ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00452.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe Bouwer and Rice slug test was developed to measure aquifer hydraulic conductivity around boreholes (production, monitoring, or test wells). The wells can be partially penetrating and partially screened, perforated, or otherwise open. The slug test can be based on quickly with‐ drawing a volume of water from the well and measuring the subsequent rate of rise of the water level in the well, or by adding a slug of water and measuring the subsequent rate of fall of the water level in the well. While originally developed for unconfined aquifers, the method can also be used for confined or stratified aquifers if the top of the screen or perforated section is some distance below the upper confining layer. Anomalies (“double straight line effect”) sometimes observed in the measured rate of rise of the water level in the well are attributed to drainage of a gravel pack or developed zone around the well following lowering of the water level. The effect of this drainage can be eliminated by ignoring the early data points and using the second straight line portion in the data plot for calculation of hydraulic conductivity. The method is applicable to any diameter and depth of the borehole, provided that the dimensions of the system are covered by the ranges for which the geometry factor Rehas been worked out. The smaller the diameter of the hole, however, the more vulnerable the results will be to aquifer heterogeneities and to inaccuracies in estimating effective well diameters. Computer programs for rapid processing of the field data have been deve

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00453.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTIn many island and coastal ground‐water problems, the position of the ground‐water/free sea‐water interface is an essential, but highly dynamic boundary. The fluctuating boundary commonly is simplified to a fixed position in problem formulation. This fixed position is frequently taken as the location of local mean free‐water level (mean sea level) in the adjacent salt‐water body. However, tidal fluctuation and wave runup on a sloping beach cause mounding of sea water in the upper beach with a consequent effective mean sea level as much as two feet higher than local mean sea level. This phenomenon is particularly important in small islands and coastal situations where the ground‐water flow pattern is highly dependent on the position of the effective boundary both vertically and horizontally. In coastal hydrological situations, a good approximation for the effective vertical position, i.e. effective mean sea level, of the ground‐water/free sea‐water boundary is the mean equivalent salt‐water head in a deep discretely screened piezometer located in the beach near the upper swash line. The veracity of this technique is demonstrated by the results of field research in a New Engl

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00454.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe hydrologic response to development of three of the most heavily pumped sedimentary aquifer systems in the United States is similar in some aspects and different in others. In the semiarid West, an unconfined sand aquifer and a confined sand and clay aquifer system have been subjected to withdrawals that are far greater than predevelopment recharge rates. As a result, the aquifers have large losses of ground water from storage. In the humid East, pumpage from a carbonate aquifer system has resulted in induced recharge and diversion of natural discharge with insignificant loss from storage. However, the following responses to development are common in all three aquifer systems: (1) ground‐water circulation has increased,(2) rates of recharge have increased—mostly due to recirculation of pumped ground water, or infiltration of imported surface water used for irrigation in the semiarid West,(3) locations of recharge areas have changed, and (4) natural discharge has decreased.Regional water‐level declines associated with ground‐ water development are inevitably accompanied by some combination of elastic compaction of aquifer material, inelastic compaction of fine‐grained sediments and land subsidence, dewatering of aquifer material near pumping centers, and induced formation of sinkholes. The degree to which these changes occur is dependent on: (1) rates of pumping in relation to available recharge, and (2) lithology, specifically the proportion of sand, gravel, silt, clay, and carbonate rock that comprise the aquif

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00455.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA recent tectonic model and subsequent gravity survey and basement modeling have raised questions concerning the size of the Camas Prairie ground‐water storage basin and the hydrodynamic properties of the Camas Creek drainage basin. This paper addresses storage basin dimensions using an anomalous mass determination from a plot of residual gravity, and presents estimates of recharge and underflow from a mass‐balance study. Underflow may transport much of the water [2·73 (105) acre‐feet/yr] (ac‐ft/yr) calculated as residual in the mass‐balance study, and transport is from the Camas Prairie storage basin south to the Snake Plain Aquifer via permeable strata in the Mount Bennett Hills surface drainage divide. Results of the anomalous mass study suggest that the volume of ground water stored in the Camas Prairie basin is 39 (106) ac‐ft, considerably greater than previously estimated. Similarly, recharge to the Camas Prairie basin is estimated at over 7(105) ac‐ft/yr, one order of magnitude greater than ear

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00456.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTWater‐table altitude, a controlling factor for ground‐ water flow, was estimated from detailed topographic data by subtracting the estimated depth‐to‐water. Land‐surface altitude of the Coastal Plain in the south‐central United States varies from 0 to more than 800 feet above sea level. Predevelopment depth‐to‐water in 6,825 wells less than 150 feet deep averages 25.7 feet (standard deviation, 19.5 feet). Most water‐table‐altitude variation is due to variation in land‐surface altitude and not due to variation in depth‐to‐ water. Digital topographic data, from 1:250,000 scale maps for every 30 seconds of latitude and longitude are available for the continental United States. About 90 altitudes were averaged for each 25‐square‐mile block of a rectangular grid used for ground‐water flow modeling. Multiple linear regressions of predevelopment water‐level data and topographic data were used to derive empirical equations relating water‐table altitude to topography.The regression method was more consistent, efficient, and accurate than manually digitizing values from manually contoured water‐table maps. Water‐table maps usually are prepared from few data that are concentrated in topographically flat areas. Manually digitizing water‐table maps on a regional scale introduces additional error. About 35 percent of the water‐table altitudes obtained manually were greater than average land‐surface altitudes from topographic data. The mean difference between water‐table altitudes from the two methods was less than 10 feet, which indicates no systematic

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00457.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTAs depth below the water table increases, there can be significant spatial variations in fluid density. Fluid density is a function of fluid temperature, total dissolved solids and gases content, fluid compressibility, and the force of gravity. Variations in fluid density can affect the applicability of measured water levels to represent fluid pressure at depth and the existence of a scalar fluid potential. Where ground water is sufficiently heterogeneous, fluid pressure and fluid density must be known spatially to properly determine the three‐dimensional impelling force per unit mass E =— [gk + (1/p) ▽P]. Assuming that the water‐level elevation in deep boreholes represents a fluid potential may result in significant errors in determining flow directions and quantities under conditions of a variable density fluid and low hydraulic gradients. Boreholes constructed to investigate the feasibility of deep geologic disposal of nuclear waste have penetrated to depths greater than 1,500 m below the Earth's surface. In these deep boreholes, fluid density variations may need to be considered as a part of the hydrologic analysis. Fluid density variations with depth, predicted as general cases based on simple models, indicate the relative importance of temperature, compressibility, and gravity variations at three potential high‐level nuclear waste repository locations. Fluid density generally decreases with depth for sites where geothermal gradients are greater than 20°C/km, and thermal expansion can offset the effects of fluid compr

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00458.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTExisting institutions for protecting surface‐ and ground‐water quality provide uneven results across the nation. Pollutants are transferred across media and political boundaries, important contaminants are not addressed, important sources of pollution are not controlled, and accountability in achieving measurable objectives is not assured. Examples from the seven‐state region served by the Tennessee Valley Authority (TVA) document the wide range of ground‐water contamination issues facing the nation and the importance of interconnections between subsurface and surface waters–both hydrologically and institutionally. National legislation seems imminent to overcome institutional barriers that promote fragmented, ineffective, and expensive approaches.Unified management of subsurface‐ and surface‐water quality makes both hydrologic and institutional sense for dealing with cross‐media, cross‐agency linkages causing water pollution. Congressional testimony presented by TVA suggests that this unified water quality management can be achieved through a narrow amendment to the Clean Water Act requiring state adoption of (1) surface‐ and subsurface‐water classification systems, (2) surface and subsurface numerical standards, and (3) conjunctive surface‐ subsurface‐water quality management programs. National minimum program requirements, federal funding, and federal program/facility compliance would provide leadership in creating new local/state/federal partnerships targeted to priority geographic areas. In this way, the state comprehensive program would become the hub around which the spokes of all different environmental and natural resource management (technology‐based control) programs with surface‐ or ground‐water quality implications would be integrated. This proactive water quality management approach would be less costly to the public than existing reactive approaches which have left taxpayers with a half trillion dollar remedial action bill for cleaning up our surf

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00459.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA reference repository is examined for environmental compliance utilizing minimum performance standards as established by the Nuclear Regulatory Commission and the Environmental Protection Agency. These standards stipulate the amount of time the radionuclides must be retained in the barrier, the acceptable release rates from the barrier, and the acceptable mass release that can be registered at the accessible environment over a 10,000‐year time frame. The only natural, or geologic barrier standard specified is a minimum ground‐water travel time of 1000 years from the engineered barrier to the accessible environment. Other natural barrier processes including geochemical retardation and mass transfer, dilution, and dispersion are not specified. In attempting to determine the role that these unspecified components must play in order to comply with the mass release standard, we find that their role is minimal to the extent that virtually any rock type that can satisfy the minimum ground‐water travel time of 1000 years will satisfy the mass release requirements at the accessible environment. Full compliance with a concentration standard at the accessible environment requires that the nuclides contained within the larger inventories be fully contained with the controlled zone between the engineered barrier and the accessible envir

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00460.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTDischarge of naturally occurring brine from the Southern Great Plains regional ground‐water flow system significantly affects water quality in local aquifers in the Concho River watershed in West Texas. Aquifers in outcropping Permian rocks locally contain brine and hydrocarbons at depths as shallow as 135 ft (41 m). Maps of hydraulic head, salinity, and hydrochemical facies and graphs of ionic ratios and stable isotopic composition locate where brackish to saline ground water occurs naturally as a result of mixing between locally recharged meteoric water and subsurface brine in the regional flow system. Br/Cl, CI/SO4, Ca/Na, and δD/δ18O ratios distinguish between brine sources in the mixing zone. For example, chemical composition of brackish‐to‐saline shallow ground waters beneath the Concho River watershed more closely resembles the composition of Permian than of Pennsylvanian formation brines. Other possible salinity sources include (1) seepage of salt water from rocks beneath oil‐field brine‐disposal p ts, which ceased operation in the late 1960 s, and (2) upward flow of artesian salt water across confining beds through decades‐old abandoned oil‐exploration holes. These sources are superposed on the naturally occurring mixing zone between brine

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1989.tb00461.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY