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Title

  • Selected analytical methods for well and aquifer evaluation

Description

  • The practical application of selected analytical methods to well and aquifer evaluation problems in Illinois is described in this report. The subject matter includes formulas and methods used to quantitatively appraise the geohydrologic parameters affecting the water-yielding capacity of wells and aquifers and formulas and methods used to quantitatively appraise the response of wells and aquifers to heavy pumping. Numerous illustrative examples of analyses based on actual field data are presented. The aquifer test is one of the most useful tools available to hydrologists. Analysis of aquifer test data to determine the hydraulic properties of aquifers and confining beds under nonleaky artesian, leaky artesian, water table, partial penetration, and geohydrologic boundary conditions is discussed and limitations of various methods of analysis are reviewed. Hydraulic properties also are estimated with specific-capacity data and maps of the water table or piezometric surface. The role of individual units of multiunit aquifers is appraised by statistical analysis of specific capacity data. The influence of geohydrologic boundaries on the yields of wells and aquifers is determined by means of the image-well theory. The image-well theory is applied to multiple boundary conditions by taking into consideration successive reflections on the boundaries. Several methods for evaluating recharge rates involving flow-net analysis and hydrologic and groundwater budgets are described in detail. Well loss in production wells is appraised with step-drawdown test data, and well screens and artificial packs are designed based on the mechanical analysis of the aquifer. Optimum well spacings are estimated taking into consideration aquifer characteristics and economics. Emphasis is placed on the quantitative evaluation of the practical sustained yields of wells and aquifers by available analytical methods. The actual groundwater condition is simulated by a model aquifer having straight-line boundaries, an effective width, length, and thickness, and sometimes a confining bed with an effective thickness. The hydraulic properties of the model aquifer and its confining bed, if present, the image-well theory, and appropriate groundwater formulas are used to construct a mathematical model that provides a means of evaluating the performance of wells and aquifers. Records of past pumpage and water levels establish the validity of this mechanism as a model of the response of an aquifer to heavy pumping.


Originally Deposited as: 999999992049

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Language(s): EN-English

Volume or Year: 1962
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Date Created: 9 24 2004
Date Last Modified: 5 13 2003

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1. Selected analytical methods for well and aquifer evaluation (20060927190115_ISWSB-49.pdf).
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