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Great Lakes Water Levels Current and Historical Data & Graphs (November 2021 Update)

Each month we summarize reports and data from the Army Corps of Engineers – Detroit District’s Monthly and Weekly reports for Great Lakes Water Levels and Great Lakes Water Level History. We present a single-page view of the changes in lakes levels from month to month are presented for Lakes Huron-Michigan, Lake Superior, Lake Erie, Lake Ontario, and Lake St. Clair.


Great Lakes Basin Weather Conditions Over the Past Month Affecting Water Levels

During the month of October, the Great Lakes basin experienced above-average precipitation. The Lake Superior basin got 78 percent of its typical precipitation, while Lake Michigan-Huron received near-average precipitation. The Erie and Ontario basins got 179 percent and 169 percent of average precipitation, respectively. Similarly, runoff in the Erie and Ontario basins, as well as the lower Michigan-Huron basin, was much above average.

Lake Superior’s water supply was below normal, while Lake Michigan-supply Huron’s was above average. Water levels on Lakes Erie and Ontario were significantly above average, with Erie’s preliminary water supplies ranking second-highest on record for the month of October. All lakes’ outflows remained above normal, with the exception of Lake Superior, which had a below-average outflow.

Except For Lake Superior, All The Great Lake Water Levels Remain Above Long Term Average

All of the lakes experienced a drop in lake level from September to October, with the exception of Lake Erie, which stayed at the same level. Lake Superior plummeted by one inch, Lake Michigan-Huron by around two inches, Lake St. Clair by one inch, and Lake Ontario by less than an inch. All of the lakes are expected to continue their seasonal drops through the autumn and into early winter, according to the 6-month projection.

Lakes Michigan-Huron Water Levels

Lakes Michigan-Huron Water Levels November 2021
Lakes Michigan-Huron Water Levels November 2021

On November 12th, the water level is forecasted at 580.02 feet. Lake Michigan-Huron had dropped 13 inches since November 2020 and dropped another 5 inches over the past month. Levels were down 23 inches below the monthly high mean record set in 1986. Lake Huron remains at 45 inches above the record monthly low, set in 1964. The lakes are expected to drop by two inches through mid-December 2021. Lake Michigan-Huron is expected to stay above its long-term monthly mean water level for the rest of 2021. For reporting purposes, Lakes Michigan-Huron is the same body of water.

Lake Superior Water Level

Lake Superior Water Level November 2021
Lake Superior Water Level November 2021

As of November 12th, 2021, the Lake Superior water level is forecasted to be 601.71 feet. This is 5 inches less than the levels reported last month. This is 19 inches less than the high record monthly mean water level set in 1985 and 15 inches higher than the lowest record set in 1925. Over the next month, Lake Superior is expected to drop by two inches. Lake Superior is expected to stay at or slightly below its long-term monthly mean water level for the rest of 2021.

Early projects show that due to La Nina weather patterns of the past, Lake Superior may again approach record water levels during the Fall of 2021.

Lake St. Clair Water Level

Lake St. Clair Water Levels November 2021
Lake St. Clair Water Levels November 2021

As of November 12th, 2021, Lake St. Clair’s water level is forecasted to be 575.85 feet. The lake dropped 2 inches in the past month. This is 12 inches less than the high record monthly mean water level set in 1986 and 53 inches higher than the lowest record set in 1934. Over the next month, Lake St. Clair is expected to drop by 4 inches through mid-December. Lake St. Clair is expected to stay above its long-term monthly mean water level for the rest of 2021.

Lake Erie Water Level

Lake Erie Water Levels November 2021
Lake Erie Water Levels November 2021

As of November 12th, 2021, Lake Erie’s water level is forecasted to be 573.10 feet. This is no change from the recorded lake level last month. This is 7 inches less than the record high water level set in 1986 and 58 inches higher than the lowest record set in 1934. Over the next month, Lake Erie is expected to drop by 4 inches. Lake Erie is expected to stay above its long-term monthly mean water level for the rest of 2021.

Lake Ontario Water Level

Lake Ontario Water Levels November 2021
Lake Ontario Water Levels November 2021

As of November 12th, Lake Ontario’s water level is forecasted to be 245.54 feet. This is an increase of 3 inches in the past month. This is 13 inches less than the record high monthly mean water level set in 1945 and 43 inches higher than the lowest record set in 1934. Over the next month, Lake Ontario is expected to drop by 2 inches. Lake Ontario is expected to be slightly above its long-term monthly mean water level for the rest of 2021.


November-December Downbound Outflows Below Average For Superior, Above Average For Rest of Great Lakes

According to forecasts, Lake Superior’s discharge through the St. Marys River will be lower than usual in November. According to forecasts, Lake Michigan-Huron outflow through St. Clair River and Lake St. Clair outflow into Detroit River will be higher than typical in November. Lake Erie’s outflow into the Niagara River is expected to be above average in November, while Lake Ontario’s outflow through the St. Lawrence River is expected to be above average.


Great Lakes Water Level Future Scenarios

These scenarios are intended to depict events that might occur under historical weather and water supply conditions, with scenarios chosen based on similarity to current conditions. Based on past hydrologic conditions and water supplies, this tool has mostly been used to depict the likely range of water levels in the future year.

Water levels follow a cyclical cycle, with lakes often declining during the autumn and early winter owing to increased evaporation as temperatures drop and cold air flows over the comparatively warm lake waters. Water levels often rise in the spring as a result of higher precipitation and increased runoff from melting. The combined impact of precipitation over the lake, evaporation from the lake, and runoff to the lake is referred to as Net Basin Supply (NBS).

A La Nia is expected to have an influence on the final few months of Great Lakes water levels in 2021 and the beginning of 2022. If a La Nia develops during the winter months, it will be the second winter in a row with La Nia conditions.

The graphs below features a purple plume representing 10 years where La Nia conditions occurred the previous winter and developed again the following year. Because a La Nia developed in the winter of 2020-21 and is predicted to form again in the winter of 2021-22, the years included in the plume would indicate the second year of La Nia conditions. Three years inside the plume have been chosen to demonstrate the variation in hydroclimate.


Lake Superior Lake Level Forecast Through 2022

Lake Superior Level Forecast Thru 2022
Lake Superior Mean Water Levels Thru 2022

Lake Superior’s water levels are expected to drop below their long-term average in 2022.


Lakes Michigan-Huron Forecast Through 2022

Lakes Michigan-Huron Mean Water Levels Thru 2022
Lakes Michigan-Huron Mean Water Levels Thru 2022

Lakes Michigan-Huron is expected to continue to be above its long-term average in 2022.


Lake St.Clair Forecast Through 2022

Lake St.Clair Mean Water Levels Thru 2022
Lake St.Clair Mean Water Levels Thru 2022

Lake St.Clair is expected to continue to be above its long-term average in 2022.


Lake Erie Forecast Through 2022

Lake Erie Mean Water Levels Thru 2022
Lake Erie Mean Water Levels Thru 2022

Lake Erie is expected to continue to be above its long-term average in 2022.


Water Level Data 1919-2021

Below are the monthly mean average water levels for each of the Great Lakes. All levels are referenced to the International Great Lakes Datum of 1985 (IGLD 85). Water levels have been coordinated with Canada for 1918-2020.

Great Lakes Water Levels 1919-2021
Great Lakes Water Levels 1919-2021

Dynamic Great Lakes – Lake Level Viewer – From NOAA


Key Questions on Great Lakes Water Levels

Are Great Lakes water levels climbing or receding?

All the Great Lake water levels remain above their long-term average. Except for Lake Superior, all the Great Lakes are expected to remain above their long-term averages for the next five years.

Why are Great Lakes water levels staying so high?

Water levels follow a seasonal cycle where water levels rise in the spring due to increased precipitation and enhanced runoff from snowmelt. In the fall, the lakes generally decline due to an increase in evaporation as temperatures decline and cold air moves over the relatively warm lake waters. However, the high rates of precipitation in the Upper Great Lakes have kept overall lake levels high


Great Lakes Water Levels Reading from Amazon

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