ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02142.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTFault creep has stopped or slowed in the eastern part of the Houston, Texas, land subsidence area where reductions in pumping of ground water have allowed water levels to recover partially. Creep has continued across faults in the western part where heavy pumping causes water levels to continue to decline. The observations support the long‐suspected relation between historical faulting and withdrawal of ground water and indicate that partial water‐level recoveries can reduce fault movement and structural dam

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02143.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThe Permo‐Triassic sandstone aquifer of northwest England has been a major source of ground‐water supply since the early 19th century. Between Liverpool and Manchester, ground‐water resource development has led to a considerable lowering of the water level inland and intrusion of sea water from the Mersey Estuary and Manchester Ship Canal. As part of a detailed investigation of resource management, a two‐dimensional finite‐difference flow model was developed to represent aquifer behavior for the period 1840 to 1980. Subsequently, this model was used to predict the effects of implementing various management strategies over a 40‐year period ending 2020.Results indicate that ground‐water withdrawals have exceeded natural replenishment by an average of 100% during the past 50 years. In this time the potentiometric heads have responded remarkably slowly to the flow imbalance, a resilience that is largely attributed to the inflow of sea water at rates only marginally less than recharge from meteoric sources. Careful development of the fresh ground‐water resources has minimized water quality problems along the estuary and ship canal, and the model clearly shows how controlled inflow of saline water can considerably enhance the recovery of fresh ground‐water reserves. Difficulties arise only when excessive exploitation accelerates water quality deterioration. Model calculations indicate that inflow of saline water would continue for over 10 years following complete cessation of fresh ground

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02144.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTTen wells were installed to monitor the water‐table elevation and volatile organic compounds (VOCs) in ground water underlying Hastings, Nebraska. Trichloroethylene (TCE) was the most frequently detected VOC and had the highest concentration (1750 μg/1) in these monitoring wells. Perchloroethylene (PCE), 1,1‐dichloroethylcne (1,1‐DCE), 1,2‐dichloroethane (1,2‐DCA), and 1,1,1‐trichloroethane (TCA) also occurred in one or more of the monitoring wells. The vertical and areal VOC distribution in both the contaminated monitoring wells and the city's contaminated municipal wells are largely related to withdrawal caused by heavily pumped, nearby municipal and industrial wells. A computer model was used to demonstrate the impact historic site changes in high capacity well withdrawal have on the local water‐table configuration. Two sites of suspected VOC sources are designated for furthe

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02145.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTMany state and federal agencies routinely collect ground‐water quality data to meet a variety of objectives. The WATSTORE (Water Data Storage and Retrieval System) data files of the U.S. Geological Survey containing raw ground‐water quality data from 4,388 wells and the MSIS (Model State Information System) data files of the U.S. EPA containing finished (blended and/or treated) ground‐water quality data from 2,137 public water‐supply sources are the only two large computer‐coded data files on Iowa ground‐water quality. These two data bases, by themselves, provide significant insights regarding the distribution of chemicals in different hydrogeological environments and the compliance status of PWS sources with reference to drinking‐water quality standards in Iowa. With minor modifications, these two data bases can be integrated to: (a) provide statistical, spatial, temporal, and geological summaries of observed ground‐water quality; (b) determine the extent of exposed populations to various contaminants in their different concentrations; (c) provide necessary information to reduce the existing list of contaminants and include some of those that are not being monitored now; (d) identify gaps in current data‐gathering efforts and prioritize the various components of future monitoring programs; (e) identify potential linkages for the combined use of ground‐water quantity and quality, socioeconomic, land‐use, and public health data; and (f) alert policy makers to potential ground‐water quality problems facing the state. Some of the limitations of the two data bases and the need for integrating them is demonstrated by a comparative

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02146.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTThree case histories are presented to illustrate the problems encountered using some monitoring well installation, purging, and sampling techniques. Hollow‐stem auger‐ing was found to pose problems during the installation of monitoring wells in terms of potential for cross‐contamination of strata, the inability to emplace an adequate filter pack, the potential for smearing natural clays into sand and gravel strata, and the possible need for excessive purging of sediments that accumulate between sampling events. Cable tool drilling was found to allow construction of high quality wells, but was slow and expensive. Concern over the potential for increased emissions of noxious vapors from the borehole when drilling with the air rotary method prevented its use in situations where highly contaminated strata were likely to be encountered. A hybrid drilling technique, augering with temporary casing, was able to provide the advantages, and minimize the disadvantages, of the foregoing drilling methods.The installation of vertically separated clusters of monitoring wells lent important insights into the potential movement of a contaminant plume. Detailed aquifer tests provided needed information on the hydraulic behavior of the subsurface strata occupied by the plume so that potential pathways of contaminant transport could be more accurately identified. Obtaining reliable data from such tests depended greatly on the ability of each monitoring well to act as a high quality hydraulic observation well. The selection of drilling and installation techniques that ensured minimal disturbance of the near‐borehole environment provided the best guarantee of such perf

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02147.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTAnalysis of the direction of ground‐water flow across the host rock at the proposed high‐level nuclear‐waste repository site in Deaf Smith County, Texas, is complicated by vertical and lateral changes in the density of formation fluids in the various hydrogeologic units that overlie and underlie the proposed host rock. Because the concept of hydraulic head is not valid when evaluating vertical hydraulic gradients in a variable‐density flow system, other methods were used to determine the direction and magnitude of vertical hydraulic gradients at the proposed site where the specific gravity of formation fluids varies between 1.00 and 1.28. The direction of ground‐water flow across the proposed host rock, an 80‐foot‐thick salt bed in the Lower San Andres Formation, was determined by calculating vertical hydraulic gradients based on formation pressure and fluid density data, and by analysis of pressure‐depth diagrams. Based on data from the vicinity of the proposed site, both methods indicate the potential for downflow across the host rock. Downflow or predominantly horizontal flow is considered a favorable prewaste emplacement condition because it prolongs the‐travel time to the biosphere of any naturally or accidentally relea

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02148.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTA sampling device is described which collects ground‐water samples containing volatile organic compounds and dissolved gases. The device protects the samples from volatilization losses from the time of collection until the time of analysis. It can be produced in a wide range of sizes and allows access to wells with inside diameters as small as one centimeter. The sampler is designed to be lowered in a well to the desired depth, depressurized to slightly below thein situpressure to allow entry of the sample, and then repressurized prior to being returned to the surface. During collection and storage, the sample is exposed only to copper and stainless steel. An optional quartz prefilter can also be used. Crimping sections at either end of the sample reservoir seal the pressurized sample during its return to the laboratory. The sampler is designed to be interfaced to analytical instruments for the direct, quantitative transfer of all analyte

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02149.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTFactors for a normal distribution are given such that one may be 99% confident that the two‐sided prediction interval x̄+rsor the one‐sided prediction interval x̄+rswill contain all of thekfuture values, where x̄ andsare the sample mean and standard deviation obtained fromnprevious values. In the context of ground‐water monitoring, the future samples may represent new monitoring values at each ofkdowngradient wells, and thenprevious values might be the historical monitoring results for one or more upgradient wells. The Tables provided in this paper allow the computation of one‐sided and two‐sided99%prediction intervals for previous sample sizes ofn= 4 to 100 and future samples ofk= 1 to 100. Modification of these intervals for log‐normally distributed data is

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02150.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

ABSTRACTA simplified mathematical model is developed to predict the equilibrium location of upconed interface due to a horizontal well in an unconfined coastal aquifer of finite thickness. The model is based on Dupuit assumption and Ghyben‐Herzberg approximation with modified boundary conditions along the shoreline deduced from available analytical solutions. For a specified natural flow condition, the amount of fresh‐water discharge to the sea as well as interface profile and length of intrusion can be determined. With the specification of the permissible extent of upconing from the natural interface location at any section, the model provides an estimate of the amount of water that can be withdrawn by a horizontal well, the upconed interface profile, and the additional length of intrusion. The computed interface profile for the natural flow condition is found to be in good agreement with the results of available analytical solutions. Comparison with the laboratory tests for the upconing case indicates that the simplified model provides a reasonable approximation of the interface profile for assessment of water withdrawal from a coastal aquifer at the initial stage of plann

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1987.tb02151.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY