Managing Warming Waters on the Great Lakes and St. Lawrence Seaway

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The binational governing body that oversees the Great Lakes and St. Lawrence Seaway, the International Joint Commission (IJC) recently hosted presentations to address issues related to warming water. Two issues have recently emerged and both are believed to be the result of climate change, with water temperature rising faster in Lake Superior than in any other northern lake at comparable latitude, in the world. Rising water levels along the St. Lawrence Seaway are also believed to be the result of climate change.


A population of 60 million people lives in jurisdictions surrounding North America’s Great Lakes and along the St. Lawrence Seaway. While a single navigation lock separates Lake Superior to the other Upper Great Lakes located upstream of Niagara Falls, some 7,000 ships transit through the lock annually carrying some 86 million tons of mainly bulk freight valued at around $23 billion. Several large cities that include Chicago, Milwaukee, Detroit, Cleveland, Windsor, Buffalo, Hamilton and Toronto depend on the Great Lakes to provide potable water for a population of around 20 million people at a time when water quality is becoming a cause of concern.

During recent presentations, the International Joint Commission and its subsidiary body the International St. Lawrence River Board of Control focused on rising water levels along the waterway located upstream of Montreal. Participants living along the Upper St. Lawrence River between Montreal and Lake Ontario along with participants living around Lake Ontario raised the alarm bells over high water levels during both 2018 and early 2019. Even participants representing regions located upstream of Lake Erie expressed concern over higher than usual water levels around Lake Huron and Georgian Bay.

Toxic algae

While phytoplankton will appear in large bodies of water, one particular strain of phytoplankton called cyanobacteria or blue-green algae is problematic. It is toxic to animal and human health and outbreaks of blue-green algae have recently occurred on both Lake Erie and Lake Superior. While the flow of phosphates into Lake Superior is relatively low, it is the fastest warming large northern lake and warmer temperature supports the emergence of blue-green algae. While water tests have revealed the presence of low levels of phosphorous in Lake Superior, runoff from urban gardens has been suggested as a possible source.

Phosphorous levels are higher in Lake Erie where outbreaks of blue-green algae have recently occurred, with the presence of cattle and dairy farms located along rivers that feed into the lake being identified as a possible source. There is also much agriculture located along rivers that feed into Lakes Michigan and Huron, with farm run-off containing phosphates and nitrates that flow into Lake Erie. While it is outside the scope of the IJC to remedy the flow of fertilizer runoff and other farm runoff into the Great Lakes, other regulatory bodies will need to remedy the issue.

Water levels

Between late 2016 and late 2019, extremely high water levels occurred across Lake Ontario and along the Upper St. Lawrence River, to the point where waterfront properties were flooded for extended durations. While 2020 spring flood levels were manageable, water levels were still high and declined to just above seasonal average levels by late summer of 2020. Officials at IJC have expressed concerns about possible elevated water levels during early 2021.

As a result, the commission plans to increase outflows of water from Lake Ontario into the Lower St. Lawrence River as a future flood preventative measure. Present water levels at Montreal and downstream along the Lower St. Lawrence River are sufficiently low so as to allow for some additional transfer of water from Lake Ontario. During earlier presentations, one of the commission members theorized that “as a result of climate change, elevated water levels along the lower Great Lakes and Upper St. Lawrence River might be the new normal!”


The binational governing body that has responsibility over the Great Lakes and Seaway has to deal with a combination of serious problems that includes a warmer Lake Superior, higher water levels in Lake Ontario and the Upper St. Lawrence River, and the appearance of toxic blue-green algae (cyanobacteria) on Lake Superior and Lake Erie. Other agencies have jurisdiction over the rivers and streams that flow into the Great Lakes and that carry farm run-off into the lakes. The International Joint Commission will need to reach out to these other outside agencies about seeking to resolve the problems.

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