How has dredging in the St. Clair River affected the upper Great Lakes?
• In the past 150 years, the flow capacity of the St. Clair River has been altered by dredging more than any other factor. • Dredging in the St. Clair River for navigation began in the late 1850s. The largest dredging occurred between 1933 and 1936. The last major dredging took place between 1960 and 1962. Since 1962, all dredging in the St. Clair River has been to maintain the channel to its authorized depth of 8.2 metres (27 feet) to allow clearance for ships as part of the St. Lawrence Seaway system. • The increase in conveyance capacity of the St. Clair River due to dredging has reduced the difference in levels between Lake Huron and Lake Erie. This has permanently lowered the levels of lakes Michigan and Huron. Based on the current regulation plan, lower levels on lakes Michigan and Huron have also resulted in higher outflow from Lake Superior. • The governments of the United States and Canada agreed to construct compensating works in the St. Clair River in response to water level
