November 22, 2019
By Adam Bechle, Coastal Engineering Outreach Specialist, Wisconsin Sea Grant
The water levels on all the Great Lakes remain high, with every lake within seven inches of it’s record high water level for the month of November. A wet October saw precipitation that was was 46% above average across the Great Lakes.
Here are five things to know about water levels on Lake Michigan for November 2019.
What are the current water levels on Lake Michigan?
The water level of Lake Michigan as of November 22nd, 2019 is at an elevation of 581.50 feet above sea level (from the International Great Lakes Datum). To put this level into perspective, here are some statistics for Lake Michigan relative to the period of water level records measured from 1918 to 2018: (statistics from U.S. Army Corps of Engineers Weekly Water Level Update)
|Compared to…||Current Water Levels are…|
|One month ago||2 inches lower|
|One year ago||16 inches higher|
|Average November (from 1918 to 2018)||33 inches higher|
|Record November monthly mean (set in 1986)||6 inches below|
|Record high for any month (set in October 1986)||10 inches below|
What is the outlook for future water levels?
The US Army Corps of Engineers projects higher than average water levels to persist over the next several months for Lakes Michigan-Huron (see six-month forecast issued for November 2019 below). With water levels at near-record high levels already, the forecast indicates a high likelihood of record or near-record water levels again in 2020.
Water levels are in the midst of their their seasonal decline, with a projected drop of about 2 inches by December 25th, 2019. This decrease in water levels is expected throughout the winter as precipitation and runoff into the lakes typically decreases and evaporation from the lakes increases. In an average year, water levels vary seasonally by about one foot from a peak in summer to a low in winter, though every year is different. Water levels would be expected to begin a seasonal rise again next spring when runoff and precipitation increase.
Why are lake levels so high?
The story of Great Lakes water level changes is told by Net Basin Supply. Net Basin Supply accounts for water going into a lake in the form of precipitation and runoff minus water leaving a lake due to evaporation of water from the lake surface. In general, when Net Basin Supply is positive, more water enters the lake than leaves, yielding a rise in lake levels. Over the last five years, Net Basin Supply has been consistently positive, driving all the Great Lakes to rise. This is shown in the graph below, where blue indicates a positive Net Basin Supply and red is a negative Net Basin Supply – note there’s a lot more blue than red.
Lakes Michigan-Huron saw a positive Net Basin Supply in October 2019, in part due to the month’s above average precipitation (57% above average).
What would make water levels go down?
The historic record shows that water levels in the Great Lakes rise and fall with changes in precipitation and evaporation, so we know our high water levels will not be around forever. But what are the perfect conditions that would help water levels go down sooner rather than later? According to Keith Kompoltowicz, chief of watershed hydrology at the U.S. Army Corps of Engineers’ Detroit district “A cool, dry fall would evaporate water from the lakes because the lakes are relatively warm. As we move into the winter, we don’t want a healthy snowpack. We want a warm, snowless winter followed by a warm, dry spring.” Those would be the ideal conditions – low precipitation and runoff with high evaporation – to get a below average Net Basin Supply which would draw down lake levels a bit. Currently, Lakes Michigan-Huron are continually seeing higher than average precipitation so it is unlikely that water levels will go down as we roll in to 2020.
Where can I go for more information?
See our Coastal Hazards page for details about the impacts of high water levels, including erosion, flooding, and navigation issues.
Our blog post Resources for Great Lakes Coastal Property Owners: Where do I start? and Resilience Resources have links to many resources to help understand coastal hazards, weigh the risks coastal hazards pose to property, understand options for addressing these hazards, and get started on implementing actions if necessary. One featured resource includes Adapting to a Changing Coast: Options and Resources for Lake Michigan Property Owners (pictured right)
Great Lakes Water Budgets from the University of Michigan gives a bit more information into what makes the lakes go up and down