The outflows from two of the five Great Lakes (Lake Superior and Lake Ontario) are regulated by control structures. These outflows are varied in accordance with their respective regulation plans.
The outflows from Lakes Michigan-Huron and Erie are not regulated, but rather, are controlled exclusively by the hydraulic characteristics of their outlet rivers.
Outflows from Lake Superior are regulated near the twin cities of Sault Ste. Marie, Michigan and Ontario. Outflows are controlled by three hydropower plants and a 16-gate control structure called the Compensating Works. The outflow is established on a monthly basis by the International Lake Superior Board of Control (ILSBC). The outflow is set in accordance with the current regulation plan, Plan 2012.
Outflows from Lake Ontario are established on a weekly basis by the International Lake Ontario-St. Lawrence River Board (ILOSLRB). The principle control structure is the Moses Saunders Dam. The Lake Ontario outflow is set in accordance with the current regulation plan, Plan 2014.