bluuebunny/crossref_metadata_2025 huggingface dataset:
HYDROLOGIC TEST SYSTEM FOR FRACTURE FLOW STUDIES IN CRYSTALLINE ROCK
Authors: Raber E. , Lord D. E. , Burklund P. W.
Published: March 2006

Abstract. A hydrologic test system has been designed to measure the intrinsic permeabilities of individual fractures in crystalline rock. This report contains the design schematics and specifications necessary to build and/or modify this test system for other similar field applications. This system is used to conduct constant pressure/declining flow rate and pressure pulse hydraulic tests. The system is composed of four distinct units: (1) The Packer System, (2) Injection System, (3) Collection System, and (4) Electronic Data Acquisition System. The apparatus is built in modules so it can be easily transported and reassembled. It is also designed to operate over a wide range of pressures (0–300 psig) and flow rates (0.2–1.0 gal/min). This system has proved extremely effective and versatile in its use at the Climax Facility, Nevada Test Site.
Results of Seepage Meter and Mini‐Piezometer Study, Lake Mead, Nevada
Authors: Woessner William W. , Sullivan Kevin E.
Published: March 2006

The seepage meter and the mini‐piezometer were utilized in an attempt to evaluate ground‐water reservoir interactions over a 12‐month period at Echo Bay in Lake Mead. In conjunction with these techniques three standard piezometers, refraction seismic data, and water chemistry data were utilized to interpret seepage device results. During a four‐month period, from December 1979 to March 1980, an 8 ft (2.5 m) rise in reservoir stage, the reservoir contributed water to Echo Wash bank storage at rates of up to 0.29 gpd/ft2 (12 lpd/m2). Ground‐water discharge occurred for the remainder of the project, during a stage decline from April 1980 to May 1980, a rise in June 1980, and leveling off and slight decline for the remainder of the year, July 1980 to December 1980. The maximum seepage meter ground‐water discharge rate of 3.0 gpd/ft2 (122 lpd/m2) was recorded in December 1980. Seepage meter water chemistry data for June were similar to Lake Mead water chemistry and were interpreted to be previously recharged Lake Mead water. September water chemistry data showed two possible components of ground‐water discharge, a high SpC calcium sulfate Echo Wash ground water and a lower SpC Lake Mead recharged bank storage water. December ground‐water chemistry data showed discharge to be a high SpC calcium sulfate water similar to Echo Wash ground‐water quality which was apparently unaffected by Lake Mead inflow. Mini‐piezometer data were collected at each seepage meter site. However, these data usually did not provide correlative results with seepage meter data probably because of suspended sediment in the piezometer water column and plugging of the perforated tip. Seepage meters were successfully utilized to characterize reservoir ground‐water interaction in Echo Bay.
Weighting of Observed Heads for the Inverse Problem
Authors: Ross Benjamin
Published: March 2006

In using least‐squares parameter estimation techniques to solve for hydrogeologic parameters, one may use a weighting function to reflect differing reliabilities of head measurements. In studies published to date, the weighting function has been used in an ad boc manner or not at all. The inverse square of the observed hydraulic gradient, adjusted to reflect the modeler's perception of geologic heterogeneity and data reliability, is typically an appropriate weighting function.
Determination of the Hydrogeologic Properties of Lakebeds Using Offshore Geophysical Surveys
Authors: Bradbury Kenneth R. , Taylor Robert W.
Published: March 2006

Studies of the relationships between ground‐water systems and surface‐water systems (lakes) generally require knowledge of the hydrogeologic properties of lakebed materials. Direct measurement of these properties may be prohibitively expensive or difficult in an offshore environment. A correlation between longitudinal conductance, a geoelectric parameter, and lakebed leakance (vertical hydraulic conductivity divided by thickness) may provide a rapid and inexpensive method for estimating lakebed hydrogeological properties using data collected by offshore seismic and electrical surveys. A test of the method at three study sites in Lake Michigan shows a positive linear relationship between the logarithm of longitudinal conductance and the logarithm of lakebed leakance at the three sites.
Aquifer Classification for the UIC Program: Prototype Studies in New Mexico
Authors: Wilson Lee , Holland Michael T.
Published: March 2006

Three case studies from New Mexico illustrate methods by which aquifers can be classified for purposes of the Federal Underground Injection Control program. The principal technique involves preparation of hydrogeologic maps or cross sections which display information on the permeability of rock units and the dissolved solids content of formation fluids. Because deep water wells are lacking in most areas, the analysis normally requires considerable interpretation of geological and geophysical logs collected by energy and mineral companies, plus use of a general model or concept about regional hydrogeology. Injection of waste fluids into aquifers containing water with less than 10,000 mg/1 dissolved solids is not allowed unless an exemption is justified by economic, engineering and other factors. Based on the case studies, regulatory exemptions will be possible for aquifers which are hydrocarbon or mineral‐producing, or which are important for brine disposal purposes.
Role of Geological and Geophysical Data in Modeling a Southwestern Alluvial Basin
Authors: O'Brien Keith M. , Stone William J.
Published: March 2006

A parameter‐estimation technique based on existing hydrological, geophysical, and geological data was developed to approximate transmissivity values for use in a ground‐water flow model of the Animas Valley, southwest New Mexico. Complete Bouguer gravity anomaly maps together with seismic‐refraction profiles, geologic maps, geologic, geophysical, and drillers' logs, water levels, and pumping‐test data provide insight into the transmissivity of bolson deposits throughout the basin.

The transmissivity distribution was primarily based on reported pumping and specific‐capacity tests in conjunction with complete Bouguer gravity anomaly maps and well log data. Reported transmissivity values were characterized by gravity values and well log data. In grid blocks lacking pumping and specific‐capacity tests, transmissivity values were assigned based on the relationship of gravity values and well log data within the grid block to gravity values and well log data within other grid blocks for which transmissivity values are available.

A two‐dimensional, finite‐difference, ground‐water flow computer code was used to evaluate the effectiveness of the parameter‐estimation technique. Although the trial‐and‐error method of calibration was employed, the actual computer time necessary for model calibration was minimal. The conceptually straightforward approach for parameter estimation utilizing existing hydrological, geophysical, and geological data provides realistic parameter estimates.
Thermal Impact of Residential Ground‐Water Heat Pumps
Authors: Warner Don L. , Algan Ugur
Published: March 2006

A computer simulation study was conducted to quantify the potential thermal impact of residential water‐source heat pump usage on ground‐water aquifers.

In a first phase of the study, weather data for nine locations throughout the country were used to estimate the energy requirements for heating and air conditioning a typical residence. These energy requirements were then translated into the volumetric water demands for a selected heat pump at each location. A representative model aquifer was then defined and its characteristics used, along with the heat pump water requirements and design ΔT's (difference between inlet and outlet water temperature) to identify the important parameters that contribute to heat transfer and to model the movement of the thermal front resulting from injection of heat pump discharge water at the nine locations.

The major factor that determines the heat pump thermal impact was found to be the net amount of heat injected into, or removed from an aquifer. Other significant factors included well design, heat pump design ΔT, and physical properties of the aquifer such as thickness, porosity and dispersivity.

The study showed that, in climates where winter heating demand is very nearly equal to summer cooling demands, the injection of heat pump discharge water did not cause any significant modification of the ambient model aquifer temperature. However, in hot or cold climates where air conditioning or heating demand dominates, measurable thermal changes occurred in the model aquifer. In most cases, the maximum temperature
The Investigation of Aquifer Parameters Using Multiple Piezometers
Authors: Walthall S. , Lngram J. A.
Published: March 2006

In order to investigate the aquifer parameters of a fissured layered sandstone aquifer, it was found necessary to construct and test an abstraction borehole using laboratory, double packer, geophysical and pumping test techniques. Good correlation was found between the techniques when the aquifer was represented by a fissured layered aquifer with low permeability bands separating layers of higher permeability. The use of multiple piezometers proved to be the only way of obtaining sensible results for field pumping tests and has given storage coefficients for both the confined and unconfined sections of the aquifer.
Impact of Land Use on Ground‐Water Quality in Southern Delawarea
Authors: Ritter William F. , Chirnside Anastasia E. M.
Published: March 2006

A ground‐water quality monitoring study was conducted in Kent and Sussex Counties, Delaware. In the coastal region of Sussex County, 210 wells were sampled 12 times each. In noncoastal Sussex and Kent Counties, 272 wells were sampled once each season over a period of one year. Over 99 percent of the wells were in the water‐table aquifer.

In coastal Sussex County, 32% of the wells had average nitrate concentrations above the EPA drinking‐water standard of 10 mg/1 N. In noncoastal Sussex County and Kent County, 21% and 8% of the wells respectively, had nitrate concentrations above 10 mg/1. The highest nitrate concentrations occurred in areas with intensive broiler production or intensive crop production with excessively‐drained soils. Nitrate concentrations in forest areas were <1.5 mg/1. Poultry manure, septic tanks and fertilizers all contributed to the high nitrate concentrations. Poultry manure was one of the major causes of nitrate contamination in four out of the five top prioritized ground‐water problem areas.

Bacteria contamination was low in all sampling areas. Lead, cadmium and chromium were far below drinking‐water standards in all but a few wells.
Remote Sensing and Geophysical Investigations of Glacial Buried Valleys in Northeastern Kansas
Authors: Denne Jane E. , Yarger Harold L. , Macfarlane P. Allen , Knapp Ralph W. , Sophocleous Marios A. , Lucas James R. , Steeples Don W.
Published: March 2006

Aquifers found in glacial buried valleys are a major source of good‐quality ground water in northeastern Kansas. The extent and character of many of these deposits are not precisely known, so a detailed study of the buried valleys was undertaken. Test drilling, Landsat imagery, shallow‐earth temperature measurements, seismic refraction, surface electrical resistivity, and gravity data were used to evaluate two sites in Nemaha and Jefferson Counties. Tonal patterns on springtime Landsat imagery and winter/summer anomalies in shallow‐earth temperatures were quick and inexpensive methods for locating some glacial buried aquifers and suggested areas for more intensive field studies. Reversed seismic refraction and resistivity surveys were generally reliable indicators of the presence or absence of glacial buried valleys, with most depth determinations being within 25% of test‐drilling results. The effectiveness of expensive test‐hole drilling was greatly increased by integrating remote sensing, shallow‐earth temperature, seismic, and resistivity techniques in the two buried valley test areas. A gravity profile allowed precise definition of the extent of one of the channels after the other techniques had been used for general information.
Ground‐Water Mounding Beneath a Large Leaching Bed
Authors: Chan H. T. , Sykes J. F.
Published: March 2006

An 84 m (276 ft) by 64 m (205 ft) experimental leaching bed was constructed to receive the secondary effluent from the Norwood, Ontario sewage treatment plant. The distribution system consisted of 100 mm diameter perforated pipes laid 2.1 m apart in 0.45 m wide trenches. The main soil layer at the test site was sandy silt. Ground‐water levels at the site were measured approximately weekly at 36 piezometers for a period of about 2½ years. An initial hydraulic loading of 122,700 1/day caused surface ponding. A reduced loading of 40,900 1/day was then used for most of the study period. Ground‐water level fluctuations beneath and adjacent to the leaching bed were attributed to seasonally varying infiltration and hydraulic loading. The experimental data were simulated using a transient two‐dimensional, phreatic integrated depth finite‐element model and an analytic solution for ground‐water mounding. Results from the study indicated that seasonal infiltration was a controlling factor in determining leaching bed design loads. Both mathematical models were found adequate for design.
The Hydrological Effects of Gravel Winning in an Area West of London, United Kingdom
Authors: Morgan‐Jones M. , Bennett S. , Kinsella J. V.
Published: March 2006

The ground‐water flow and ground‐water quality of extensive gravel deposits in the Lower Colne Valley, near London, England are described. The great demand for aggregates in southeast England over the past 30 years has resulted in extensive exploitation of these gravels, the worked‐out pits being either left water‐filled for recreational purposes, or filled with a variety of waste materials. Both after‐uses are shown to alter the ground‐water situation either by locally lowering or raising ground‐water levels, such effects having been described in both French and German literature, or by causing ground‐water and surface‐water pollution problems. If the scale of pit development or landfilling is large as in the Lower Colne Valley, then remedial measures have to be undertaken to minimize the pollution risk and to obviate problems caused by raised or lowered ground‐water levels.
Analysis of Conceptual Designs for Remedial Measures at Lipari Landfill, New Jersey
Authors: Andersen Peter F. , Faust Charles R. , Mercer James W.
Published: March 2006

During the two‐week period from March 12 through March 26, 1982, a preliminary conceptual design analysis on various remedial measures for the Lipari Landfill, New Jersey, was performed. This site is currently ranked at the top of the EPA's Superfund Cleanup List. This report demonstrates the practical benefits and limitations of applying models (both analytical and numerical) to a hazardous waste site in a restricted period of time. The numerical model was used to simulate current flow conditions at the site and provide initial conditions for a series of sensitivity simulations. These sensitivity simulations were designed to test (1) a slurry wall, (2) drain location, (3) drain depth, and (4) a clay cap. Analytical solutions were designed to analyze (1) water in place, (2) flow through an underlying layer, the lower Cohansey, (3) draining the lower Cohansey, (4) flushing the contaminated area using wells, and (5) convective arrival time of contaminants to drains. This analysis quantified discharge to drains, flow rates to a swamp downstream of the landfill, time required to drain the landfill, and contaminant travel times that would result from the implementation of each of the remedial measures that were suggested. The conclusions from this study were used by engineers and planners who incorporated, economics and engineering decisions for the various remedial measures considered.
Algorithm for Theis Solution
Authors: Gupta A. Das , Joshi S. G.
Published: March 2006

An algorithm for the Theis solution of pumping test data has been developed taking into account the basic principles of graphical approach of curve‐matching. The method is simple and does not need initial approximation of transmissivity and storativity as required by approaches suggested by Saleem (1970) and McElwee (1980). As a measure of error of fitting, integral square error is computed between the observed drawdown and drawdown calculated from the theoretical equation with the values of coefficients estimated by the procedure. Also root mean square deviation in drawdown is calculated. The algorithm is capable of identifying data with errors in observation or recording. The reliability of the algorithm and its limitations are discussed on the basis of test runs with synthetic data having varying magnitudes of error and varying distributions of error points in the data set. The estimates of parameters by the proposed algorithm for a typical field test data compare very well with the estimates by the sensitivity approach developed by McElwee (1980).
Contamination of Aquifers by Overpressuring the Annulus of Oil and Gas Wells
Authors: Harrison Samuel S.
Published: March 2006

Medina gas wells and oil wells in northwestern Pennsylvania, northeastern Ohio, and western New York create a potential for contamination of the fresh‐water aquifers that overlie the production zones of these wells. Most of these wells are constructed in a manner which results in an open annulus which is a few hundred to a few thousand feet long below the surface casing of the well. This annulus is a potential avenue of migration of contaminants from strata of higher hydrodynamic pressure into formations of lower hydrodynamic pressure. If gas from the strata exposed to the annulus is not permitted to escape to the atmosphere, the annulus may become pressurized, and a hydraulic gradient may be created between the potential contaminants in the annulus (e.g., brine and/or natural gas) and the overlying fresh‐water aquifers. If a permeability pathway exists between the pressurized annulus and an overlying fresh‐water aquifer, contamination of the aquifer will result.

The risk of contaminating fresh ground water with the contents of a gas‐ or oil‐well annulus could be greatly reduced by filling the annulus with cement. An alternative precaution would be to operate the well in a manner that does not allow the annulus pressure to exceed the normal pressure of the formations exposed to the annulus.
Performance and Analysis of Drillstem Tests in Small‐Diameter Boreholes
Authors: Marinelli Fred , Rowe Jerry W.
Published: March 2006

While drillstem tests have been used extensively in the petroleum industry to obtain reliable measurements of hydraulic parameters in single boreholes, the technique has been used only to a limited extent in ground‐water investigations. This is due in part to the limited availability and high cost of suitable equipment for small‐diameter boreholes. In this study, drillstem tests were performed in exploratory boreholes to evaluate the hydraulic characteristics of a proposed compressed air energy storage site in central Illinois. The tests were conducted in small‐diameter coreholes (vertical and inclined) at depths up to 610 meters (2000 ft) using a drillstem tool designed and field‐tested by the authors. Field data were analyzed using semilog and curve‐matching techniques. Values of hydraulic conductivity obtained by the two methods were generally in very good agreement. The curve‐matching method allowed for calculation of wellbore storage and an estimation of well‐bore damage (skin effect). Test results indicate that exploratory boreholes were severely damaged by the coring process. In the presence of wellbore damage, slug test hydraulic conductivities were significantly lower than those given by drillstem tests conducted in the same zones. The sole use of slug tests would have underestimated hydraulic conductivity and led to erroneous conclusions regarding site conditions. The drillstem test methodology described herein offers a cost‐effective technique for measuring representative values of hydraulic conductivity in single boreholes.
Characterization of Dye Tracer Plumes: In Situ Field Experiments
Authors: Naymik Thomas G. , Sievers Mark E.
Published: March 2006

The second ground‐water dye tracer experiment at Sand Ridge State Forest, Illinois, was conducted during the Spring of 1983. Slugs of three different fluorescent dyes (Rhodamine WT, Amino G Acid, and Lissamine FF) were allowed to migrate under natural hydraulic gradient conditions through a water‐table aquifer composed of wind‐blown sand overlaying glacial outwash sand and gravel. The plumes in the outwash deposit and in the dune sand were monitored first by a line of sand point wells placed perpendicular to flow at a distance of 10 ft and 5 ft, respectively, from the source wells. A trilevel nest of sand points was then placed in the path of each plume at a greater distance (50 feet from the sources of the deep plumes). The field data suggest that the plume geometry varied with distance from the source. A solute transport model, calibrated to the field data, provided estimates of longitudinal dispersivity (0.10 ft and 0.17 ft for the plumes in the lower unit) and average linear velocity (approximately 1.5 and 1.7 ft/day in the lower unit and 0.21 ft/day in the upper unit). The model was then used as a mass accounting system to relate the tracer concentrations detected in monitoring wells to the mass within the plumes.
Waste‐Water Injection: Geochemical and Biogeochemical Clogging Processes
Authors: Oberdorfer June A. , Peterson Frank L.
Published: March 2006

Examination of near‐well clogging processes at two experimental injection sites in Hawaii shows that filtration of suspended solids is not a long‐term cause of clogging. While particulate filtration is probably a short‐term cause of clogging at the start‐up of injection, the injected organics are biodegraded once the microbial biomass becomes established. The injection head gradient determined from monitoring wells shows that most of the initial head loss is immediately adjacent to the well, but that after several weeks it shifts to a region over 0.5 m from the well. Denitrifying bacteria become sufficiently numerous to produce significant amounts of nitrogen gas, which in turn produces a gas‐bound zone about 0.5 to 1 m from the well. With continued injection the nitrogen gas‐bound zone is slowly extended farther out into the injection stratum. Dissolution of the carbonate aquifer also occurs, but its effects are partially masked by gas binding.
Estimating Aquifer Permeability from Formation Resistivity Factors
Authors: Kwader Thomas
Published: March 2006

A comparison of permeability results for individual producing zones obtained from pumping tests and flow‐meter logs showed a good correlation to calculated corresponding formation resistivity factors (F). Where F = a/Øm or F = R0/RW, and porosity (Ø) is obtained from the neutron log, m is the formation cementation factor, Ro is saturated formation resistivity from normal electric logs, and Rw is formation pore‐water resistivity. Unlike formations containing saline water where the electrical current is conducted through the pore fluid, in fresh‐water aquifers the electrical current appears to be conducted along the grain‐aqueous interface by surface conductance rather than through the grain or pore fluid. Surface conductance of the current serves to increase the current path length which is recorded as an increase in the measured saturated resistivity (Ro). The current path direction and length through the formation is directly related to the shape, diameter, and sorting of the grains, geometric packing arrangement, and degree of matrix cementation. Fortunately, all of these factors that serve to increase the current path [which in turn directly increase saturated formation resistivity (Ro) and F] also are factors that increase formation permeability.

Relative changes in F values can be matched with known permeabilities from aquifer tests and flowmeter logs to quantify the relative productivity of the various zones analyzed. Once this relationship is established, F values can be used to assign relative permeabilities within a single borehole or from borehole to borehole for a given geographical area.

This method has been successfully used to estimate permeability in both unconsolidated sands and Tertiary carbonate aquifers in the southeastern Coastal Plain of the United States.
Role of Volcanic Tuffs in Ground‐Water Regime of Valle Central, Costa Rica
Authors: Foster Stephen S. D. , Ellis Ann T. , Losilla‐Penon Marcelino , Rodriguez‐Estrada Hugo V.
Published: March 2006

Laboratory and field testing programs on the hydraulic properties of volcanic rocks from the Valle Central of Costa Rica in Central America have been undertaken. This area is typical of much of the circum‐Pacific volcanic belt. Most of the tuffaceous deposits are shown to have exceptionally high effective porosity (45‐65%), moderate hydraulic conductivity (0.02‐0.5 m/d) and very broad pore‐size distributions. Rather unexpectedly, they provide the major element of regulating storage in the overall ground‐water regime.
Ground‐Water Contamination and Well Construction in Southeast Nebraska
Authors: Exner Mary E. , Spalding Roy F.
Published: March 2006

Nitrate‐nitrogen (NO3‐N) concentrations and total (TC) and fecal coliform (FC) densities were determined in ground water from 268 household and stock wells in an 1100 mi2 area of southeast Nebraska. Seventy‐one percent of the samples had NO3‐N concentrations above 10 mg/1 and/or TC densities ≥ 1/100 ml. Most of the NO3‐N contamination is from the dissolution of manure in barnyards and corrals. The average δ15N value was + 11.9%0 for the 115 samples with NO3‐N levels in excess of 8.5 mg/1.

Only 10% of the wells met Nebraska's criteria for private well construction. NO3‐N levels exceeded 10 mg/1 in 4% of these wells while 30% contained one or more TC/100 ml. The highest incidence of NO3‐N and coliform contamination occurred in dug or augered wells with open‐jointed casing. The rates were 47% and 80%, respectively.

Low levels of atrazine were detected only in the poorly constructed wells. One well contained alachlor.
Brackish Water in Unsaturated Confining Beds at a Texas Lignite Minea
Authors: Dutton Alan R.
Published: March 2006

Deposits of low permeability are hydrologic barriers between reclaimed land and juxtaposed aquifers and should limit the impact of mining on ground‐water quality. Clay‐stone and mudstone in argillaceous facies of the Calvert Bluff Formation (lower Eocene, Wilcox Group) function as confining beds in the East Texas Basin. In the subsurface and at the outcrop, water in argillaceous deposits is brackish to saline. Samples of vadose water from the outcrop of confining beds at the Big Brown lignite mine in Freestone County, Texas, have a chloride concentration of up to 3,500 mg/l and total dissolved solids of up to 8,000 mg/l. Ground‐water composition evolved from Eocene sea water by seven‐ to nine‐fold dilution with rain water. Ion exchange, pyrite oxidation, and calcite dissolution further modified water composition. The amount of recharge through the vadose zone where confining layers crop out is probably negligible over an extremely long time. Meteoric flushing in reclaimed land at the surface mine is many times greater than that in unmined mudstone deposits, and the chemical composition of vadose water in reclaimed land is changed by further dilution and water‐rock reactions.
Effect of Agricultural Land Use on Ground‐Water Quality in a Small Pennsylvania Watersheda
Authors: Pionke Harry B. , Urban James B.
Published: March 2006

Ground‐water quality, determined by 10 samplings of 14 wells within a 7.4 km2 watershed during 1973–1982, was related to land use and geology. The wells represent forest and cropland use associated with three geologic zones. Nitrates, chloride and phosphate concentrations were much higher in ground waters underlying cropland. The mean concentrations ranged from five to seven times those observed in ground water underlying forests. The contamination pattern is consistent with that computed from a nutrient balance, based on known fertilizer and manure use on local croplands. Downgradient from the primary agricultural area, a geologic zone exists through which ground water from agricultural sources must pass to reach the stream. In this zone, the nitrate, chloride, and phosphate concentrations are greatly decreased due to mixing and dilution. The chemical nature of these ground waters reflects more the geochemistry of local geologic deposits than the impact of cropland use.

A ground‐water flow system was hypothesized, based on known geologic, hydrologie, and geometric properties. The flow system is supported by the chemical data.
DISPERSION MODELING OF MULTIPLE SOURCES USING THE HP‐41CV
Authors: Allen Dan H.
Published: March 2006

Abstract. WMPLUME is an analytic dispersion model based on the Wilson and Miller equation presented here in a program for the HP‐41CV handheld, programmable calculator, the HP‐41CX, or the HP‐41C with four memory modules. The user specifies the spacing and extent of the field of observation points. The calculator can handle up to 36 fully penetrating, continuous injection well sources or a lesser number of discontinuous wells. The time of observation can be changed easily and sources can be added or deleted readily. The code is prepared for use with or without a printer attached to the calculator.
A GALERKIN FINITE‐ELEMENT PROGRAM FOR SIMULATING UNSATURATED FLOW IN POROUS MEDIA
Authors: Khaleel R. , Yeh T.‐C.
Published: March 2006

Abstract. A fully documented Galerkin finite‐element FORTRAN program is presented for solving the one‐dimensional, transient flow equation in unsaturated porous media. Material balance error summaries are presented to demonstrate accuracy of the numerical scheme. Comparison of our simulated results with other existing numerical solutions using the Galerkin scheme provided excellent agreement.
Fault Severed Aquifers Along the Perimeters of Wyoming Artesian Basins
Authors: Huntoon Peter W.
Published: March 2006

The mountain uplifts which border the major artesian basins of Wyoming are asymmetric antiforms bounded on one flank by large displacement Laramide thrust faults. These thrusts sever the hydraulic continuity of aquifers, thereby creating separate circulation systems in the hanging wall and foot wall blocks. Fault severing of the Paleozoic aquifers can be identified by (1) potentiometric discontinuities across the faults, (2) water quality contrasts across the faults, and (3) geothermally heated waters in the foot wall blocks.

Isolated but active circulation systems develop in the hanging wall blocks in which good permeabilities and good quality water prevail. In contrast the foot walls are generally characterized by poor permeabilities and poor water qualities.

Fault severing of the Paleozoic aquifers in the Wyoming foreland province is a significant factor because nearly half of the basin perimeters are fault severed. The result is that exploration for large‐volume, good‐quality supplies must focus on the hanging wall blocks in the fault severed environments.
Economic Aspects in the Investigation of Ground‐Water Contamination Episodes
Authors: Shechter Mordechai
Published: March 2006

The paper examines some economic aspects of ground‐water pollution, focusing on the exploitation of an aquifer as a source of drinking water. Using the contamination episode at Price Landfill, New Jersey, as a case study, it addresses analytical and information issues which characterize ground‐water pollution. Involved here are uncertainties associated with the environmental medium (especially knowledge of solute‐transport processes), and health risk assessment (principally dose‐response relationships). The field application employed two approaches to the modeling of the physical‐chemical processes to derive mortality risk estimates. These estimates in turn form the basis for preliminary assessment of expected damages: reduced longevity, and cost of control and remedial measures. The results are offered as an essential informational input for a benefit‐cost analysis of ground‐water protection and management policies.
Potentiometric Mapping from Incomplete Drill‐Stem Test Data: Palo Duro Basin Area, Texas and New Mexico
Authors: Bair E. Scott , O'Donnell Timothy P. , Picking Larry W.
Published: March 2006

Drill‐seem test (DST) data from wildcat wells and wells sponsored by the U.S. Department of Energy were used to construct pressure‐depth diagrams and regional potentiometric surfaces of the Wolf camp and Pennsylvanian aquifers. These deep‐basin aquifers represent the two regionally important downgradient aquifers that underlie the host rock at the proposed high‐level nuclear‐waste repository sites in the Palo Duro Basin area of Texas and New Mexico. More than 5,500 DSTs were screened and classified according to shut‐in pressure and shut‐in time criteria devised to evaluate the quality of the DST data and to delete dubious DST data. After screening, three sets of pressure‐depth diagrams and potentiometric‐surface maps were constructed, corresponding to three levels of data refinement.

The initial Wolfcamp and Pennsylvanian regional potentiometric surfaces contained several prominent local mounds and depressions with unrealistic variations in the direction and magnitude of hydraulic gradients. Pressure‐depth data and records and maps of historic oil and gas production showed that many DSTs were performed in depressured oil and/or gas production zones. The low shut‐in pressures recorded during these tests caused abnormally low heads to be calculated and contoured. Formation pressures recorded in these depressured zones represent local temporal pressures in a regional flow system that is probably steady state. Deletion of depressured DSTs produced regional potentiometric surfaces that were more realistic but contained a few large local mounds and depressions caused by local aberrant DST data. Deletion of local aberrant grossly underpressured DSTs not attributable to oil and/or gas production and local aberrant grossly overpressured DSTs, based on comparison of initial shut‐in pressures and heads in the same well and/or in adjacent wells at a similar depth in the same geologic unit, produced potentiometric surfaces that show regional and some local variations in flow directions and hydraulic gradients. Linear regression of the pressure‐depth data showed that most of the refinement in the data was due to culling depressured DSTs. Some additional refinement was due to culling local aberrant grossly underpressured and grossly overpressured DSTs.
A COMPUTERIZED TECHNIQUE FOR ESTIMATING THE HYDRAULIC CONDUCTIVITY OF AQUIFERS FROM SPECIFIC CAPACITY DATA
Authors: Bradbury Kenneth R. , Rothschild Edward R.
Published: March 2006

Abstract. Specific capacity data obtained from well construction reports can provide useful estimates of hydraulic conductivity (K). A simple computer program has been developed which can correct specific capacity data for partial penetration and well loss and, using an iterative technique, provide rapid estimates of K at hundreds of data points. The program allows easy data handling and is easily linked with existing statistical programs or contour mapping routines. The method was tested at two field sites in Wisconsin, one underlain by a sandy outwash aquifer, the other by fractured dolomite. In both areas, estimates of K from corrected specific capacity data agree reasonably well with data from pumping tests.
Sustained‐Yield Ground‐Water Planning by Goal Programing
Authors: Yazdanian Amin , Peralta Richard C.
Published: March 2006

A method for determining a spatially distributed set of ground‐water withdrawals that maintains a regionally “optimized” potentiometric surface is presented. A goal‐programing approach, in its quadratic form, is used to minimize the sum of squares of differences between the optimized surface and a “target” potentiometric surface. Constraints on withdrawals and recharge, imposed through a two‐dimensional ground‐water flow equation, and bounds on drawdowns assure that the withdrawal strategy developed is realistic and physically feasible. Application is demonstrated using data from the Grand Prairie region of Arkansas.
Hydrogeology of an Atoll Island: A Conceptual Model from Detailed Study of a Micronesian Example
Authors: Ayers Jerry F. , Vacher H. L.
Published: March 2006

Findings from a detailed hydrogeologic study of a Micronesian atoll island are combined with published descriptions of the hydrogeology of other atoll islands. The purpose is to propose a conceptual model which describes how the occurrence and flow of ground water in atoll islands are related to the underlying geologic framework. The study island is Deke, a small, uninhabited island on Pingelap Atoll in the Eastern Caroline Islands.

Integrated studies on Deke of surface geology and physiography, water levels and their variation, surface geophysics (seismic refraction and resistivity), and subsurface core samples indicate a hydrogeologic system that is more complex than would ordinarily be expected for a small and, at first glance, uncomplicated island. Of utmost importance to the occurrence and flow of ground water is the fact that the island straddles the lagoonward edge of the very firmly indurated reef‐flat plate. This plate is a hard, impermeable substrate beneath the northern portion (ocean side) of the island, occurs at sea level, and is underlain by unconsolidated or loosely cemented sediments. Study results indicate that this reef‐flat plate acts as a confining bed along the ocean side of the lens; elsewhere the lens is unconfined, receives recharge directly, and forms a thicker fresh‐water nucleus.

The conceptual model of atoll‐island hydrogeology involves a dual aquifer system: (1) an aquifer of mostly unconsolidated Holocene sediments resting on (2) a once emergent and now very permeable Pleistocene limestone platform. The Holocene aquifer, which is where the island lens occurs, is heterogeneous with respect to its hydraulic properties and is confined in part of the island and unconfined elsewhere, with the location of the two regions depending on where the island sits relative to the pinchout of the reef‐flat plate. In the unconfined region, there is a hydrologically‐important central depression, where low lying sediments are enclosed by ocean‐derived washover fans and a lagoon‐bordering dune. This area is a likely ground‐water sink due to direct evapotranspiration during the dry season. Accordingly, the model includes two flow patterns: a wet‐season pattern radiating outward from the unconfined lagoon‐side of the island, and a dry‐season pattern that includes a superimposed area of centripetal flow at the central depression.
OCCURRENCE OF VOLATILE ORGANIC CHEMICALS IN NEBRASKA GROUND WATER
Authors: Goodenkauf Owen , Atkinson Jon C.
Published: March 2006

Abstract. This report summarizes results of monitoring programs for volatile synthetic organic chemicals (VOCs) in Nebraska's private and public water‐supply wells conducted by two State agencies. Of 97 community water‐supply systems sampled as of June 1984, 16.5 percent (16 systems) showed quantifiable levels of at least one VOC. Detectable amounts of one or more VOCs were measured in samples from 15.9 percent (10) of 63 private wells sampled in 1982. These percentages are consistent with results of other State and national surveys.
Evaluation of Transient Electromagnetic Soundings for Deep Detection of Conductive Fluids
Authors: Stewart Mark , Gay Michael C.
Published: March 2006

Transient electromagnetic sounding methods (TEM) have several advantages over DC resistivity soundings. The principal advantage is that sounding depths several times the receiver‐transmitter spacing can be achieved, resulting in less cumbersome field work and more flexible sounding site selection. The TEM method was tested using a commercially available instrument (Geonics EM‐37) in the Gulf Springs region of west‐central Florida to locate the saltwater interface in the Floridan Aquifer. The Floridan is a thick (200 m), unconfined, karstic, carbonate aquifer within the study area. High annual rainfall and internal drainage create a deep and dynamic interface.

Eighty transient soundings were completed in 18 field days. Seventy‐one soundings used a square 80 m × 80 m transmitter loop, and the other nine used a 160 m × 160 m coil. The interface was easily detected from a minimum depth of 60 m to its maximum depth of about 140 meters. Also, a high‐resistivity, low‐porosity zone was detected at depths ranging from 180–250 meters. The TEM data compare well with available chloride concentration data. The TEM interface corresponds to chloride values in excess of 200–400 mg/1. The sounding curves obtained suggest that with presently available instruments the TEM method is not well‐suited for shallow soundings (less than 40–50 meters).
Relations Between Permeability and Electrical Resistivity in Granular Aquifers
Authors: Huntley David
Published: March 2006

Increased demand for quantitative answers to ground‐water problems, particularly associated with the use of numerical models, has increased the need to accurately determine the distribution of hydraulic parameters. Researchers have attempted to find correlations between electrical resistivity and the permeability of fresh‐water aquifers since 1951. Several recent studies report either direct or inverse relations between apparent formation factor and aquifer permeability. The basis for these relations is a direct or inverse relation between porosity and permeability and, as matrix conduction effects are not taken into account, constant fluid conductivity is either implicitly or explicitly assumed.

Laboratory experiments conducted on granular materials suggest that matrix conduction (surface conduction) effects are either as important as, or dominant over, porosity‐permeability relations. Our experiments on granular materials show only weak relations between true formation factor and permeability. Relations between apparent formation factor and permeability are good only for constant fluid conductivity. Most importantly, the strongest relationship found was that between permeability and matrix conductivity.

These data suggest either that (1) relations between permeability and apparent formation factor must be applied in very restricted geologic environments and only where fluid conductivity remains relatively constant, or (2) more fundamental relations between matrix conductivity and aquifer permeability should be applied.
Ground‐Water Dams for Rural‐Water Supplies in Developing Countries
Authors: Hanson Goran , Nilsson Åke
Published: March 2006

The use of groundp‐water dams to store water in regions with arid or tropical climates is a method that has received considerable attention in the last few years. By storing water behind subsurface dams in natural aquifers or in the sand accumulated in sand storage dams, the disadvantages of conventional surface storage, such as high evaporation rates, pollution, siltation, and health hazards, may be avoided. The techniques are very old, but only recently have there been some attempts to make systematic studies and to develop proper siting, design, and construction methods. This paper presents the experience gained from existing structures all over the world and describes the physical setting in which the techniques may be applied. Design and construction alternatives are shown, and case studies from India and Ethiopia are presented. The construction of ground‐water dams may be a feasible solution to water‐supply problems in many parts of the world if preceded by proper planning and site surveys.
Recovering Fresh Water Stored in Saline Limestone Aquifers
Authors: Merritt Michael L.
Published: March 2006

Numerical modeling techniques are used to examine the hydrogeologic, design, and management factors governing the recovery efficiency of subsurface fresh‐water storage. The modeling approach permitted many combinations of conditions to be studied. A sensitivity analysis was used that consisted of varying certain parameters while keeping constant as many other parameters or processes as possible. The results show that a loss of recovery efficiency resulted from: (1) processes causing mixing of injected fresh water with native saline water (hydrodynamic dispersion); (2) processes or conditions causing the irreversible displacement of the injected fresh water with respect to the well (buoyancy stratification and background hydraulic gradients); or (3) processes or procedures causing injection and withdrawal flow patterns to be dissimilar (dissimilar injection and withdrawal schedules in multiple‐well systems). Other results indicated that recovery efficiency improved considerably during the first several successive cycles, provided that each recovery phase ended when the chloride concentration of withdrawn water exceeded established criteria for potability (usually 250 milligrams per liter). Other findings were that fresh water injected into highly permeable or highly saline aquifers would buoy rapidly with a deleterious effect on recovery efficiency.
Aldicarb Studies in Ground Waters from Florida Citrus Groves and Their Relation to Ground—Water Protection
Authors: Dierberg Forrest E. , Given Chris J.
Published: March 2006

The disappearance of aldicarb [2–methyl–2(methylthio) propionaldehyde 0‐(methylcarbamoyl) oxime] and its two toxic degradation products, aldicarb sulfoxide and aldicarb sulfone, were measured in laboratory studies using ground waters and subsoils collected from citrus groves in Indian River County, Florida, and incubated under controlled conditions which best represented the in situ environment. The half‐life times for the disappearance of aldicarb and its two oxidized sulfur derivatives in ground‐water‐saturated subsoils ranged from 10–26 days. Based on the degradation rates found in this study, hydrologic parameters obtained for Indian River County subsoils, and amounts of total toxic residue reported entering Florida ground waters, it was estimated that toxic residues in aldicarb‐contaminated ground waters in Indian River County would migrate only short distances (0.3–5.2 m) before conversion of toxic residues to nontoxic residues was complete.
ODE TO THE SAN LUIS DRAIN
Authors: Thomas Harold E.
Published: March 2006

Abstract. The San Luis Drain (SLD) has enabled us to learn quickly the facts and effects of irrigating only 8,000 acres of seleniferous soils: the dissolving and organic uptake of selenium, its dissemination from ponds, entry into food chains, and accumulation in a wide variety of biota and detritus. If deprived access to SLD, the Westlands Water District (WWD) could direct their toxic wastes down natural slopes by trickling or sumps and drain ditches, but this means toward the Mendota Pool and the Main Canal and Outside Canal which carry water for irrigation and domestic wells; that is more ominous to Merced County than the SLD ever was.

The WWD needs detailed testing and mapping of its irrigable lands to discriminate the areas of seleniferous soils from those which are safe for irrigation. In the meantime, in irrigated lands above the Delta‐Mendota Canal, all sumps and drains should be monitored for selenium in toxic concentrations, and irrigation should cease in the areas producing the excessive selenium. Monitors along the Outside and Main Canals (below drainage from known seleniferous areas) might be needed for preservation of good quality, perhaps by dilution with CVP water.