ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01021.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTFractured geologic media are typically considered to behave as equivalent porous‐media continua for the purposes of hydrologic testing and modeling. The equivalent‐continuum effective porosity of a fractured medium is frequently measured using tracer tests performed over distances that are small relative to the scale of interest in hydrologic and transport modeling. The larger‐scale value of effective porosity can differ from the smaller‐scale measured value by several orders of magnitude, depending in part on the relative degree of fracture continuity between inflow and outflow zones at the different scales. Based on the results of a simplified numerical modeling study for fractured media with poor continuity at the location and scale of interest, flow is dominated by the intact rock matrix, resulting in a higher effective porosity. For fractured media with uninterrupted fracture continuity at the location and scale of interest, the effective porosity may be substantially lower due to the fracture‐dominated nature of

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01022.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTA two‐dimensional finite‐element model has been adapted to simulate the aquifer underlying the Nile Valley of Egypt. Calibration of the model led to the determination of the interaction between the ground water and the Nile surface water. Results obtained from the model were compared with those obtained from simple hydrologic budget analyses and were found to be quite comparable. The model is, thus, considered to adequately represent the ground‐water system of the Nile Valley and may be used to forecast the effects of managing the integrated ground‐water/surface‐wat

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01023.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThis is a short description of undergraduate and graduate hydrogeological training in Soviet universities. Some advantages and disadvantages of this training are pointed out. The necessity of the exchange of ideas and scientific literature between American and Soviet educators in the field of hydrogeology is stressed.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01024.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTIncreased 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 ap

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01025.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe carbonate chemistry was measured at various springs and surface stations along three river basins in the northwestern karst belt of Puerto Rico. Most surface waters are supersaturated with respect to calcite, and carbon dioxide pressures are close to atmospheric value. Spring waters have higher CO2 pressures but also tend to be supersaturated. Water hardnesses are not dramatically greater than those observed in temperate climate karst.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01026.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTGround‐water recharge to a shallow, unconfined, fractured dolomite aquifer underlying agricultural land in Lancaster County, Pennsylvania occurs by two mechanisms. Direct recharge occurs through pathways such as near‐surface bedrock fractures and sinkholes, and affects dissolved nitrate concentration of ground water within two to three days; its effects last only about one week. Gradual recharge occurs through small channels and pores in the unsaturated zone and affects dissolved nitrate concentration for several weeks or more after the effects of direct recharge have dissipated. Whether recharge causes an increase or decrease in dissolved nitrate concentration depends on the amount of nitrogen‐rich manure spread on the site prior to the storm. Direct recharge from a storm in March 1984, a month in which 18 tons of manure were spread, resulted in a rapid decrease in dissolved nitrate concentration of about 2.5 milligrams per liter (mg/1) as nitrogen. Direct recharge from a storm in May 1984, after 384 tons of manure had been spread in April, resulted in a rapid increase in dissolved nitrate concentration of about 3 mg/1 as nitrogen. Concentration changes caused by gradual recharge several weeks or more after the storms were of the same magnitude as those caused by direct recharge during the

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01027.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe U.S. Geological Survey is modeling hydraulic flow and thermal‐energy transport at a two‐well injection/ withdrawal system in St. Paul, Minnesota. The design of the finite‐difference model grid for the doublet‐well system is complicated because the aquifer is anisotropic and the principal axes of transmissivity are not aligned with the axis between the two wells.An analytical solution for flow in a doublet‐well system in an infinite anisotropic aquifer was employed in the design of a grid with artificial boundaries placed in the midst of the flow field. Flow‐net analysis was used to determine water flux across an cquipotential boundary and to assign approximate flux values at model boundaries. This enabled the simulation of the effects of the entire flow field, although only a small part was modeled.The validity of the flux values at the model boundaries for the isothermal case was tested by simulation of an eight‐day injection test of ambient‐temperature water. Model‐computed pressures compared very favorably with field‐observed pressures. The validity of boundary‐flux values also was tested for nonisothermal conditions by simulation of injection of 300o F water at 300 gallons per

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01028.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe 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 su

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01029.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTA review of mining‐engineering concepts and studies in mine hydrology suggests a conceptual model linking the strata deformation, hydraulic property changes, and ground‐water impacts due to underground coal mining. The pressure‐arch deformation pattern about a small opening creates a local zone of increased permeabilities and dewatering in the seam and immediate roof, but should not hydraulically affect shallower aquifers. Networks of supported headings, rooms, and pillars intensely drain lower aquifers but only slightly affect higher strata except in areas of naturally high permeability. Longwall mining causes extensive, high‐reaching, well‐defined zones of stress, fracturing, and hydraulic impact, the maximum permeability increases being in the tensile zones immediately above the panel and at the sides of the subsidence trough. In shallow aquifers, permeabilities and ground‐water velocities increase, and hydraulic gradients decline independently of mine drainage.A study of a deep coal mine in the Appalachian Plateau, Pennsylvania indicated: probable hydraulic connections between the mine and shallow aquifers in a principal valley area; no obvious response of water levels in shallow aquifers to undermining by supported headings; and rapid, considerable declines in such water levels in response to nearby longwall mining. These results are consistent with the conce

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1986.tb01030.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY