Through the spring months (March, April, May), Lake Michigan water levels began their seasonal rise. Water levels are expected to continue rising through July. Above average precipitation this spring increased water supply to Lake Michigan. Over the next 6-months the USACE predicts that Lake Michigan water levels will be 1 – 2 inches above the long-term average.

Water Levels on Lake Michigan-Huron

Here are five things to know about water levels on Lake Michigan for Early Summer 2024.

What are the current water levels on Lake Michigan?

The water level of Lake Michigan as of June 7, 2024, was at an elevation of 579.56 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 present (statistics from USACE’s Weekly Water Level Update and USACE’s Water Level Summary).

What is the outlook for future water levels?

Lake Michigan water levels declined over the course of winter before beginning their seasonal rise in March. The USACE projects that water levels will continue to rise one more inch by the end of June. The USACE 6-month forecast of Great Lakes Water levels shows an expected summer peak in July followed by the regular decline in late summer and fall, with water levels continuing to be 1-2 inches above the long-term average. The image below shows the water level forecast issued for June 2024, with projected water levels in green, past water levels in red, and long-term average water levels in blue.

USACE six-month water level forecast for Lake Michigan-Huron retrieved for June 2024 from: https://www.lre.usace.army.mil/Missions/Great-Lakes-Information/Great-Lakes-Water-Levels/Water-Level-Forecast/

What are current and predicted climate conditions like?

On June 13, NOAA’s Climate Prediction Center announced the end of last year’s El Niño cycle, with a transition to ENSO-neutral conditions. La Niña conditions are favored to develop in July-September 2024 and persist through the Northern Hemisphere winter of 2024-2025. Climate forecasts for June predict above-normal temperatures in Wisconsin. After a wetter than average May, precipitation forecasts show equal chances for a wet, dry, or near-average June (see precipitation outlook map from NOAA Climate.gov below). Check out the NOAA Climate Prediction Center’s U.S. climate outlook for June 2024 for more.

The U.S. precipitation outlook for June 2024. Map by NOAA Climate.gov, based on data from the Climate Prediction Center. From: https://www.climate.gov/news-features/understanding-climate/us-climate-outlook-june-2024

What is behind Great Lakes water level fluctuations?

The story of Great Lakes water level changes is told by Net Basin Supply. Net Basin Supply (NBS) accounts for the 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.

NBS represents the net influence of precipitation over the lake, runoff from a lake’s watershed into the lake, and evaporation from the lake’s surface. Image credit: National Oceanic and Atmospheric Administration

In general, when Net Basin Supply is positive, more water enters the lake than leaves, causing a rise in lake levels. When Net Basin Supply is negative, more water leaves the lake than enters, causing a drop in lake levels. (Click here for more detail).

The annual peak Net Basin Supply occurs when runoff peaks in the spring and experiences its minimum when over-lake evaporation peaks in the winter. These maximums and minimums in Net Basin Supply correspond to the seasonal water level rise and fall. (Click here for more detail).

Evaporation takes place when the Lake’s surface water temperature is warmer than the air temperature. Though Lake Michigan had low ice cover this year which left the water surface open to evaporation, evaporation was well below average in December (see USACE graphic on monthly evaporation rates below) and only slightly above average in January and February. This is due to a relatively small difference between the air temperatures and lake surface temperatures in recent months.

Evaporation relative to long term average Evaporation for the past 5 years. Retrieved from: https://www.lre.usace.army.mil/Missions/Great-Lakes-Information/Great-Lakes-Information-2/Basin-Conditions/

What is making water levels go down?

Since monthly record highs in 2020, the Great Lakes water levels have been trending downwards. This trend has continued and water levels are lower than they were at the same time in 2023. However, water levels still remain above the long term average. The graph below visualizes the monthly difference from the long-term average NBS for the past five years. Red bars represent below average NBS, whereas blue bars represent above average NBS.

Water level fluctuation is a process that occurs annually due to changes in net basin supply. Water supplies fluctuated throughout the winter and spring, with no months extremely out of balance. This has led to a seasonal winter water level decline followed by a spring increase that has been relatively consistent with the long-term average trend.

NBS relative to long term average NBS for the past 5 years. Retrieved from: https://www.lre.usace.army.mil/Missions/Great-Lakes-Information/Great-Lakes-Information-2/Basin-Conditions/

Places you can find more relevant information:

1. In this Adapting to A Changing Coast PBS Special, Dr. Adam Bechle explains how fluctuations in rainfall, runoff, and evaporation cause the Great Lakes’ water levels and coastlines to vary.
2. NOAA’s Climate.gov site hosts climate data and information to help you understand climate processes and make decisions on how to manage climate-related risks and opportunities.
   • U.S. Climate outlook for June 2024
   • El Niño and La Niña
   • Great Lakes Chapter of the Climate Resilience Toolkit
3. Our Coastal Hazards page for details about the impacts of high water levels, including erosion, flooding, and navigation issues.
4. Our Policy, Planning, and Risk Reduction Strategies page has tools and resources to help local governments identify local resilience opportunities.