ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02958.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

ABSTRACTThis classification of aquifers is based upon the properties of rocks which affect ground water. In any region the rocks may be consolidated or unconsolidated. They may be uniform in lithology, or they may consist of alternating layers of different lithologies. They may have been tilted, fractured, or altered in various ways since their formation.Consequently the occurrence of ground water depends not only on the fundamental nature of the rocks but also on their geologic history. The ground water may be found under confined (artesian) or unconfined (water table) conditions. The permeability of an aquifer may be uniform, or it may vary in some regular way, or it may be very irregular because most of the water is in secondary openings.As most geologic situations do not fit well into precise categories, some aquifers may fall into more than one subdivision of this classification.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02959.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

ABSTRACTThe movement of bacteria‐laden waters percolating through fractured crystalline bedrock in mountainous terrain was examined to determine whether effluent originating from domestic waste disposal systems could contaminate shallow ground‐water supplies. Inoculated waters were injected into holes and/or wells at two geologically different test sites (granitic, metamorphic) to evaluate the extent of microbial filtration in or along bedrock fractures. Microbiological examination of tracer waters, sampled both above and below the zone of saturation, was made.Field studies showed that the direction and rate of movement of contaminated ground waters were controlled largely by the anisotropic nature of the geologic stratum, particularly by the orientation of major bedrock fracture sets. Inoculated waters were found to be readily transported by the ground‐water gradient into a downslope well. At one test site, a tracer bacterium traversed a horizontal distance of 94 feet in 24‐30 hours. Continued bacteriological analysis of the contaminated well found the organism to be present for at least five days after inoculation of the upslope well.In the zone of aeration, bacteria‐laden effluent was found to percolate in or along fractures with inadequate filtration prior to entering the ground water. Studies conducted in metamorphic rock demonstrated that while fecal‐type bacteria decreased slightly during percolation through bedrock fractures, total bacterial densities were generally unchanged.From the hydrogeological and microbiological data obtained at both test sites, it can be concluded that moderate percolation rates and minimum distances between water wells and leachfield type waste disposal units are inadequate to protect potable ground‐water supplies from contamination in mounta

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02960.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

ABSTRACTMany municipal, industrial, domestic and farm water supplies throughout the country are derived from wells tapping shallow aquifers that have a high contamination potential from surface derived sources. Unfortunately, water samples from most of these wells are not analyzed on a regular basis even for bacteria or simple chemical pollutants such as nitrate. Practically none of them are routinely checked for more serious contaminants such as viruses, weed killers, pesticides, trace metals, and an almost countless number of toxic chemical compounds commonly used in our environment and eventually discarded in garbage dumps, waste‐burial grounds, or disposal wells. Because of this, the possibility of serious ground‐water contamination often is not discovered until a high degree of contamination is present.Microorganisms contained in water may be effectively removed by filtration in a short distance of travel through fine‐grained earth materials. However, most toxic chemical compounds are not. Instead, these are carried by precipitation recharge to surficial ground‐water reservoirs. After entry such contaminants move downgradient through the aquifer materials, usually at rates of only a few feet per year with little if any dilution, to natural discharge points such as streams, lakes and swamps, or to pumping wells.Ground‐water contamination occurrences from nitrate, arsenic, chromate, cadmium, chlorinated hydrocarbons, and a large number of other toxic chemicals are increasing. These show that a serious threat to public health may be imminent unless all surficial and underground disposal sites of toxic chemicals are located, the extent and magnitude of ground‐water contamination from each site evaluated, and corrective measures applied wher

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02961.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

ABSTRACTSalt water intrusion is an acute problem in the coastal areas of Prince Edward Island. In the town of Summerside, ground‐water supplies are developed from an aquifer hydraulically connected with the sea. Over the past ten years, there has been progressive contamination of the aquifer, particularly in wells close to the seashore.Investigations including test drilling, aquifer testing and chemical studies were undertaken in Summerside to study the nature and extent of the salt water intrusion.Landward encroachment of the saline water is aided by the relatively high transmissivity of the fractured Permo‐Carboniferous sandstone which comprises a semiconfined aquifer. Two separate zones of salt water contamination exist—namely an upper zone from a depth of 0 to 80 feet caused by a landward hydraulic gradient of the fresh water due to heavy pumping and a second zone at a depth of 350 to 400 feet due to intermittent pumping resulting in a raising and thickening of the zone of diffusion. The extent of salt water intrusion is depicted, using hypothetical sec

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02962.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

ABSTRACTA digital model has been developed to simulate the ground‐water flow through a confined aquifer discretized by a nonuniform mesh, using the noniterative alternating direction implicit method. The model results were checked closely with the analytical Theis solution for a homogeneous, isotropic aquifer. The use of the model will result in the following advantages: (1) a reduction in computer core storage and execution time requirements, (2) a closer and better replica of the aquifer boundaries, and (3) a freedom to focus on concentrated areas of interests in the aquifer system.The model was applied as a test case to the isolated sand and gravel aquifer at Elmsvale, Nova Scotia, Canada. With the superposing Musquodoboit River providing a source of recharge to the system, the Elmsvale aquifer would reach an equilibrium after 51 days of continuous pumping at a rate of 0.670 cubic feet per second. Available information suggests that the ground‐water resources potential in the Musquodoboit River Valley is more than sufficient to meet the demand of the valley in the foreseeable fut

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02963.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1973.tb02965.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY