Charles Avery 1995 <p>Abundant water resources have been an important part of the economic development of the Chicago area for more than a century. The city of Chicago, Ill., and other&nbsp;lakefront towns have used Lake Michigan as a water supply. Where water from Lake Michigan was not available or a need for supplemental water supplies was present, deep wells (generally greater than 700 feet) provided a clean, reliable, and abundant water supply&nbsp;from the Cambrian-Ordovician aquifer. Public water suppliers withdraw the most ground water in the eight-county Chicago area (Cook, Du Page, Grundy, Kane, Kendall, Lake, McHenry, and Will Counties). This report describes a reversal in the trend of declining ground-water levels in the Cambrian-Ordovician aquifer in the Chicago area as public water suppliers have converted from the withdrawal of ground water from wells to the withdrawal of surface water from Lake Michigan.</p> application/pdf 10.3133/fs22295 en U.S. Geological Survey Reversal of declining ground-water levels in the Chicago area reports