Water levels in the Great Lakes obviously have their ups and downs over the years, as any lakeshore resident can tell you. There has been the appearance of longer-term trends within these ups and downs, where lower-than-average levels can dominate for several consecutive years, followed by several years in which higher levels dominate.
Having perused lake level records compiled by the Army Corps of Engineers as well as Canadian data going back to 1918, I can tell you these seemingly regular cycles are not so regular. (There is also some evidence their peaks may be increasing due to more frequent heavy precipitation events in and near the Great Lakes, tied to climate change.)
Click here to see where we are as of this past week. The second line down on the chart toward the bottom, chart datum, is the average level in feet. The next line down shows the difference in inches from long-term chart datum recently. You can look to the Sept. 11 line and find levels had dropped a few inches. If you drop to the Oct. 11 line, you’ll see levels have come back up and — most importantly — that the difference between the current levels and long-term October mean chart datum, on all five lakes, is substantial.
Lakes Michigan and Huron are thought of hydrologically as one lake because they are broadly joined. Michigan-Huron and Lake Erie are well above average in inches for October. The increased evaporation that occurs in the warm months into early autumn typically lessens these differences. This year, the fairly wet September locally and across the lakes clearly has not helped matters.
Of the five lakes, Lakes Superior and Ontario are the least above-average, at plus-14 and plus-18 inches respectively. Heading into mid-autumn, these anomalies (and plus-33 inches on Michigan-Huron, along with plus-27 inches on Erie) do not portend well for the remainder of this year and at least the first half of next year. The Great Lakes region and the north central United States are already rather wet, even after summer warming and evaporation.
There isn’t much forecast skill demonstrated in seasonal outlooks for precipitation, except when certain variables are in a very amplified state, such as a strong El Niño. That is not the case this autumn, when most indicators are pointing to near-neutral conditions in the El Niño southern oscillation. Most other signals from nature are fairly weak at this time, so it may be a fair assumption to go with more average winter season precipitation across the northern states for lack of a better signal.
With that in mind, the Army Corps' long-term lake-level forecasts, starting out with well-above (but not quite record) average levels, cannot be optimistic for substantial reductions in those levels. If an unexpected dry spell developed and persisted across the north central and Great Lakes states this winter and early next spring, that would change, but no such indicator is now present. Here is the Corps’ long term forecast for Lake Superior. The black dots represent average chart datum.
If you’re new to this topic, Lake Superior and all Great Lakes levels are related to lake levels in eastern Lake Erie and Lake Ontario. That excess flow eventually drains from Michigan-Huron through Lake St. Clair into Lake Erie, and that flow, of course, goes down the Niagara River to Lake Ontario. So, if Lake Superior is well above average, its high level affects us as well.
Here is the Michigan-Huron forecast. Green Bay, Wis., is running a huge precipitation anomaly of plus 17 inches for the year. Milwaukee is plus 11 inches; Marquette, Mich., is plus 10 inches; and Muskegon, Mich., is plus 12 inches. It's been very wet over the central and western Great Lakes.
The renewed surge upward in the spring on all the lakes is tied to snow melt and drainage in addition to winter and early spring precipitation.
We needed to be off to a better start with near-average lake levels in mid-October to have any hope of real improvement for next year. Keith Kompoltowicz, chief of watershed hydrology at the Army Corps headquarters in Detroit, is forecasting Michigan-Huron to be around 11 inches higher in January 2020 than it was this past January.
As he pointed out to USA Today: “Lake Superior, Lake St. Clair, Lake Erie and Lake Ontario set new record high water levels over the summer, with lakes Michigan and Huron an inch or less off their 100-year highs. In July, lakes Erie and Ontario broke their monthly records by more than 4 inches.”
In addition, if we were again to have an excessively wet spring, as occurred last spring, the situation would worsen beyond these pessimistic forecasts. There is no way to predict one way or another how next spring’s precipitation will go. But if it is wetter than average, it will be the fourth consecutive such spring.
Current outflows down the Niagara River and out of Lake Ontario into the St. Lawrence River are running well above average. The control measure at that point for Lake Ontario has real limitations on how much mitigation it can provide, especially when the entire Great Lakes system is loaded at these levels.
Sadly, the idea that this eastern Lake Ontario-controlled outflow can make a dramatic difference in this situation is an engineering fantasy, despite the understandable anger and frustration of Lake Ontario shoreline residents. The public and political controversies surrounding the 2014 change in regulations and triggers for outflow are not well-based in the engineering and hydrological science. The following NOAA illustration for what led to the record flooding of 2017 is a graphic explanation of the main factors that were involved:
The box in the lower left of this graphic is a huge part of the story; that is, the inflow from the other four well-above-average lakes. The very large outflow now going into the St. Lawrence river is generally overwhelmed by nature’s vast excess water volume upstream inexorably flowing downstream. Later in the cold weather season, additional complications will be caused by ice buildup on the Ottawa River and the Lake Ontario-St. Lawrence River systems. At certain times during ice buildups, the outflow will need to be temporarily reduced to lessen flooding downstream.
The science shows no lawsuit against the International Joint Commission can change this. It’s a bad situation for lakeshore property dwellers.