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Hydrogeology of Huron County, Michigan, 1991

By: Sweat, M.J.


Huron County is a mostly agricultural county of 36,000 residents, and is located in east-central Michigan. Inland surface waters of the county are not reliable sources of water supply. The Napoleon Sandstone Member of the Marshall Formation is the source of most groundwater used in Huron County. Sandstones in the lower part of the Marshall Formation are used as a source of groundwater where the Napoleon Sandstone Member is absent; the only alternative sources of groundwater are surficial deposits. Surficial deposits are primarily till, glacial and lacustrine clay, and lenses of sand and gravel. Water levels and quality in the surficial deposits are susceptible to seasonal change. Pesticides were present in water from two wells sampled during this study. The predominant dissolved ions in groundwater from the Napoleon Sandstone Member are calcium and bicarbonate. Groundwater recharge may be occurring in the south-central part of the county to surficial and bedrock aquifers. The absence of tritium in the groundwater indicates that residence time of water now in the flow system is greater than 40 years. Groundwater flow in the county is from southeast to northwest toward Saginaw Bay. The Michigan Formation and Coldwater Shale act as confining units, and the Saginaw and Michigan Formations limit the rate of recharge to the Marshall Formation. Horizontal hydraulic conductivities of the Napoleon Sandstone Member and sandstones in the lower part of the Marshall Formation in Huron County range from 0.25 to 1.5 ft/day, and transmissivities range from 7 to 50 cu ft/day/sq ft times foot of aquifer thickness. Horizontal hydraulic conductivities in overlying deposits are 2 and 3 orders of magnitude less than horizontal hydraulic conductivities in the Marshall Formation. (Lantz-PTT)

RECORD ID: 9302674

F&G CODE: 02f; 06d

Sweat, M.J., 1991, Hydrogeology of Huron County, Michigan: U.S. Geological Survey Water-Resources Investigations Report 91-4133, 76 p.

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