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St. Clair River Results

Findings & Recommendations:

On December 15, 2009, the IUGLS released the report Impacts on Upper Great Lakes Water Levels: St. Clair River.  This report reflects peer review and public comment on a draft report released on May 1, 2009, as well as additional research and analysis.  After nearly two years of study that engaged nearly 100 scientists and engineers, with extensive input from independent peer reviewers and the public, the International Upper Great Lakes Study Board found that:

  • There has been no significant erosion of the channel in the upper reach of the St. Clair River bed since at least 2000;
  • An increase in the river's conveyance capacity accounts for 7 to 14 cm (2.8 to 5.5 inches) of the decline in head difference between Lake Michigan, Huron and Lake Erie from 1963 to 2006; however, this change is not ongoing and there has been a slight decrease in conveyance capacity since 2000;
  • Climate is the main driver of lake level relationships over time and accounts for 9 to 17 cm (3.5 to 6.7 inches) of the decline in head difference. In particular, hydroclimatic change contributed to a substantial decline in net water supplies to Lake Michigan, Huron in the most recent decade;
  • The difference in water levels between Lake Michigan, Huron and Lake Erie (head difference) declined on average by about 23 cm (9 inches) between 1963 and 2006; and
  • Shifts in the earth's crust as it continues to adjust to the retreat of glaciers account for 4 to 5 cm (1.6 to 2 inches) of the decline in head difference with the apparent resulting decrease in water levels being more pronounced in the Georgian Bay region of eastern Lake Huron.

The IUGLS Study Board did not recommend remedial measures in the St. Clair River at the time of this Study but did recommend that the next phase of the Study (Lake Superior) examine whether mitigative measures in the St. Clair River might be necessary based on its assessment of the potential future impacts of climate change on upper Great Lakes levels. The Board also recommended that the governments of Canada and the U.S. undertake cooperative efforts to improve the monitoring and  analysis of Great Lakes water supplies and connecting channel flows.