Modeling Techniques for Groundwater Evaluation

Prickett, Thomas A.

doi:10.1016/b978-0-12-021810-3.50006-0

Cited by 68 publications

(54 citation statements)

References 144 publications

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“…Walton and Prickett (1963), Prickett (1968). The names that come to mind are Tyson and Weber (1964) in Los Angeles, Zaoui (1961) at SogrØah and the Chott-el-Chergui in Algeria, Prickett (1975) for a review, and others.…”

Section: Heterogeneity and Numerical Modelingmentioning

confidence: 99%

Dealing with spatial heterogeneity

et al. 2005

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Heterogeneity can be dealt with by defining homogeneous equivalent properties, known as averaging, or by trying to describe the spatial variability of the rock properties from geologic observations and local measurements. The techniques available for these descriptions are mostly continuous Geostatistical models, or discontinuous facies models such as the Boolean, Indicator or Gaussian-Threshold models and the Markov chain model. These facies models are better suited to treating issues of rock strata connectivity, e.g. buried high permeability channels or low permeability barriers, which greatly affect flow and, above all, transport in aquifers. Genetic models provide new ways to incorporate more geology into the facies description, an approach that has been well developed in the oil industry, but not enough in hydrogeology. The conclusion is that future work should be focused on improving the facies models, comparing them, and designing new in situ testing procedures (including geophysics) that would help identify the facies geometry and properties. A world-wide catalog of aquifer facies geometry and properties, which could combine site genesis and description with methods used to assess the system, would be of great value for practical applications.RØsumØ On peut aborder le problme de l'hØtØrogØnØitØ en s'efforçant de dØfinir une permØabilitØ Øquivalente homogne, par prise de moyenne, ou au contraire en dØ-crivant la variation dans l'espace des propriØtØs des roches à partir des observations gØologiques et des mesures locales. Les techniques disponibles pour une telle description sont soit continues, comme l'approche GØosta-tistique, soit discontinues, comme les modles de facis, BoolØens, ou bien par Indicatrices ou Gaussiennes SeuillØes, ou enfin Markoviens. Ces modles de facis sont mieux capables de prendre en compte la connectivitØ des strates gØologiques, telles que les chenaux enfouis à forte permØabilitØ, ou au contraire les facis fins de barrires de permØabilitØ, qui ont une influence importante sur les Øcoulement, et, plus encore, sur le transport. Les modles gØnØtiques rØcemment apparus ont la capacitØ de mieux incorporer dans les modles de facis les observations gØologiques, chose courante dans l'industrie pØ-trolire, mais insuffisamment dØveloppØe en hydrogØo-logie. On conclut que les travaux de recherche ultØrieurs devraient s'attacher à dØvelopper les modles de facis, à les comparer entre eux, et à mettre au point de nouvelles mØthodes d'essais in situ, comprenant les mØthodes gØo-physiques, capables de reconnaître la gØomØtrie et les propriØtØs des facis. La constitution d'un catalogue mondial de la gØomØtrie et des propriØtØs des facis aquifres, ainsi que des mØthodes de reconnaissance utilisØes pour arriver à la dØtermination de ces systmes, serait d'une grande importance pratique pour les applications.Resumen La heterogeneidad se puede manejar por medio de la definición de características homogØneas equivalentes, conocidas como promediar o tratando de describir la variabilidad espacia...

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Section: Heterogeneity and Numerical Modelingmentioning

confidence: 99%

Dealing with spatial heterogeneity

et al. 2005

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“…A numerical ground-water flow model was used to simulate flow under existing permitted withdrawal rates (568,700 ft 3 /day or 150 Mgal/day) and to define time-of-travel protection zones (Prickett and Lonnquist, 1971;McKee, Inc., 1982, 1985). Time-of-travel well-field protection zones have been used to regulate land use and to limit activities that could adversely affect the ambient quality of ground water near the Northwest well field.…”

Section: Vulnerability-assessment Uncertainties In the Northwest Wellmentioning

confidence: 99%

Assessing the Vulnerability of a Municipal Well Field to Contamination in a Karst Aquifer

Renken

Cunningham

Zygnerski

et al. 2005

Environmental and Engineering Geoscience

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Proposed expansion of extractive lime-rock mines near the Miami-Dade County Northwest well field and Everglades wetland areas has garnered intense scrutiny by government, public, environmental stakeholders, and the media because of concern that mining will increase the risk of pathogen contamination. Rock mines are excavated to the same depth as the well field's primary producing zone. The underlying karst Biscayne aquifer is a triple-porosity system characterized by (1) a matrix of interparticle porosity and separate vug porosity; (2) touching-vug porosity that forms preferred, stratiform passageways; and, less commonly, (3) conduit porosity formed by thin solution pipes, bedding-plane vugs, and cavernous vugs. Existing ground-water flow and particle tracking models do not provide adequate information regarding the ability of the aquifer to limit the advective movement of pathogens and other contaminants. Chemical transport and colloidal mobility properties have been delineated using conservative and microsphere-surrogate tracers for Cryptosporidium parvum. Forced-gradient tests were executed by introducing conservative tracers into injection wells located 100 m (328 ft) from a municipal-supply well. Apparent mean advective velocity between the wells is one to two orders of magnitude greater than previously measured. Touching-vug, stratiform flow zones are efficient pathways for tracer movement at the well field. The effective porosity for a continuum model between the point of injection and tracer recovery ranges from 2 to 4 percent and is an order of magnitude smaller than previously assumed. Existing well-field protection zones were established using porosity estimates based on specific yield. The effective, or kinematic, porosity of a Biscayne aquifer continuum model is lower than the total porosity, because high velocities occur along preferential flow paths that result in faster times of travel than can be represented with the ground-water flow equation. Tracer tests indicate that the relative ease of contaminant movement to municipal supply wells is much greater than previously considered.

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“…Numeric response models are presented by Freeze (1969), Neuman and Witherspoon (1971) and Prickett and Lonnquist (1971). Selected references on individual well design and construction methods are Johnson, Inc. (1966), Walton (1970) and Ahrens (1970).…”

Section: Previous Workmentioning

confidence: 99%

“…One procedure for controlling time increments is to let the first be equal to, for example, 100 seconds, and succeeding time increments increase by the factor 1.2 (Prickett and Lonnquist, 1971).…”

Section: Mathematical Definition Of Aquifer Response Modelmentioning

confidence: 99%

Minimizing costs in well field design in relation to aquifer models

Bostock¹,

Simpson²,

Roefs³

1977

Water Resources Research

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For a given production rate from a proposed well field, well construction and replacement costs decrease with fewer and larger wells spaced farther apart, while pumping lift costs increase. A method for minimizing the sum of these two costs uses a two‐dimensional uniform grid of wells to select a combination of well spacing and well capacity that minimizes costs for a given demand. Uncertainty in field permeability at future well sites is treated by averaging the possible outcomes over all wells in accord with a probability density function for permeability values. The method assumes an annual cycle whereby the water table declines owing to pumping in a dry season and is recharged to its initial state during a wet season.

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Modeling Techniques for Groundwater Evaluation

Cited by 68 publications

References 144 publications

Dealing with spatial heterogeneity

Dealing with spatial heterogeneity

Assessing the Vulnerability of a Municipal Well Field to Contamination in a Karst Aquifer

Minimizing costs in well field design in relation to aquifer models

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