|PUBLICATIONS—Scientific Investigations Report|
U.S. Department of the Interior
U.S. Geological Survey
Prepared in cooperation with the Chippewa Township, Isabella County, Michigan
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The ground-water resource potential of Chippewa Township, Isabella County, Mich. was characterized on the basis of existing hydrogeologic data, water-level records, analyses of water samples, and interpretation of geophysical survey data. Eight ground-water samples were collected and analyzed for major ions, nutrients, and trace-metal composition. In addition, 10 direct current-resistivity soundings were collected throughout Chippewa and Coe Townships to identify potential freshwater in the aquifer system. The aquifer system includes complexly interbedded glaciofluvial, glaciolacustrine, and basal-lodgment tills, which overlie Jurassic or Pennsylvanian sedimentary rocks. In parts of the township, freshwater is present in all geologic units, but in most areas saline water is encountered near the base of Pleistocene glacial deposits and in the Jurassic or Pennsylvanian bedrock. A near-surface sheet of relatively dense basal-lodgment till likely prevents, or substantially retards, significant direct recharge of ground water to glacial and bedrock aquifers in Chippewa and adjacent townships.
Glacial sands and gravels form the principal aquifer for domestic wells (97.5 percent of wells in the township). The single community water supply in the township has wells screened in glacial deposits near the base of the glacial drift. Increased withdrawals of ground water in response to increasing demand has led to a slight decline in water quality from this supply. This water-quality decline is related primarily to an increase of dissolved sulfate, which is probably a function of well depth and dissolution of gypsum, a common mineral constituent in the Jurassic “red beds” , which form the uppermost bedrock unit throughout most of the township. One explanation for the increase in sulfate is upconing of saline water from bedrock sources, which may contain saline water.
Westjohn, D.B. and Hoard, C.J., 2006, Hydrogeology and Ground-Water Quality, Chippewa Township, Isabella County, Michigan, 2002-05: U.S. Geological Survey Scientific Investigations Report 2006-5193, 27 p. Date Posted: December 11, 2006:
Purpose and Scope
Ground-Water Quality in Glacial and Bedrock Aquifers
Appendix A—Logarithmic plots of modeled DC-resistivity soundings
1. Map showing nine-township subregional study area, Isabella and Midland Counties, Mich
2. Map showing glacial landforms, the Gladwin Moraine, and sediment types in the study area
3. Graph showing distribution of wells by depth, Chippewa Township, Isabella County, Mich. Wells at depths equal to and greater than 320 feet are completed in bedrock
4. Map showing distribution of bedrock underlying glacial deposits in the study area
5. Map showing location of wells that were monitored for water levels and wells sampled for water quality
6. Graphs showing water levels measured in selected wells at the Isabella Reservation, and precipitation measured at the Pioneer/Dupont Agriculture and Nutrition Research Station, Ithaca, Mich
7-9. Maps showing—
7. Configuration of the composite potentiometric surface of ground water in glacial deposits, based on static water levels recorded on drillers’ logs
8. Topography and surface-water drainage features in the study area
9. Configuration of the composite potentiometric surface of ground water in bedrock units
10. Piper diagram illustrating water-chemistry of 15 ground-water samples from the study area
1. Physical and chemical characteristics for 15 water samples from wells in Isabella County, Mich
For additional information, contact:
U.S. Geological Survey
Michigan Water Science Center
6520 Mercantile Way, Suite 5
Lansing, MI 48911-5991
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