bluuebunny/crossref_metadata_2025_split huggingface dataset:
Airborne Geophysical Exploration for Ground Water
Authors: Paterson Norman R. , Bosschart Robbert A. 
Published: March 2006

ABSTRACTGeophysical methods have been used for many years to assist in hydrogeological exploration for ground water. For the direct detection of water‐bearing formations, the electrical resistivity method has been effective but relatively slow and costly.More recently, surveys have been conducted successfully with electromagnetic prospecting apparatus developed primarily for the mineral industry. Such equipment has the advantages of greater speed and portability, improved subsurface resolution, and better potential discrimination of conductive aquifers.Electromagnetic methods also can be applied from moving platforms, including fixed‐wing aircraft and helicopters. Detailed and regional surveys conducted in recent years for geological mapping and mineral exploration in Africa and elsewhere have revealed important information on the location and nature of water‐bearing formations and structures. Simultaneous measurements of the magnetic field have been used also to map faults and dikes of potential ground‐water significance.New, wide‐band, digital airborne equipment and processing systems are capable of carrying out rapid, inexpensive studies of subsurface formations to depths of at least 200 meters. Computerized interpretation techniques can produce maps of depth and electrical conductance of a variety of buried aquifers. This information can be of direct assistance to the hydrogeologist or hydrologist in the identification and development of underground‐water supplies.
Generation of Ground‐Water Age Distributions
Authors: Campana Michael E. 
Published: March 2006

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

ABSTRACTSubsurface air is a refuge for radon gas escaping from rock and soil surfaces, as well as from subsurface water. Where the subsurface air is confined in a zone by overlying poorly permeable material or by downward‐moving water, the radon can accrete and become mobile. The crystalline rocks of eastern United States contain granites and associated rocks that have moderate to low amounts of uranium source material; the amounts are sufficient for radon to emanate significantly from both the soil‐saprolite zone and the part of the underlying fractured rock above the water table.Both the soil‐saprolite confined air system and the fracture air system are nondescript and are erratic in size and shape from place to place and from time to time. They tend to have a gross horizontality because of blanket infiltration of precipitation and in some cases by crude layering of soil horizons or tension fracturing of bedrock.The pressure increases in the air systems chiefly as infiltrated water moves downward and as the water table rises. The radon‐laden air moves toward two types of low‐pressure chambers. One type of chamber is a house on sloping topography niched into the soil‐saprolite zone and perhaps into bedrock fractures. The other type is the unwatered fracture zone of a pumping cone of depression where overlying clays are less permeable. These two types of low‐pressure chambers have characteristics of vacuum cleaners, sucking in radon‐laden air.Conditions leading to high indoor radon concentrations are: (1) granites and associated rocks with normal or above normal amounts of uranium, (2) normal interconnecting fracture pattern, (3) a thin mantle of relatively impermeable clay soil, (4) repeated cycles of recharge and of a fluctuating water table in the fracture zone or in the overlying regolith, (5) indentation of buildings into soil and rock materials, and (6) building construction allowing relatively easy inflow of air from the subsoil and rock.
Hydraulic/Chemical Changes During Ground‐Water Recharge by Injectiona
Authors: Hamlin Scott N. 
Published: March 2006

ABSTRACTGround‐water recharge by injection of reclaimed water is a feasible method of improving ground‐water quality in the shallow aquifer system in the Palo Alto Baylands along the San Francisco Bay. Ground water was initially more saline than sea water. Reclaimed water was injected at a rate of 10 gallons per minute from June 5, 1980, to July 1, 1980. At the completion of injection, water from an observation well 31 feet from the injection well was 98 percent injected water‐in essence, fresh water.An abrupt rise in the water level in the injection well of about 1.5 feet during the initial injection test was the result of a 3.5 percent density difference between injected fresh water and saline ground water. The arrival of injected water at observation wells showed the same effect, allowing monitoring of chemical and hydraulic changes entirely through water‐level data.The initially sodic clays in the confining layer were expected to swell as the saline ground water (sodium source) was diluted by recharge water. The sodium ion causes excessive coordination with the hydronium ion (H3O+) in the clay lattice, resulting in expansion as the saline water is diluted. X‐ray diffraction analysis of clay samples soaked first in native and then in injected water showed this effect. Calcium replaces sodium and limits expansion.Prior to injection the saline ground water was supersaturated with calcite. Dilution, as injection proceeded, eventually produced an undersaturation of calcite. An increase in well specific capacity indicates that calcite dissolved from the aquifer matrix, improving hydraulic conductivity.
The Impact of the Dupuit‐Forchheimer Approximation on Salt‐Water Intrusion Simulation
Authors: Kemblowski Marian 
Published: March 2006

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

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

ABSTRACTThree case histories are presented to illustrate the problems encountered using some monitoring well installation, purging, and sampling techniques. Hollow‐stem auger‐ing was found to pose problems during the installation of monitoring wells in terms of potential for cross‐contamination of strata, the inability to emplace an adequate filter pack, the potential for smearing natural clays into sand and gravel strata, and the possible need for excessive purging of sediments that accumulate between sampling events. Cable tool drilling was found to allow construction of high quality wells, but was slow and expensive. Concern over the potential for increased emissions of noxious vapors from the borehole when drilling with the air rotary method prevented its use in situations where highly contaminated strata were likely to be encountered. A hybrid drilling technique, augering with temporary casing, was able to provide the advantages, and minimize the disadvantages, of the foregoing drilling methods.The installation of vertically separated clusters of monitoring wells lent important insights into the potential movement of a contaminant plume. Detailed aquifer tests provided needed information on the hydraulic behavior of the subsurface strata occupied by the plume so that potential pathways of contaminant transport could be more accurately identified. Obtaining reliable data from such tests depended greatly on the ability of each monitoring well to act as a high quality hydraulic observation well. The selection of drilling and installation techniques that ensured minimal disturbance of the near‐borehole environment provided the best guarantee of such performance.
Analysis of Hydraulic Gradients Across the Host Rock at the Proposed Texas Panhandle Nuclear‐Waste Repository Site
Authors: Bair E. Scott 
Published: March 2006

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

ABSTRACTThe Ramapo Fault is a major structural feature of northern New Jersey separating the Triassic‐age Newark Basin from the Precambrian Reading Prong. When the New Jersey Department of Transportation proposed extending Interstate Highway 287 north of Boonton, New Jersey, along the fault alignment, concerns were raised regarding the potential for the fault to act as a preferential source of ground‐water recharge to aquifers supplying domestic and industrial needs. It was feared that highway contaminants and spills could infiltrate the fault zone, be transported along the fault, and recharge the unconsolidated Pleistocene‐age buried valley aquifers, principally the Towaco Valley aquifer.As a result of these concerns, a detailed investigation was performed to determine the location and hydrogeologic character of the fault. Geologic mapping and geophysical techniques were employed to locate the fault prior to core drilling and packer testing of the fault. Geophysical logs were obtained from the borings to assist in characterization of the formation properties and to verify the fault location.The results of the investigation indicate that the Ramapo Fault has a calculated hydraulic conductivity of less than 1 × 10−7 cm/sec which was indistinguishable from the surrounding formations. It was concluded that the Ramapo Fault does not provide ground‐water recharge to the unconsolidated buried valley aquifers within the study area. The deltaic deposits overlying bedrock directly up‐gradient of the buried valley exhibited relatively high hydraulic conductivity (10−2 cm/sec) providing the major source of recharge to the unconsolidated aquifers in the Towaco Valley.
Applications of Universal Kriging to an Aquifer Study in New Jersey
Authors: Pucci Amleto A. , Murashige Jo Ann E. 
Published: March 2006

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

ABSTRACTIn recent years, several pesticide‐related contaminants have been detected in the ground waters of the State of Hawaii. Two soil fumigants previously used by pineapple growers, 1,2‐dibromo‐3‐chloropropanc (DBCP) and 1,2‐dibromoethane or ethylene dibromide (EDB), have been detected in several wells on Oahu and Maui. An impurity of the soil fumigant DD, 1,2,3‐trichloropropane (TCP), also has been detected in a number of wells. DBCP, EDB, and TCP are of particular concern to State public health officials due to known and possible unknown health effects associated with these compounds.The locations of the contaminated well sites on Oahu appear to be correlated with the areas of past and present pineapple cultivation when the ambient ground‐water flow pattern is taken into consideration. In addition, several large fuel pipeline leaks are located in the vicinity of the EDB contamination. In general, TCP contamination is more widespread than either DBCP or EDB contamination. TCP levels appear to be declining in Oahu water wells while EDB levels in the contaminated portion of southern Oahu appear to be increasing. The direction of temporal trends in DBCP concentration at present varies according to site.
Seepage Face Simulation Using PLASM
Authors: Potter Scott T. , Gburek William J. 
Published: March 2006

ABSTRACTAn unconfined aquifer variation of the Prickett and Lonnquist Aquifer Simulation Model (PLASM) has been modified to simulate the dynamics of seepage face development and compute flow rates therefrom. The modifications, based on hydraulic theory and operating within the framework of the original model, enable the model to simulate zones of seepage contiguous and noncontiguous to streams, lakes, or other points of ground‐water discharge. A simplistic overland flow routing procedure to move seepage flow downslope from points of discharge and permitting it to reenter where the water table is below the land surface was also incorporated.To determine the error associated with this discrete solution, the modified numerical model was compared to a series of analytically equivalent Dupuit‐Forchheimer‐based solutions. The numerical solutions from PLASM compare to the closed‐form solutions to within the uncertainty of the model's finite‐difference discretization. The comparisons indicate that errors in seepage face prediction result strictly from PLASM's inclusion of the D‐F approximations, not from the formulation of the numerical seepage face simulation routine. Finally, the modified PLASM was applied to a hypothetical watershed under dynamic conditions to demonstrate its capabilities.The unconfined aquifer version of PLASM works best in situations where both thickness‐to‐length ratio of the aquifer and land surface and water‐table slopes are relatively small, geometry typical of many real‐world watersheds. Under such conditions, the modifications developed are shown to logically and consistently simulate the extent, dynamics, and flow rates of seepage zones with minimum error.
A Horizontal Plane Source Model for Ground‐Water Transport
Authors: Galya Donald P. 
Published: March 2006

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

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

ABSTRACTThe benefits from ground‐water quality monitoring ultimately depend on the statistical methods used to analyze data. The methods must match both the information expectations of users and the characteristics of the water quality variables to which they are applied. The primary objective of regulatory ground‐water monitoring is detecting changes in quality. To select appropriate statistical tests for change, one must know whether the water quality variables of concern are seasonal, normally distributed, and serially dependent. This paper provides guidance in analyzing limited background data sets to determine these three characteristics.Recommended procedures to detect seasonality were pcriodograms, Student's t‐test, Mann‐Whitney test, analysis of variance, and Kruskal‐Wallis test. To test for normality, the skewness coefficient is recommended. To detect serial dependence, sample autocorrelation coefficients may be tested for significance.
The Politics of Ground‐Water Management Reform in Oklahomaa
Authors: Roberts Rebecca S. , Gros Sally L. 
Published: March 2006

ABSTRACTThis paper examines the politics of ground‐water management reform in Oklahoma. It argues that the geographic distribution of water supplies and uses significantly modifies the distribution of costs and benefits of reform among political constituencies. Effective restrictions on ground‐water withdrawals would raise large and immediate threats to irrigators and farm communities dependent on irrigation in western Oklahoma. Municipal and industrial water users, concentrated in eastern Oklahoma and reliant on more plentiful surface‐water supplies, would receive more diffuse, longer‐range benefits to management reform. These effects have significant implications for the politics of ground‐water management. The results of the analysis suggest that approaches taken to ground‐water management reform in Oklahoma, and the other eastern Ogallala states, may be more effective and realistic than might initially be thought.Oklahoma's present ground‐water law, adopted in 1973, is based on a utilization policy of planned depletion and represents a major change in direction entailing significant implementation costs. Agricultural interests, seeking to protect their irrigation rights, were influential in both the adoption and implementation processes. Considering the problems encountered, the immediate outlook for effective state management of ground water remains unfavorable. Future prospects, however, are more favorable. Oklahoma has developed an institutional structure capable of responding to changing priorities and needs of irrigators. This long‐run approach to ground‐water management matches the interests of the most relevant political constituency and may prove to be the most effective strategy.