ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00474.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA geoelectric survey, composed of vertical electrical soundings, was conducted over part of the lower Platte Valley alluvial aquifer of east‐central Nebraska. Survey results, in conjunction with seismic‐survey data and test‐ hole‐log information, provided the basis to map the areal extent and thickness of a near‐surface, low‐permeability clay unit. Because of the low hydraulic conductivity of the clay, the unit forms a confining layer over a significant part of the aquifer.Generally, the approach to evaluating the lower Platte Valley alluvial aquifer for sustained yield has been to assume that the entire flow system is under water‐table conditions. However, numerical‐model simulations with and without the clay unit indicate that this confining layer has a significant effect on the hydraulic behavior of the groundwater flow system under pumping stresses.An estimate of the bulk porosity of the aquifer was made by using geoelectric data and applying the Archie equation. Values of porosity ranged from 0·27 to 0·43; although reasonable for fluvial sand and gravel, the range is higher than p

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00475.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTPrevious theoretical and empirical investigations of the relation between particle size and intergranular permeability have resulted in the well‐known formula for intrinsic permeability (k)where d is particle diameter, and c is a dimensionless constant. Statistical power regression analyses were per‐ formed on 19 sets of published data on size and laboratory permeability of unconsolidated sediments. The exponent of grain diameter ranged from 1.11 to 2.05, but most values were significantly less than 2.0. Results indicate that the permeability/grain size relation alternatively may be expressed, from an empirical basis, asValues of c and the exponent both generally decrease with decreased textural maturity and increased indurat

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00476.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTAreal and temporal variations in physical and chemical characteristics of ground water in the Inner Bluegrass Karst Region of central Kentucky were used to evaluate physical controls on hydrochemical variability. The karst region consists of flat‐lying interbedded limestones and shales. Physical attributes of the aquifer were assessed on the basis of spring discharges, static water levels in wells, and pumping tests. Areal and temporal variations in ground‐ water chemistry were determined from major‐ion analysis of water samples from 15 springs and 24 wells over a 17‐ month period.Water samples were divided into three chemical types on the basis of the relative concentrations of the dominant ions; Ca‐Mg‐HCO3, Na‐HCO3, and Na‐Cl water. Ca‐Mg‐HCO3water was divided further on the basis of Ca/Mg molar ratios into Ca subtype water (Ca/Mg>6) and Ca‐Mg subtype water (Ca/Mg<6). All springs are characterized by Ca subtype water. Pumping tests show that hydraulic conductivities in zones of Ca‐Mg‐HCO3water are significantly higher than those in zones of Na‐HCO3and Na‐Cl water. There is no regional trend in the distribution of these water types.Temporal fluctuations in water chemistry correlate with seasonal fluctuations in recharge. Large seasonal variations in ionic concentrations occur primarily in Ca subtype water. Hydraulic conductivities, seasonal variations in ionic concentrations, and TDS suggest that ground‐water residence time is the primary control on the occurrence of the different water types. Differences in residence time are attributed to the presence of discontinuous, horizontal shales that control the rate and depth o

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00477.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTSeveral sets of values are available for the shape factor of the cylindrical injection zone used to perform a field permeability test. Depending on the selected value, the resulting difference for hydraulic conductivity may reach 40% for long intake zones, and more than 100% for short intake zones. The commonly used shape factor is that given by Hvorslev (1951). Seven other factors derived from numerical models are now available: they differ from Hvorslev's factor by up to 100%. Three possible reasons for the differences are examined. Reference is made to Laplace's equation and related mathematical results derived before 1945. Shape factor values obtained by numerical methods are shown to be more or less accurate solutions of particular cases when impervious or recharging boundaries exist close to the injection zone. Their influence upon the shape factor value can be calculated analytically, as shown in a detailed example. Analytical shape factor equations are given for a cylindrical injection zone with either a pervious or an impervious bottom. Based on the method of image wells, two other equations are established to correct the shape factors if draining (constant head) or impervious layers are known to be located close to the injection zone. These equations should be used for field permeability tests in boreholes or piezometers.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00478.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA method using the nonlinear least‐squares and finite‐ difference Newton's method is presented to identify the parameters from pumping tests in homogeneous and isotropic leaky aquifers both for the situations with and without storage effects in the aquitard. Based on the least‐ squares approach, the sum of the squares of differences between the observed drawdowns and predicted drawdowns using the estimated parameters is minimized. The finite‐ difference Newton's method is used to solve the system of nonlinear least‐squares equations for the unknown aquifer parameters.Comparisons of the results among the proposed method, graphical method, and sensitivity analysis method when analyzing various data are presented. The proposed method has the merit of good accuracy and quick convergence from some initia

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00479.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

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

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00480.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA mathematical model for transport and transformation of a pesticide and its metabolites in the soil is presented. Mechanisms for convective‐transport, hydrodynamic dispersion, ionic exchange, biological degradation, and hydrolysis are accounted for in the mathematical formulation. The major assumptions used in developing the model include: flow in the soil is in the vertical direction and one‐ dimensional, soil system is homogeneous and isotropic, volumetric water content and Darcy's flux are constant in time and space, and a linear reversible Freundlich isotherm describes the concentrations in the aqueous and adsorbed phases. Based on the outlined assumptions and Laplace transform techniques, analytical solutions for the concentrations of the parent material and its metabolites are presented. The applicability and potential of the model are demonstrated by predicting the transport and transformation of aldicarb (a nematicide of agricultural significance) and its metabolite, aldicarb sulfoxide, in the s

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00481.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTFresh water is found at depths up to 1000 feet in basal Pennsylvanian sandstone aquifers along the southern margin of the Illinois Basin. These aquifers, though not highly productive, represent a significant potential source of ground water in a region of very limited ground‐water supplies. A pilot study was undertaken in southwestern Illinois using geophysical logs and limited hydrologic data to evaluate the potential of these aquifers. Water quality, porosity, and permeability were estimated from the geophysical logs; these data were then used in conjunction with data from aquifer performance tests to delineate zones of potable water. The data indicate that fresh‐water lenses extend basinward in sandstone paleochann

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00482.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe ground‐water geochemistry of glacial drift and bedrock of selected areas of New England, New York, and Pennsylvania differs considerably among the areas as a result of differences in bedrock geology. The New England study area is underlain primarily by feldspathic rock, large areas of New York are underlain primarily by carbonate and terrigenous sedimentary rock and some evaporite deposits, and glaciated areas of Pennsylvania are underlain primarily by clastic sedimentary rock with minor carbonate rocks. Mean concentrations of most solutes are greatest in the New York area and least in the New England area.In New England, the ground‐water geochemistry results mainly from the reaction of CO2‐charged water with feldspar and other primary silicates. Water in the New England bedrock is more highly evolved geochemically than water in the drift, presumably as a result of its longer residence time.In the New York area, the geochemistry of water in both types of aquifers results mainly from carbonate‐ mineral dissolution. Water in most glacial drift and bedrock is saturated with respect to calcite. In some parts of New York, the dissolution of evaporite minerals has a marked effect on the water chemistry of the bedrock.In most of the Pennsylvania area, the geochemistry of water in both types of aquifers indicates that, although carbonate minerals are the principal reactants, their influence on water chemistry is less than in New York. In parts of Pennsylvania, chemical differences between ground water from drift and ground water from bedrock are attributed to a higher proportion of reactive minerals in the drift than in the local bedrock as a result of glacial tr

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00483.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY