bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reef and Nonreef Aquifers—A Comparison of Hydrogeology and Geochemistry, Northwestern Indiana
Authors: Schnoebelen Douglas J. , Krothe Noel C. 
Published: August 2005

AbstractThe principal bedrock aquifer system across much of Indiana consists of carbonate rocks of Silurian and Devonian age. The Silurian‐Devonian aquifer system is used extensively for irrigation in northwestern Indiana and is approximately 170 m thick. Reef and nonreef carbonate aquifers in northwestern Indiana were assessed using hydrogeology (lithology, geophysical logs, aquifer tests) and geochemistry (major ions and stable isotopes).The study showed differences in water quantity and quality between the reef and nonreef aquifers. The reef aquifer had few shales, abundant fossiliferous material (up to 100 m thick), and high porosities (10 to 15%). The nonreef aquifer had abundant shales, less fossiliferous material (a few meters thick), and low porosities. Total transmissivities at the reef sites were 697 m2/d, (meters squared per day) and 4831 m2/d, compared to 46 m2/d at the nonreef site. Flowpaths in the nonreef aquifer were associated with fractures and poorly connected moldic porosity with larger fractures and better connected vuggy porosity in the reef aquifer. Water chemistry data for the nonreef aquifer showed mean concentrations of sodium (235 mg/L [milligrams per liter]), sulfate (160 mg/L), sul‐fide (13 mg/L), fluoride (2.7 mg/L), and dissolved solids (635 mg/L) approximately two to five times larger when compared to mean concentrations in the reef aquifer. Ground water at the nonreef site was classified as a sodium‐bicarbonate type while that at the reef sites was calcium‐magnesium bicarbonate. The oxygen/deuterium isotope data indicates recharge from modern precipitation and not Pleistocene‐age recharge.
Cost Enectiveness of Well Site Selection Methods in a Fractured Aquifer
Authors: Taylor Kendrick C. , Minor Timothy B. , Chesley Matthew M. , Matanawi Korblaah 
Published: August 2005

AbstractIn regions where ground water flow is restricted to sparse, narrow fractures, productive and nonproductive drilling sites frequently are separated by only a few tens of meters. Drilling success rates are low in these areas because favorable drilling sites occur infrequently and are difficult to identify. The drilling success rate can be increased when imagery and surface geophysics are incorporated into the site selection method. We present a method to evaluate the economic benefit of various site selection methods and show that the use of surface geophysics and aerial photography can reduce drilling costs by approximately a factor of two in an area with a low drilling success rate that is characterized by narrow fracture zones covered with several meters of weathered clays and thick vegetation. The benefits are smaller and less certain when social considerations are a strong factor in site selection.
Rethinking Poisson‐Based Statistics for Ground Water Quality Monitoring
Authors: Loftis Jim C. , Iyer Hariharan K. , Baker Heather J. 
Published: August 2005

AbstractBoth the U.S. Environmental Protection Agency (EPA) and the American Society for Testing and Materials (ASTM) provide guidance for selecting statistical procedures for ground water detection monitoring at Resource Conservation and Recovery Act (RCRA) solid and hazardous waste facilities. The procedures recommended for dealing with large numbers of nondetects, as may often be found in data for volatile organic compounds (VOCs), include, but are not limited to, Poisson prediction limits (in both the EPA guidance and ASTM standard) and Poisson tolerance limits (EPA guidance only). However, many of the proposed applications of the Poisson model are inappropriate. The development and application of the Poisson‐based methods are explored for two types of data, counts of analytical hits and actual concentration measurements. Each of these two applications is explored along two lines of reasoning, a first‐principles argument and a simple empirical fit.The application of Poisson‐based methods to counts of analytical hits, including simultaneous consideration of multiple VOCs, appears to have merit from both a first principles and an empirical standpoint. On the other hand, the Poisson distribution is not appropriate for modeling concentration data, primarily because the variance of the distribution does not scale appropriately with changing units of measurement. Tolerance and prediction limits based on the Poisson distribution are not scale invariant. By changing the units of observation in example problems drawn from EPA guidance, use of the Poisson‐based tolerance and prediction limits can result in significant errors. In short, neither the Poisson distribution nor associated tolerance or prediction limits should be used with concentration data. EPA guidance does present, however, other, more appropriate, methods for dealing with concentration data in which the number of nondetects is large. These include nonparametric tolerance and prediction limits and a test of proportions based on the binomial distribution.
Bicarbonate, Sulfate, and Chloride Water in a Shallow, Clastic‐Dominated Coastal Flow System, Argentina
Authors: Logan William S. , Auge Miguel P. , Panarello Héctor O. 
Published: August 2005

AbstractMost of the cities southeast of Buenos Aires, Argentina, depend heavily on ground water for water supply. Whereas ground water quality is generally good in the region, economic development along the coastal plain has been constrained by high salinities.Fifty‐four wells were sampled for major ions in zones of recharge, transport and discharge in an area near La Plata, 50 km southeast of Buenos Aires. The shallow, southwest to northeast coastal flow system is >30 km long but is only 50 to 80 m thick. It consists of Plio‐Pleistocene fluvial sand overlain by Pleistocene eolian and fluvial silt and Holocene estuarine silty clay.Hydrochemical endmembers include HCO3, SO4, and Cl water. Bicarbonate‐type water includes high plain recharge water (Ca‐Na‐HCO3) that evolves through cation exchange and calcite dissolution to a high pH, pure Na‐HCO3 endmember at the southwest edge of the coastal plain. Similar Na‐HCO3 water is also found underlying recharge areas of the central coastal plain, and a lens of Ca‐HCO3 water is associated with a ridge of shell debris parallel to the coast.Mixed cation‐Cl water near the coastline represents intruded sea water that has undergone cation exchange. Chemically similar water underlying the southwest coastal plain, however, can be shown isotopically to have formed from fairly dilute solutions concentrated many times by evapotranspiration.In the central coastal plain, Na‐SO4‐Cl water (up to 17,000 mg/L SO4) underlies hummocks and, at depth, forms plumes in the subsurface. The chemical controls are dissolution of gypsum precipitated during pyrite oxidation, evapotranspiration, and calcite precipitation.This extreme diversity of water chemistry in a shallow, clastic flow system is uncommon. It is made possible by (1) the presence of oxidized, originally pyritic, but slightly permeable sediments that have been exposed to evolving geochemical and hydro‐dynamic conditions, and (2) highly focused recharge that favors the development of fresh water bodies underlying recharge zones and stagnant, evaporated water underlying other areas.
Evaluation of Electromagnetic Induction as a Reconnaissance Technique to Characterize Unsaturated Flow in an Arid Setting
Authors: Scanlon Bridget R. , Paine Jeffrey G. , Goldsmith Richard S. 
Published: August 2005

AbstractThe use of apparent electrical conductivity (ECa) measured with electromagnetic (EM) induction was examined as a reconnaissance tool for characterizing unsaturated flow in a semiarid region in the Chihuahuan Desert of Texas. Aboveground conductivity meters (EM31 and EM38) were used to measure ECa along transects in various geomorphic settings. Eight boreholes were drilled at different locations along the transects, and a downhole conductivity meter (EM39) was used to measure ECa. Samples were collected for analysis of clay, water, and chloride content to evaluate factors affecting spatial variability in ECa. Variations in ECa measured with the aboveground EM31 meter were affected by variations in clay content in a playa/interplaya setting, water content in a fissure, and chloride content adjacent to a drainage system. These factors affecting ECa were confirmed by comparing ECa measured with the downhole EM39 meter and clay, water, and chloride content of soil samples from boreholes. The hydrologic significance of parameters controlling ECa was evaluated. Variations in clay content are not hydrologically significant in this basin. High correlations between ECa and water content are difficult to interpret because in some areas water content variations simply reflect variations in clay content, as in the playa/interplaya setting, whereas in other areas higher water contents reflect higher water flux, as in the fissure. In some areas water content was below threshold values; therefore, ECa did not respond to water content or salinity in these areas. Although EM induction alone cannot distinguish causes of ECa changes, it provides a valuable tool for delineating variations in ECa that can be used to guide borehole locations and to provide valuable information for interpolating and extrapolating from point estimates provided by borehole data.
Boulton's Delayed Yield: A Different Context
Authors: Narasimhan T.N. 
Published: August 2005

AbstractIn 1954, Boulton proposed a delayed yield idealization to account for the dynamic contribution of water from the zone of desaturation during a pumping test in an unconfined aquifer. During the 1970s, the reasonableness of this idealization was questioned by some on the grounds that the exponential function with a constant parameter, used by Boulton to quantify the drainage process, was too simplistic and that the parameter will, in actuality, vary in time and space. Rather than discussing the merit of the delayed yield idealization in regard to an unconfined aquifer, the present work explores a different physical situation of an aquifer in which Boulton's idealization is realistic. Laboratory evidence exists to suggest that the deformation behavior of some aquifer materials is time dependent (creep or strain accumulation). In turn, this time dependence of deformation leads to a time dependence of the compressibility of the aquifer material, and hence, a time dependence of the aquifer's specific storage. In situations where the specific storage of an aquifer may be characterized by such time dependence, and if such time dependence can be reasonably approximated by an exponential function, then the response of such an aquifer to a constant rate pumping test will be described accurately by Boulton's mathematical formulation.
Spatial and Temporal Variability of Hydraulic Conductivity in Active Reattachment Bars of the Colorado River, Grand Canyon
Authors: Springer Abraham E. , Petroutson William D. , Semmens Betsy A. 
Published: August 2005

AbstractGround water/surface water interaction in rivers is dependent on the hydraulic conductivity of sediments lining the streambed. This study was designed to determine the temporal and spatial variability of the hydraulic conductivity of active sedimentary deposits lining the streambed of the Colorado River in the Grand Canyon. These reattachment bars form aquifers and create return‐current channels that are critical for supporting terrestrial and aquatic ecosystems. Monitoring wells were placed in five separate reattachment bars over a 200 mile long reach of the Colorado River below Glen Canyon Dam. Hydraulic conductivity was measured in all wells with the pneumatic slug test method. There is no significant difference in hydraulic conductivity among the five reattachment bars in the Grand Canyon. Hydraulic conductivity is bimodally distributed within a reattachment bar because of differing sizes of sediments deposited under different eddy velocities. A major controlled release of water from Glen Canyon Dam in March 1996 redistributed the sediments in the reattachment bars and compressed sediments deposited during previous floods. Hydraulic conductivity was significantly lower in these sediments after the flood due to the increased effective stress from the newly deposited sediment. A year later, after the sediments had drained and some deflation had occurred, hydraulic conductivity of sand deposits returned to values similar to pre‐flood values, whereas fine‐grained sediments that compressed weren't able to elastically respond.
Characterization of a Ground Water Hydrochemical System Through Multivariate Analysis: Clustering into Ground Water Zones
Authors: Suk Heejun , Lee Kang‐Kun 
Published: August 2005

AbstractMultivariate data analyses were performed with the hydrochemical data from a small area in Incheon, Korea. Previous studies based on hydrogeological and hydrochemical observations proposed that the ground water hydrochemical system of the site is governed by two distinct hydrochemical regimes. Each of the two regimes governs a ground water zone, zones A and B. The ground water in zone A is characterized by confined aquifer conditions and low values of dissolved oxygen (DO), NO3−, SO42+, Na+, Cl−, and Mg2+, without much seasonal fluctuation in chemical properties. On the other hand, the ground water in zone B is characterized by unconfined aquifer conditions, relatively higher DO and NO3−, and higher, but seasonally variable, Na+ and Cl−. The hydrochemical data used for the interpretation of the previous studies are employed for factor and cluster analysis. Major factors are interpreted as correlates of chemical processes. Factor scores are computed and the cluster analysis is performed using factor scores. The zones discretized from the cluster analysis have the same distribution pattern as the zones delineated in the previous studies. The factor scores and the cluster analysis results also imply seasonal variation of the ground water hydrochemical system.
Fluorescent Dye and Media Properties Affecting Sorption and Tracer Selection
Authors: Kasnavia Torez , Vu De , Sabatini David A. 
Published: August 2005

AbstractThis paper discusses the importance of fluorescent dye sorption when selecting dyes for tracer studies. The effect of dye and media properties on dye sorption was evaluated using four fluorescent dyes (fluorescein, rhodamine B, rhodamine WT, and sul‐forhodamine B), two oppositely charged mineral surfaces (alumina and silica), and n‐octanol (as a neutral organic phase). Fluorescein, which has only negative functional groups, sorbed least onto negatively charged silica but most onto positively charged alumina. The rhodamine dyes, with a permanent positive charge and negatively charged functional groups, sorbed onto both alumina and silica. Sulforhodamine B, with two strongly electronegative sulfonic groups, sorbed less onto negatively charged silica than did rhodamine WT, which has two carboxyl groups. Dye partitioning into n‐octanol was strongly pH dependent with fluorescein being the most hydrophobic, followed by rhodamine WT and sulforhodamine B. Since fluorescent dyes are subject to sorption, dye selection should be based on their chemical properties, media characteristics, and laboratory batch and column studies.
Transport and Attenuation of Carboxylate‐Modified Latex Microspheres in Fractured Rock Laboratory and Field Tracer Tests
Authors: Becker Matthew W. , Reimus Paul W. , Vilks Peter 
Published: August 2005

AbstractUnderstanding colloid transport in ground water is essential to assessing the migration of colloid‐size contaminants, the facilitation of dissolved contaminant transport by colloids, in situ bioremediation, and the health risks of pathogen contamination in drinking water wells. Much has been learned through laboratory and field‐scale colloid tracer tests, but progress has been hampered by a lack of consistent tracer testing methodology at different scales and fluid velocities. This paper presents laboratory and field tracer tests in fractured rock that use the same type of colloid tracer over an almost three orders‐of‐magnitude range in scale and fluid velocity. Fluorescently‐dyed carboxylate‐modified latex (CML) microspheres (0.19 to 0.98 μm diameter) were used as tracers in (1) a naturally fractured tuff sample, (2) a large block of naturally fractured granite, (3) a fractured granite field site, and (4) another fractured granite/schist field site. In all cases, the mean transport time of the microspheres was shorter than the solutes, regardless of detection limit. In all but the smallest scale test, only a fraction of the injected microsphere mass was recovered, with the smaller microspheres being recovered to a greater extent than the larger microspheres. Using existing theory, we hypothesize that the observed microsphere early arrival was due to volume exclusion and attenuation was due to aggregation and/or settling during transport. In most tests, microspheres were detected using flow cytometry, which proved to be an excellent method of analysis. CML microspheres appear to be useful tracers for fractured rock in forced gradient and short‐term natural gradient tests, but longer residence times may result in small microsphere recoveries.
Hydrochemical Approach to the Alterations of the Recharge of a Karst Aquifer Consecutive to a Long Pumping Period: Example Taken from Pinchinade Graben (Mouans‐Sartoux, French Riviera)
Authors: Reynaud A. , Guglielmi Y. , Mudry J. , Mangan C. 
Published: August 2005

AbstractThe carbonate aquifer of the Pinchinade graben, which has a well‐delimited geometry, involves water with well‐defined chemical types from calcium sulfate to magnesium bicarbonate. Each ground water type corresponds to a well‐delimited area of the aquifer: the magnesium bicarbonate for the Liassic and Rhetian limestone water (with 10 to 30 mg L‐1 of sulfate) and calcium sulfate for the water of the relatively impermeable layer of the underlying Keuper (with 300 to 1500 mg L−1 of sulfate). A four‐year pumping test with a bimonthly to daily monitoring of water chemistry has allowed evaluation of the renewal of the exploitable water reserve. During the four‐year period, the survey shows that the average discharge is balanced by natural recharge (2.8 to 105 m3 y−1). A change in the chemical character of the water was observed from Rhetian to Keuper type (from 35 to 167 mg L−1 of sulfate). Such a change indicates a progressive exhaustion of the Rhetian reserves, which are the greater part of the exploitable reserve in the area. The same phenomenon is observed daily depending on the pumped discharge and the season. For pumping rates below 26 m3 h−1, the borehole drains the Rehetian inflows to a degree depending on high or low water levels. For pumping rates above 26 m3 h−1, whatever the period, the permeable Keuper layers are pumped and sulfate peaks ensue.
Development of a Comprehensive Watershed Model Applied to Study Stream Yield under Drought Conditions
Authors: Perkins Samuel P. , Sophocleous Marios 
Published: August 2005

AbstractWe developed a model code to simulate a watershed's hydrology and the hydraulic response of an interconnected stream‐aquifer system, and applied the model code to the Lower Republican River Basin in Kansas. The model code links two well‐known computer programs: MODFLOW (modular 3‐D flow model), which simulates ground water flow and stream‐aquifer interaction; and SWAT (soil water assessment tool), a soil water budget simulator for an agricultural watershed. SWAT represents a basin as a collection of subbasins in terms of soil, land use, and weather data, and simulates each subbasin on a daily basis to determine runoff, percolation, evaporation, irrigation, pond seepage, and crop growth. Because SWAT applies a lumped hydrologic model to each sub‐basin, spatial heterogeneities with respect to factors such as soil type and land use are not resolved geographically, but can instead be represented statistically. For the Republican River Basin model, each combination of six soil types and three land uses, referred to as a hydrologic response unit (HRU), was simulated with a separate execution of SWAT. A spatially weighted average was then taken over these results for each hydrologic flux and time step by a separate program, SWBAVG. We wrote a package for MODFLOW to associate each subbasin with a subset of aquifer grid cells and stream reaches, and to distribute the hydrologic fluxes given for each subbasin by SWAT and SWBAVG over MODFLOW's stream‐aquifer grid to represent tributary flow, surface and ground water diversions, ground water recharge, and evapotranspiration from ground water. The Lower Republican River Basin model was calibrated with respect to measured ground water levels, streamflow, and reported irrigation water use. The model was used to examine the relative contributions of stream yield components and the impact on stream yield and base flow of administrative measures to restrict irrigation water use during droughts. Model results indicate that tributary flow is the dominant component of stream yield and that reduction of irrigation water use produces a corresponding increase in base flow and stream yield. However, the increase in stream yield resulting from reduced water use does not appear to be of sufficient magnitude to restore minimum desirable streamflows.
Enhancements for Passive Vapor Extraction: The Hanford Study
Authors: Ellerd Michael G. , Massmann Joel W. , Schwaegler Daniel P. , Rohay Virginia J. 
Published: August 2005

AbstractPassive vapor extraction involves wells that are screened in the unsaturated zone and open to the atmosphere. Gas will flow out of the subsurface through the open well during periods of low barometric pressure. Field and modeling studies have been completed to evaluate enhancements for a passive vapor extraction system at a site contaminated with carbon tetrachloride on the Hanford nuclear reservation near Richland, Washington. During a 38‐hour period of low barometric pressure, approximately 500 m3 of air were vented from the subsurface. Approximately 27 grams of carbon tetrachloride were removed from the subsurface during this same outflow event. On an annual basis, more than 15 kilograms of carbon tetrachloride have been removed from each of several passive extraction wells. Computer simulations based on the field data indicate that surface covers smaller than 30 m radius will result in relatively small enhancements of flow. However, with larger surface seals (i.e., up to 90 m radius), volumetric flow rates more than doubled. Simulations showed that check valves might increase the rate at which subsurface gases are extracted by a factor of nearly three. These estimates are sensitive to dispersion coefficients. If not properly designed, filters used to treat effluent gases from passive extraction systems can significantly reduce the effectiveness of these systems.