February 17, 2020
By Lydia Salus, Coastal Resilience Project Assistant, Wisconsin Sea Grant
The water levels on all the Great Lakes still remain above their long-term averages as of the beginning of February 2020. Lake Michigan surpassed its record-high monthly mean for January dating back to 1918. This is the first new monthly record set for Lake Michigan in our recent period of high water levels. The Great Lakes Basin experienced more precipitation as rain instead of snow throughout January and preliminary results suggest that evaporation on Lake Michigan was below average.
Here are five things to know about water levels on Lake Michigan for February 2020.
What are the current water levels on Lake Michigan?
The water level of Lake Michigan as of February 14, 2020 is at an elevation of 581.59 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 USACE’s Weekly Water Level Update and USACE’s Water Level Summary).
|Compared to…||Current Water Levels are…|
|One month ago||less than 1 inch higher|
|One year ago||19 inches higher|
|Long-term February monthly average (from 1918 to 2019)
||39 inches higher|
|Record February monthly mean (set in 1986)||6 inches higher|
What is the outlook for future water levels?
The US Army Corps of Engineers (USACE) projects higher than average and potentially record high water levels to persist for at least the next six months (see six-month forecast issued for February 2020 below). In their Monthly Bulletin of Water Levels, the USACE reminds coastal communities that flood prone areas are expected to remain vulnerable.
While water levels on Lake Michigan would normally be in the midst of a seasonal decline this time of year, the USACE is projecting that water levels will actually increase by an inch by March 14, 2020. A 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, the water levels are expected to continue to rise through March when Lake Michigan generally begins its seasonal rise.
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.
Due to above average temperatures in January across the Great Lakes Basin, more precipitation fell as rain instead of snow contributing to runoff. The runoff from precipitation, in addition to snowmelt, led to above normal runoff to Lake Michigan. Typically, precipitation would fall as snow this time of year and would remain stored in snowpack. Additionally, preliminary data suggests that evaporation was below normal for Lake Michigan (see modeled evaporation below). Above normal runoff coupled with below average evaporation in January caused the lake levels to reach a record high monthly mean for January.
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 USACE’s Detroit district “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. This winter, Lake Michigan continued to see higher than average precipitation and below average evaporation, so it is unlikely that water levels will go down in the early months of the new year.
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.
- Ice information can be found at the National Ice Center’s website.