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<br />DESCRIPTION OF THE MODEL <br />U40ihe computer model used in this study is an iterative alternating- <br /> <br />direction implicit finite-difference ground-water model (Trescott, 1973) <br /> <br />used widely by the U.S. Geological Survey. The model solves a finite- <br /> <br />.. <br /> <br />difference approximation' of the differential ground-water flow equations. <br /> <br />The data necessary for this study included initial altitude of water <br /> <br />table, aquifer hydraulic conductivity, altitude of bedrock, altitude of <br /> <br />land surface, and a definition of model boundaries. The model uses <br /> <br />discrete points of data in its computation; therefore, a grid system was <br /> <br />constructed to overlay maps of each of the above-mentioned data. The <br /> <br />altitudes of the water table and bedrock for this study were taken from <br /> <br />reports published by the U.S. Geological Survey (Burr and others, 1972a, <br /> <br />1972b). The values of hydraulic conductivity, which varied between <br /> <br />1.7 ft/d (0.53 mid) and 1,700 ftld (530 mid) were computed from trans- <br /> <br />missivity and saturated thickness maps from the same reports. Altitude <br /> <br />of land surface was taken from U.S. Geological Survey quadrangle maps. <br /> <br />;; <br />