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Historical Lake Levels- Lake Michigan-Huron

This page is part of the project: Great Lakes Climate Change and Lake-Levels

Lake Michigan-Huron

Note: Hydrologically Lake Michigan and Lake Huron are a single lake.


Lake Water Levels: Historical Monthly Data

Data Source: Glerl (NOAA)
Points of Interest: The Chicago Diversion was completed in 1900 that changed the flow of the Chicago River from Lake Michigan into the Mississippi River.

Info on monthly data: The data comes from the Great Lakes Environmental Research Lab (GLERL) and spans from January 1860 until September 2016. The data from 1860-1917 comes from a master gauge that was present on each lake. These gauges might not represent the true lake-wide average level if they were far from the lake's outlet due to isostatic rebound. From 1918-2016, there were more gauges present on the lakes (at present 53 monitoring stations in the US and 33 stations in Canada) which gives a more accurate representation of the lake's water levels. For more information on the gauges visit:

The data set used to make these figures was a combination of the master gauge data from each lake (the 1860-1917 data) and the 1918-2016 water level data that comes from GLERL. These data sets were processed using Python code created by GLISA which created a certain output, in this case a csv file (access below).

Great Lakes water levels are measured from an elevation reference point referred to as the International Great Lakes Datum of 1985 (IGLD 85). This datum is referenced to sea level as measured at Rimouski, Quebec, near the mouth of the St. Lawrence River. Every 25-30 years, the IGLD is changed to account for crustal movement–the ‘bouncing back’ of the earth’s crust from the weight of the glaciers. This datum is the average water level line in the graph.


Data Access: /media/u3841/files/Monthly_lake_levels_miHuron.csv

Lake Water Levels: Decadal Averages


Decade Water Levels (m) Standard Deviation
1861-1870 177.02 0.24
1871-1880 177.01 0.21
1881-1891 177.11 0.23
1891-1900 176.54 0.16
1901-1910 176.66 0.17
1911-1920 176.59 0.21
1921-1930 176.32 0.34
1931-1940 175.99 0.19
1941-1950 176.44 0.23
1951-1960 176.56 0.38
1961-1970 176.24 0.34
1971-1980 176.85 0.23
1981-1990 176.77 0.32
1991-2000 176.53 0.31
2001-2010 176.06 0.17
2011-2016 176.25 0.35
Data Source: Glerl (NOAA)


A box and whisker graph showing average lake levels on decadal (10 year) time scales. For example the box on 1861 is the average from 1861 to 1870, the box on 1871 is the average from 1871 to 1880, and so on. The red line in the box is the median for that decadal average, the top and bottom of the box are the 75th and 25th percentiles, the dashed lines are the extreme data points not considered outliers, and the red '+' signs are the outliers.

Lake Water Levels: 30 Year Averages

30 Year Period Water Levels (m) Standard Deviation
1861-1890 177.05 0.23
1871-1900 176.89 0.32
1881-1910 177.78 0.31
1891-1920 176.60 0.19
1901-1930 176.52 0.29
1911-1940 176.30 0.35
1921-1950 176.25 0.32
1931-1960 176.33 0.37
1941-1970 176.41 0.35
1951-1980 176.55 0.41
1961-1990 176.62 0.40
1971-2000 176.71 0.32
1981-2010 176.45 0.40
Data Source: Glerl (NOAA)

A box and whisker graph showing average lake levels on 30 year time scales. For example the box on 1861 is the average from 1861 to 1890, the box on 1871 is the average from 1871 to 1900, and so on. The red line in the box is the median for that 30 year average, the top and bottom of the box are the 75th and 25th percentiles, the dashed lines are the extreme data points not considered outliers, and the red '+' signs are the outliers.


Annual Water Level Cycle


Data Source: Glerl (NOAA)
Note: The average was done using monthly data from 1860 to 2016.
The high water level period for Lake Michigan-Huron is mid-summer (June-Aug range) and the low water level period is late winter into early spring (Jan-Mar range) which can be seen in the graph above. There can be year-to-year variations but these time ranges are the average time period that the lake experiences its annual high or low water mark.

Data Source: Glerl (NOAA)


When comparing the annual cycle of the lake level from the present decade going back to the 1860s, there hasn't been a significant change in the time during the year that the low and high water marks occur. The lows in each 30 year period all still occurred in Feburary and the highs occurred in July with the exception of the most recent 30 year period which had the high occur in June. This could mean that if the timing of the high/low in the annual cycle is changing, it hasn't changed by a large time range to be seen. That is, the data is monthly so if the timing of the high/low has changed by a week or two, it would be hard to see as it could still occur in the same month of the year just a different week in that month.
Sustained Periods of High/Low Water Levels