The real control on water levels is the elevation of the St. Mary’s Rapids; these rapids form the main control on minimum and maximum lake levels.

Factors such as snow melt, precipitation and seasonal temperature drive the annual rise and fall of the lake. Short term factors such as strong winds and storms can create a “seche” which resembles the tides found in the oceans. Elevations during these storm events can differ from one side of the lake to the other by over a metre during these short term weather events. The International Joint Commission (IJC) regulates the water level on Lake Superior and has a goal of maintaining the 183.4 long time average water level.