Lake Level Variations. Water levels in the Great Lakes are also subject to periodic changes.
Records of lake levels dating from 1836 reveal seasonal and annual changes, which are due to variations
in precipitation annually, and from year to year. Lake levels (particularly Ontario and Superior) are also
partially controlled by regulatory works operated jointly by Canadian and U. S. authorities, and these
may result in minimizing lake level changes. Average monthly lake level elevations showing data for the
past calendar year and present year to date, and a forecast for the next six months, are published monthly
by the U. S. Army Corps of Engineers, Detroit District (see Other Help Section).
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