January 8, 2020
By Lydia Salus, Coastal Engineering Outreach Specialist, Wisconsin Sea Grant
The water levels on all the Great Lakes still remain above average as of the beginning of the New Year. Lake Michigan is currently above the highest monthly average for the month of January that was set for the Lake in 1987. If the lake remains at this level, it would be the first new monthly record set for Lake Michigan in our recent period of high water levels. While Lake Michigan saw notable precipitation at the end of 2019, precipitation in the Great Lakes Basin was close to average for December.
Here are five things to know about water levels on Lake Michigan for January 2020.
What are the current water levels on Lake Michigan?
The water level of Lake Michigan as of January 3, 2020 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||1 inch lower|
|One year ago||16 inches higher|
|Average January (from 1918 to 2018)
||37 inches higher|
|Record January monthly mean (set in 1987)||2 inches higher|
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 January 2020 below). With water levels on Lake Michigan within an inch of the December monthly record high set in 1986, the forecast indicates a high likelihood of record or near-record water levels throughout the beginning of 2020.
Water levels are in the midst of a slight seasonal decline, with a projected drop of an additional inch by February 3rd, 2020. This decrease in water levels generally occurs 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. However, this winter has seen a rather small seasonal decline of only 5 inches so far from last year’s peak in July. Water levels would be expected to begin a seasonal rise again around March when runoff and precipitation increase.
Why are lake levels still 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, causing a rise in lake levels. Over the last five years, Net Basin Supply has been consistently positive, driving all the Great Lakes to rise.
In our blog “It’s Evaporation Season (Normally)”, we discussed how in 2019 Lake Michigan experienced above average evaporation in August, October, and November and below average evaporation in September. However, heavy precipitation throughout the summer and fall outweighed the evaporation which led to a positive Net Basin Supply meaning that more water entered the Lake than left the Lake and water levels remained high through the end of 2019.
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. This fall, Lakes Michigan-Huron continued to see higher than average precipitation so it is unlikely that water levels will go down as we roll in to 2020.
Five places you can find more information:
- 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? has links to many resources to help
- understand coastal hazards
- weigh the risks coastal hazards pose to property
- understand options for addressing these hazards
- get started on implementing actions if necessary.
- The Great Lakes Water Budgets from the University of Michigan gives more information about what makes the lakes go up and down
- The US Army Corps’ Great Lakes Information page has tons of details on water levels.
- Our Resource of the Month featured here.