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|Title:||Leaky artesian aquifer conditions in Illinois|
|Author(s):||Walton, William Clarence|
Leaky artesian conditions exist in many parts of Illinois where aquifers are overlain by deposits or confining beds which impede or retard the vertical movement of ground water. Under leaky artesian conditions, the cone of depression developed by a pumping well is influenced by the vertical permeability of the confining bed in addition to the hydraulic properties and geohydrologic boundaries of the aquifer.
The vertical permeability of a confining bed often can be determined from the results of pumping tests by using the nonsteady-state leaky artesian aquifer equation derived by Hantush and Jacob (1955). A time-drawdown type curve method for analyzing pumping test data under nonsteady-state conditions is described in detail. A distancedrawdown type curve method for analyzing pumping test data under steady-state conditions devised by Jacob (1946) is also described. These two methods are applied to available pumping test data for Illinois. The results of a test made near the village of Dieterich in Effingham County are presented to illustrate the analysis of data. A summary of the leaky artesian test data collected to date indicates that the vertical permeability of glacial drift deposits in the southern half of Illinois ranges between 0.08 and 1.6 gallons per day (gpd) per square foot.
Effects of leakage closely resemble the effects of a recharge boundary if the effects of partial penetration are excluded. The data for the Dieterich pumping test are used to show that recognition of leaky artesian conditions is critically important in predicting the water supply potential of wells and aquifers.
A form of Darcy’s law is applied to data on the piezometric surface of the Cambrian-Ordovician Aquifer to determine the order of magnitude of the vertical permeability of the Maquoketa Formation. The Maquoketa Formation has a maximum thickness of about 250 feet, consists largely of beds of dolomitic shale, and confines water in the Cambrian-Ordovician Aquifer under artesian pressure. The Cambrian-Ordovician Aquifer is encountered at an average depth of 500 feet below the surface at Chicago, has an average thickness of 1000 feet, consists mainly of beds of sandstone and dolomite, and is the most highly developed source of large ground-water supplies in northeastern Illinois. Computations indicate that the average vertical permeability of the Maquoketa Formation in northeastern Illinois is about 0.00005 gpd per square foot. Leakage in 1958 through the Maquoketa Formation in northeastern Illinois is estimated to be about 8,400,000 gpd or about 11 per cent of the water pumped from deep wells.
|Publisher:||Illinois State Water Survey|
|Series/Report:||Illinois State Water Survey. Report of Investigation ; no. 39|
|Description:||Bibliography: p. 27.
Enumeration continues through succeeding title.
|Rights Information:||Copyright 1960 Board of Trustees of the University of Illinois|
|Date Available in IDEALS:||2018-11-15|
|Identifier in Online Catalog:||738654|