Lake Michigan is a navigable waterway, but it is the only Great Lake which is not also an international waterway. The bed of Lake Michigan is owned by the four states which share its shoreline: Wisconsin, Illinois, Indiana, and Michigan. Indiana holds the portion of Lake Michigan within its borders in trust for our citizens, but this trust is subject to the federal navigational servitude. Lake Michigan and its navigable tributaries are referenced in Navigable Waterways Roster.

The dividing line on Lake Michigan and other navigable waterways between public and private ownership is the ordinary high watermark. In general terms, "ordinary high watermark" (OHW) has been defined to be the line on the shore of a waterway that is

1. established by the Fluctuations of water; and
2. indicated by physical characteristics such as a clear and natural line impressed on the bank, shelving, changes in the character of the soil, the destruction of terrestrial vegetation, or the presence of litter or debris.

For Lake Michigan, both the U.S. Army Corps of Engineers and the Indiana Natural Resources Commission have recognized the ordinary high watermark to be at elevation 581.5 feet, International Great Lakes Datum (1985). The Commission has established the elevation of the OHW for the Indiana shoreline of Lake Michigan by rule at 312 IAC 1-1-26.

Although the actual elevation of Lake Michigan fluctuates, the elevation of the ordinary high watermark is fixed. The OHW is significant to many permitting activities, questions of ownership, and commercial and recreational boating usage. Regulatory authority may be referenced to the OWM, but there are instances when authority extends outside the OHW. For example, boating laws and fishing laws are enforced outside the boundaries of the OHW when the lake is high.

 

While the elevation of the OHW does not change, the physical location of the OHW moves with the erosion and deposit (called "accretion") of sand along the shoreline due to natural causes. Ownership can move as the line moves.