By Brian Allnutt, Planet Detroit
This article was republished with permission from Planet Detroit. Sign up for Planet Detroit’s weekly newsletter here.
Water levels on the Great Lakes and Lake St. Clair continued to decline below long-term averages over the winter, just a few years after lakes hit record highs in 2019 and 2020.
Lake levels are expected to begin their seasonal rise and stay close to long-term averages, according to the U.S. Army Corps of Engineers’ six-month forecast issued March 4.
The recent decline in Great Lakes water levels hasn’t been especially steep, but the overall trajectory of lake levels is one of increasing variability, according to Yi Hong, a research scientist at the Cooperative Institute for Great Lakes Research.
Lake Michigan and Lake Huron, which are technically two lobes of a single lake, saw record highs in 2020 less than a decade after being hit by record lows in 2012 and 2013, Corps records show.
Climate change-driven extreme storms and heatwaves are influencing lake level variability, but there isn’t enough data to show if levels will trend lower or higher over the long-term, Hong said.
Over the next six months, the Corps predicts water levels will stay below long-term averages on all the lakes, except possibly Lake Ontario.
Lake Michigan and Lake Huron will be the farthest below average. From March to August, levels will be 4 to 7 inches below last year’s levels and 11 to 12 inches below the long-term average. Closer to Detroit, Lake St. Clair will see water levels 6 to 10 inches below last year and 5 to 7 inches below the long-term average.
Megan Royal, a Corps hydraulic engineer, said the agency doesn’t anticipate any water level issues in the shipping channels and harbors used by Great Lakes freighters. Sediment can occasionally move into navigation channels and harbors, requiring emergency dredging, she said.
In an interview with Maritime Reporter TV, Eric Peace, vice president of the Lake Carriers Association, said Great Lakes shipping is negatively impacted by several factors, including severe weather over the fall and early ice cover. Dredging will continue to be a challenge for the industry, he said.
Dry falls, hot summers contribute to lake level declines
A pattern of dry fall seasons from 2023-2025 contributed to the Great Lakes’ falling water levels, Royal told Planet Detroit.
Last summer’s heat also led to near record-high lake temperatures, producing significant evaporation when the winter’s extremely cold air passed over relatively warm water, she said.
“Evaporation is very difficult to measure because of just how large the lakes are,” Royal said, adding that modeling showed evaporation from all the lakes except Lake Erie was above average from October to January.
The rate of decline in lake levels is beginning to stabilize as a drought eases in parts of the Great Lakes Basin and snowmelt drives runoff into the lakes, she said.
The National Weather Service’s Climate Prediction Center forecasts above normal precipitation across nearly all the U.S. portion of the Great Lakes Basin over the next three months. Temperatures in these areas mostly have equal chances of being above or below normal over the same time period.
