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Fluctuations in Great Lakes water levels have occurred continually since the Great Lakes formed at the end of the Ice Age. Lake levels can affect the extent of shoreline erosion and shoreline property damage, riparian interests (beach widths and public access), dredging and shipping (depth of navigation channels), construction of marinas and other water dependent facilities, drinking water intakes, cooling water intakes for steel mills and electric generating stations, wetland acreage, and coastal flooding. Lake level records have been kept for "Lake Michigan/Huron" at various gage stations around these lakes since 1860. The "monthly average" lake levels presented below cover only the time period from 1918 to present.
The water levels presented below are obtained by "averaging" the recorded water levels of a representative network of gages located around both Lake Michigan and Lake Huron. This is done because Lake Michigan/Huron is hydraulically considered to be one body of water, connected by the Straits of Mackinac at the north end of the two lakes.
The "lowest" monthly average lake level for the representative network of gages on Lake Michigan/Huron, 576.05 feet IGLD 1985 International Great Lakes Datum, occurred in March 1964. The "highest" monthly average lake level for the network of gages, 582.35 feet IGLD 1985, occurred in October 1986. This is a difference of 6.30 feet in water level elevation since records have been kept.
If you look at the monthly averages of each of the "individual" gage stations around the two lakes, the all time "highest monthly average" lake level for a gage station, 582.64 feet IGLD 1985, occurred on Lake Huron at the Harbor Beach, Michigan gage in June 1886.
Expected Lake Level This Week:
If you are interested in the "expected lake level" for this week, go to the following Detroit Corps of Engineers web site, and under the topic "Water Level Forecasts" click on "weekly". http://www.lre.usace.army.mil/Missions/GreatLakesInformation/GreatLakesWaterLevels/WaterLevelForecast.aspx
This provides a "weekly data summary" of the representative gage stations around Lake Michigan/Huron and gives an estimate of the present lake level for the week. While this information is very preliminary, this "expected lake level" might be used as a "reference elevation" to estimate where the "Ordinary High Watermark (OHW)" elevation of State jurisdiction is located on the beach face.
The Ordinary High Watermark is used in Indiana to define the separation between private ownership above, and public ownership (State property) below the OHW on the beach. The OHW elevation is used for regulatory (State permitting) and public access determinations.
Lake Michigan Lake Levels (Graphs and Tables)