Evaluating wells and aquifers by analytical methods

Abstract

The practical application of available analytical methods to ground-water resource management problems in Illinois is described in this report. The actual ground-water 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, the image-well theory, and ground-water formulas are used to construct a mathematical model which 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. For demonstration of the applicability of model aquifers and mathematical models, case histories of ground-water development in the Chicago region in northeastern Illinois and the Arcola, Taylorville, Tallula, Assumption, and Pekin areas in central Illinois are described. The model aquifers for the study areas range from a semi-infinite rectilinear strip of sandstones and dolomites 84 miles wide and 1000 feet thick to a semi-infinite rectilinear strip of sand and gravel 300 feet wide and 3.5 feet thick. Practical sustained yields of the aquifers range from 46 million gallons per day to 16,000 gallons per day.