How is the Lake Michigan water level determined?
The water levels are still-water surface elevations over the entire lake
surface. Water levels at specific locations may differ substantially due to
meteorological influences. Official records are based on monthly average
water levels and not daily water levels. The current high water levels are
expected to persist for at least the next six months, so flood-prone areas
should remain vulnerable. Lake Michigan and Lake Huron are considered to be
hydrologically one body of water connected by the Straits of Mackinac, so
the current near-record high Lake Michigan water levels also apply to Lake
Huron. All lake levels for the 1918-2019 period are referenced to the
International Great Lakes Datum of 1985 and have coordinated with Canada.