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Use of isotopes to identify sources of ground water, estimate ground-water-flow rates, and assess aquifer vulnerability in the Calumet Region of northwestern Indiana and northeastern Illinois

Water-Resources Investigations Report 2002-4213

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Abstract

Isotope data collected in the Calumet Region of northwestern Indiana and north- eastern Illinois, one of the most heavily industrialized regions of the United States, indicated that water in the surficial Calumet aquifer is well mixed. The Calumet aquifer is recharged areally by precipitation and locally may be recharged by surface water. The residence time of ground water in the Calumet aquifer is approximately 5 to 15 years. Ground-water-flow rates through the Calumet aquifer are estimated to be 400 to 2,300 feet per year. The permeable deposits, shallow water table, lack of an overlying confining unit, and proximity to numerous contaminant sources indicate that the Calumet aquifer is vulnerable to contamination. Isotopic data indicate that ground water in the confining unit underlying the Calumet aquifer is derived from a variety of sources that include Lake Michigan, modern precipitation, and discharge from the basal Silurian-Devonian bedrock aquifer. The source and apparent age of the water are variable and appear to be affected locally by various geologic and hydraulic factors. The vertical ground-water-flow rate through the unweathered part of the confining unit is about 0.20 feet per year and is about 6.3 feet per year through the weathered part. The data indicate the weathered part of the confining unit may be more vulnerable to contamination than the unweathered confining unit. Ground water in the basal Silurian- Devonian aquifer is derived from Lake Michigan, glacial-age water, and modern precipitation. Post-1952 recharge has occurred in the vicinity of Stony Island, Ill. Ground-water recharge of the Silurian-Devonian aquifer may be occurring near Calumet Harbor. The Silurian-Devonian aquifer is vulnerable to contamination where the confining unit is thin or absent or where the integrity of the confining unit has been compromised.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Use of isotopes to identify sources of ground water, estimate ground-water-flow rates, and assess aquifer vulnerability in the Calumet Region of northwestern Indiana and northeastern Illinois
Series title:
Water-Resources Investigations Report
Series number:
2002-4213
Edition:
-
Year Published:
2002
Language:
ENGLISH
Description:
v, 60 p. : ill., maps ; 28 cm.