Great Lakes Water Levels Rising To…Where?

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Sunset Inlet, Cape Hurd area – Toby in 1987.
Submitted by Daryl Cowell
Sunset Inlet, Cape Hurd area – Sam in 2013.
Sunset Inlet, Cape Hurd area – Cody in 2019.

The 2013 Sources of Knowledge Forum was titled “Challenges of a Changing Lake”. As you may recall, the Lake Huron Basin was approaching historical lows approximately one and a half meters below the earlier 1987 high of about 177.3 m. The 1987 high was the highest recorded since about 1885 when levels were approximately 10 cm higher (but not comparable due to changes in the gauge location). The Saugeen Conservation Authority sets the “flood level” at 177.6 m (a.k.a., “the black line”). The (locally) famous Comprehensive Zoning By-Law also establishes a 15 m set back from this line for building envelopes to account for wave up-rush (a.k.a., “the red line”).
We had purchased our property at Cape Hurd in 1986 and are very familiar with the ’87 high water level. It was exactly at the tree line and pretty much bang-on with the black line. We are also familiar with the low levels reached in 2013 when our adjacent cove (“Sunset Inlet”) was completely drained. As we now watch the level rising to, as of this spring, within about 20 cm or so of the 1987 high (based on a rough visual check) we have to ask the question: ”Where are lake levels going? Back to the 1987 high? Lower? Or…even higher?
Many of us who remember the 1987 high, and have been watching levels rise since 2013, might be thinking that this is simply a retracement of the old high. There is no reason that this should happen and we might all be surprised where it’s going.
At the time of the SOK Forum in 2013, the low water levels were receiving a great deal of attention as many cottages no longer had a view of the lake and docks where high and dry. Even the Cheech was scraping bottom. Given the high public interest of the time, The Lake Huron Centre for Coastal Conservation, located in Goderich, developed a position paper on lake levels. They presented at the 2013 SOK Forum and noted a number of factors affecting levels including precipitation, diversions of lake water out of the basin (e.g., Chicago River), dredging of channels to support shipping, and isostatic rebound following glaciation. Although they did not conclude any one actor was to blame, they did note that natural factors such as precipitation and evaporation outweigh man-induced factors. However, as we are always looking for a simple cause involving a perpetrator toward whom we can point our finger, I recall that the public consensus at the time was to blame dredging as the primary culprit, especially since the St. Clair River and Lake St. Clair had recently been dredged to maintain the St. Lawrence Seaway shipping channels.
The Great Lakes are glacially-scoured bedrock basins last shaped 14,000 or so year ago during the Wisconsin maximum. They are essentially big bathtubs that are oversized for their drainage basins and it was always my understanding that weather – precipitation and temperature where the primary driving forces to lake levels. High precipitation and cold winters caused lake levels to go up and dry conditions with warm winters resulted in them going down. The lakes have a large surface area-to-basin area ratio and if they don’t freeze to a significant extent, they become large evaporation pans over the winter. Rain and snowfall, particularly in the northern basins are critical.
I also presented at the 2013 SOK Forum and although I acknowledged Isostacy as a factor, I did not lay any blame on dredging works or at the diversions. Keep in mind, the Chicago diversion is countered by the Albany River diversion where water is directed into Lake Superior via Lake Nipigon to drive power plants on the Ogoki Reservoir.
At the time, I overlaid the annual precipitation records onto the graph of Lake Huron levels as well as the year the seaway was first dredged (1873) and the year the Chicago diversion was established (1900). No immediate or lasting lowerings were obvious following either of these events. However, the relationship between water levels and total annual precipitation is clear (see graph).
So where are water levels going next? Good question. There is nothing magical about the 1987 high. Although we intuitively judge that “climate warming” will lead to warmer and dryer conditions which should have a lowering affect, however, we should be talking of “climate change” not “warming”. As we have seen in recent years, historical record flooding has/is occurring to the west of us (Iowa, Nebraska) and to the east of us (Ottawa River, Montreal). These are occurring due to changes in our climate (probably man-caused) that is affecting storm patterns, frequencies and intensities that are derived in the Pacific and Gulf of Mexico. I will note that we live between Iowa and Ottawa and are clearly being affected by these systems. However, we have been buffered by the size of the lakes and have not seen property flooding during the post-2013 run-up. From that low to the current high is only 6 years. We are now nearing the historical high but there is no reason we should be unworrying and think it’s primed to start working its way lower.
If climate change continues to bring us cold winters (remember the vortex?) and heavy precipitation, there is no magic water level and there is no reason for the lakes to stop rising. I am not prognosticating here, but let’s not get too smug regarding our neighbours in Iowa or Ottawa…there is no law that says the red line won’t become the future black line…should make for some interesting Council meetings!
Daryl W. Cowell,
Tobermory

Note: Current lake levels can be found at: https://www.glerl.noaa.gov/data/wlevels/lowlevels/plot/MichHuron.jpg

Lake Huron Hydrography showing the relationship between water levels and total annual precipitation.