Changes in Chloride Concentration in Water from Municipal Wells That Tap Aquifersin Rocks of Cambrian and Ordovician Age in Northeastern Illinois, 1915-84

摘要

In the late 1970's, the U.S. Geological Survey (USGS) initiated the RegionalAquifer-System Analysis (RASA) to study regional aquifer systems throughout the United States. The general goals of a RASA investigation are to evaluate each aquifer's water-supply potential and water quality, and, using computer models of the ground-water flow system, to provide a means for evaluating aquifer response to stresses placed on the flow system. The report describes the location, magnitude, and causes of the changes in chloride concentration in the aquifers in the Cambrian and Ordovician Systems in a six-county area of northeastern Illinois. The report includes stratigraphic columns, maps, and graphs that show the geology and hydrogeology of the study area and the changes in chloride concentration in water from wells that tap the aquifers in the Cambrian and Ordovician Systems. The geologic and hydrogeologic nomenclature used in the report is that used by Visocky and others (1985) and does not necessarily follow the usage of the USGS.