermal response in observation boreholes induced by local pumping or injection is related to the location of interconnected fractures. The technique provides several advantages including simple equipment and time requirements, direct evidence of fracture flow between boreholes, and the ability to test without contaminating a field site. The major limitations of the technique are related to the volume of fluid movement within an observation hole and are controlled by the geometry of the flow field in the vicinity of the pumping/ injection borehole. Two case studies are briefly outlined demonstrating application of the technique to both a fractured granite and a fractured dolomite. Part II of this paper (Robinson and Silliman, in preparation) contains a detailed discussion of the application of this technique to the second, fractured dolomite, case study.
Physical Controls on Hydrochemical Variability in the Inner Bluegrass Karst Region of Central Kentuckya
Authors: Scanlon B. R. 
Published: August 2005

ABSTRACTAreal and temporal variations in physical and chemical characteristics of ground water in the Inner Bluegrass Karst Region of central Kentucky were used to evaluate physical controls on hydrochemical variability. The karst region consists of flat‐lying interbedded limestones and shales. Physical attributes of the aquifer were assessed on the basis of spring discharges, static water levels in wells, and pumping tests. Areal and temporal variations in ground‐ water chemistry were determined from major‐ion analysis of water samples from 15 springs and 24 wells over a 17‐ month period.Water samples were divided into three chemical types on the basis of the relative concentrations of the dominant ions; Ca‐Mg‐HCO3, Na‐HCO3, and Na‐Cl water. Ca‐Mg‐HCO3 water was divided further on the basis of Ca/Mg molar ratios into Ca subtype water (Ca/Mg > 6) and Ca‐Mg subtype water (Ca/Mg < 6). All springs are characterized by Ca subtype water. Pumping tests show that hydraulic conductivities in zones of Ca‐Mg‐HCO3 water are significantly higher than those in zones of Na‐HCO3 and Na‐Cl water. There is no regional trend in the distribution of these water types.Temporal fluctuations in water chemistry correlate with seasonal fluctuations in recharge. Large seasonal variations in ionic concentrations occur primarily in Ca subtype water. Hydraulic conductivities, seasonal variations in ionic concentrations, and TDS suggest that ground‐water residence time is the primary control on the occurrence of the different water types. Differences in residence time are attributed to the presence of discontinuous, horizontal shales that control the rate and depth of active groundwater ciculation.
Numerical Identification of Parameters in Leaky Aquifers
Authors: Yeh Hund‐Der , Han Hung‐Yuang 
Published: August 2005

ABSTRACTA method using the nonlinear least‐squares and finite‐ difference Newton's method is presented to identify the parameters from pumping tests in homogeneous and isotropic leaky aquifers both for the situations with and without storage effects in the aquitard. Based on the least‐ squares approach, the sum of the squares of differences between the observed drawdowns and predicted drawdowns using the estimated parameters is minimized. The finite‐ difference Newton's method is used to solve the system of nonlinear least‐squares equations for the unknown aquifer parameters.Comparisons of the results among the proposed method, graphical method, and sensitivity analysis method when analyzing various data are presented. The proposed method has the merit of good accuracy and quick convergence from some initial guesses.
Dissimilatory Nitrate Reduction in a Waste‐Water Contaminated Aquifer
Authors: Bulger Paul R. , Kehew Alan E. , Nelson Richard A. 
Published: August 2005

ABSTRACTGround water beneath the McVille, North Dakota Municipal Waste‐Stabilization Ponds was studied to determine the chemical effects of seepage on a shallow unconfined aquifer. Relatively coarse‐grained glaciofluvial sediments underlie the site and facilitate transport of partially treated waste water to the water table, altering the local ground‐water chemistry.The plume resulting from infiltration contains elevated levels of dissolved organic carbon (DOC) and ammonium in areas of low redox potential. The presence of nutrients in waters of low redox potential promotes the growth of anaerobic bacteria. Ground water containing high nitrate concentrations, due to leachate from an adjacent abandoned landfill, occurs upgradient of the ponds. These high nitrate waters, traveling downgradient, mix with the low redox potential ground water beneath and downgradient of the lagoon. Ammonium concentrations, downgradient of the waste‐stabilization ponds, are greater than ammonium levels within the ponded waste water. The abundant microbial population appears to utilize DOC and nitrate as nutrients for growth and energy. The utilization of nutrients occurs in a redox reaction, in which nitrate is apparently reduced to ammonium and carbon is oxidized. The increase in ammonium levels and decrease in nitrate levels suggests nitrate is not assimilated into cell tissue, but instead dissimilatory nitrate reduction to ammonium takes place. Dissimilatory reduction refers to reduction of a compound for its energy yield, without conversion of the compound to biomass (Ceazan et al, 1984).
Expert Opinion and Ground‐Water Quality Protection: The Case of Nitrate in Drinking Water
Authors: Rajagopal R. , Tobin Graham 
Published: August 2005

ABSTRACTGround‐water protection strategies have been constrained by the limited consideration of varied and new options relevant to particular problems. Consequently, management practices have tended to maintain the status quo regarding legislation and water‐quality standards. To examine the responses to specific issues, we presented an analysis of the problem of nitrate contamination of ground water in the Midwest to a community of experts. Ninety‐seven individuals, through a formal questionnaire, responded to a variety of questions pertaining to the issue. They showed definite preferences in dealing with certain aspects of the problem, although there was significant variability in responses due to such factors as length of ground‐water‐related professional experience and residential status. It was clear that respondents preferred immediate preventive or corrective action in a world of incomplete knowledge over extensive research; were willing to undertake personal action to seek nitrate‐free water rather than wait for official action; and favored local and state level involvement over federal intervention. Findings based on this survey research can be used effectively in the planning of future work to establish actual preferences in communities with serious nitrate contamination problems.
Experimental Research on Permeability of Granular Media
Authors: Er‐Hui Zhao 
Published: August 2005

ABSTRACTThe coefficient of permeability or hydraulic conductivity is a basic parameter of a granular media. It is difficult to determine the coefficient of permeability because it depends on many factors. According to experiments and analysis, we think the permeability of a granular media results from the unified effect of an external factor—the hydraulic gradient, and internal factors—properties of the granular media itself and the fluid; therefore, the permeability of a granular media can be determined by a sieve analysis and physical characteristics of the fluid. Based on theoretical analysis and experiments, we advance a unified expression to calculate the coefficient of permeability of a granular media. The precision of the formula is up to practical requirements based on inspection of experimental data. The formula is
Geostatistical Estimation of Hydraulic Head Gradients
Authors: Philip Ross D. , Kitanidis Peter K. 
Published: August 2005

ABSTRACTThis paper describes a technique for estimating gradients of hydraulic head from scattered measurements of head. Gradients of hydraulic head control the flow of ground water in aquifers and their determination is an important part of any ground‐water investigation. A best linear unbiased estimator of hydraulic head is derived which allows direct estimation of head gradients and mean square estimation error. The hydraulic head is broken into continuous and discontinuous components. The discontinuous component, which represents random measurement error and small‐scale variability, is filtered from the measurements. The technique is applied to measurements of head in the Wolfcamp aquifer in northern Texas.
Horizontal Anisotropy of the Principal Ground‐Water Flow Zone in the Salinas Alluvial Fan, Puerto Rico
Authors: Quiñones‐Aponte Vicente 
Published: August 2005

ABSTRACTWell drawdown data from an anisotropic aquifer in the Salinas alluvial fan were collected and analyzed with a computer program called TENSOR2D. The program uses ordinary and weighted least‐squares optimization procedures to solve the system of simultaneous equations needed to define the theoretical transmissivity ellipse. Results from the alluvial fan aquifer at Salinas, Puerto Rico indicated that when applying the ordinary least‐squares method:(1) the major and minor transmissivity tensors are 52, 339 and 17,800 feet squared per day (ft2/d) respectively;(2) the square root of the major and minor diffusivity tensors are 12,066 and 7,036 ft2/d, (3) the ratio of horizontal anisotropy is 2·94 to 1·00, and (4) the direction of major anisotropy tensor is along a line 31 degrees west from the true north. From the application of the weighted least‐squares method: (1) the major and minor transmissivity tensors are 38,840 and 23,987 ft2/d, (2) the square root of the major and minor diffusivity tensors are 11,282 and 8,866 ft2/d, (3) the ratio of horizontal anisotropy is 1·62 to 1·00, and (4) the direction of major anisotropy tensor is along a line 28 degrees west of the true north. Prediction of drawdown data was made by coupling the anisotropy ellipse with the Hantush modified leaky‐confined or Theis model. Drawdown data predicted by using the theoretical directional diffusivity obtained with the weighted least‐squared fit gave a more accurate representation of the actual drawdown data than when using the test‐data directional diffusivity.