Comparison of Hydrologic Data from Monroe County, Michigan, 1991-2001

In the summer of 2001, there were renewed concerns about the effects of quarry dewatering on nearby domestic ground-water supplies in Monroe County, Michigan. Reports of domestic wells “going dry” are not uncommon historically in Monroe County. Such reports have been linked to droughts, nearby irrigation, quarrying, and other large ground-water uses since as early as 1900 (Sherzer, 1900). Concerns about ground-water availability during the short, but extreme, drought of 1988 prompted the County and the State of Michigan to cooperate with the USGS (U.S. Geological Survey) on a county water resources assessment during the early 1990s (Nicholas and others, 1996).

Aquifers in Monroe County generally yield sufficient water for domestic supplies. High transmissivities and low storage in fractured carbonate aquifers and poor water quality at depth (Nicholas and others, 1996), however, make domestic supplies very susceptible to the effects of drought and large withdrawals. Therefore, there are legitimate concerns about sustainable groundwater supplies in the County.

Additionally, significant increases in ground-water uses in Monroe County during the past decade coincide with very dry years during the late 1990s. Although ground-water-level data were collected by Monroe County during the last decade, there are not comparable data sets available for many water uses. Therefore, determining whether concerns about domestic wells going dry can be linked to ground-water withdrawals or climate is problematic.

In response to recent concerns, the USGS and MDEQ (Michigan Department of Environmental Quality) entered into a cooperative agreement in October 2001 to conduct a study regarding the availability of ground water in Monroe County. The major goal of this study is to determine how widespread are the impacts of quarry dewatering operations.

This report summarizes the initial phase of the study which consists of a comparison of hydrologic data from 1991 to 2001. The 1991 data are reported by the USGS in the report by Nicholas and others (1996). Later data come from a variety of sources including USGS, MDEQ, Monroe County, National Oceanic and Atmospheric Administration, U.S. Army Corps of Engineers, and ground-water users. All non-USGS data in this report are given as reported; data verification was not a part of this initial phase. The types of data chosen for comparison in this report include water levels of Lake Erie, precipitation at Monroe, streamflow in the River Raisin at Manchester, ground-water use, ground-water levels, and ground-water quality.

The authors acknowledge the cooperation and provision of data and information by several agencies. Ground-water use for irrigation was provided by Ron Van Til of MDEQ. Quarry discharges were provided by Jennifer Rogers of MDEQ. Ground-water-level data for 1993 to 2001 were provided by the Monroe County Health Department. The authors also acknowledge Carlos Hernandez, Chris Hoard, Tom Morgan, Tom Sabin, and Dave Westjohn for collecting streamflow, ground-water, and ground-water-quality data in autumn, 2001. Sharon Baltusis and Jaye Lunsford assisted in the compilation and presentation of hydrologic data in this report.