Ft.

-1

0

+ 1

+ 2

+ 3

+ 4

+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9

+ 1.2

+ 1.5

2020

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

2017

JUN

2019

JUL

2019

AUG

1947

SEP

1947

OCT

1945

NOV

1945

DEC

1945

2021

JAN

1946

1935

FEB

1952

1936

MAR

1952

1935

APR

1973

1935

MAY

2017

1935

JUN

2019

1935

JUL

2019

1934

AUG

1947

1934

SEP

1947

1934

OCT

1945

1934

NOV

1945

1934

DEC

1945

1934

2022

JAN

1946

1935

FEB

1952

1936

MAR

1952

1935

APR

1973

1935

MAY

2017

1935

JUN

2019

1935

LAKE ONTARIO

CHART DATUM 243.3 FEET (74.2 METERS)

Ft.

-1

0

+ 1

+ 2

+ 3

+ 4

+ 5

+ 6

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9

+ 1.2

+ 1.5

+ 1.8

2020

JAN

1987

FEB

2020

MAR

2020

APR

2020

MAY

2020

JUN

2019

JUL

2019

AUG

2019

SEP

2019

OCT

1986

NOV

1986

DEC

1986

2021

JAN

1987

1935

FEB

2020

1936

MAR

2020

1934

APR

2020

1934

MAY

2020

1934

JUN

2019

1934

JUL

2019

1934

AUG

2019

1934

SEP

2019

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1934

2022

JAN

1987

1935

FEB

2020

1936

MAR

2020

1934

APR

2020

1934

MAY

2020

1934

JUN

2019

1934

LAKE ERIE

CHART DATUM 569.2 FEET (173.5 METERS)

Ft.

-1

0

+ 1

+ 2

+ 3

+ 4

+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9

+ 1.2

+ 1.5

2020

JAN

2020

FEB

1986

MAR

2020

APR

2020

MAY

2020

JUN

2020

JUL

2019

AUG

2020

SEP

2020

OCT

1986

NOV

1986

DEC

1986

2021

JAN

2020

1936

FEB

1986

1926

MAR

2020

1934

APR

2020

1926

MAY

2020

1934

JUN

2020

1934

JUL

2019

1934

AUG

2020

1934

SEP

2020

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1964

2022

JAN

2020

1936

FEB

1986

1926

MAR

2020

1934

APR

2020

1926

MAY

2020

1934

JUN

2020

1934

LAKE ST. CLAIR

CHART DATUM 572.3 FEET (174.4 METERS)

Ft.

-1

0

+ 1

+ 2

+ 3

+ 4

+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9

+ 1.2

+ 1.5

2020

JAN

2020

FEB

2020

MAR

2020

APR

2020

MAY

2020

JUN

2020

JUL

2020

AUG

2020

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2021

JAN

2020

2013

FEB

2020

1964

MAR

2020

1964

APR

2020

1964

MAY

2020

1964

JUN

2020

1964

JUL

2020

1964

AUG

2020

1964

SEP

1986

1964

OCT

1986

1964

NOV

1986

1964

DEC

1986

2012

2022

JAN

2020

2013

FEB

2020

1964

MAR

2020

1964

APR

2020

1964

MAY

2020

1964

JUN

2020

1964

LAKES MICHIGAN-HURON

CHART DATUM 577.5 FEET (176.0 METERS)

Ft.

-1

0

+ 1

+ 2

M.

-0.3

0

+ 0.3

+ 0.6

2020

JAN

2020

FEB

2020

MAR

1986

APR

1986

MAY

2019

JUN

2019

JUL

2019

AUG

2019

SEP

2019

OCT

1985

NOV

1985

DEC

1985

2021

JAN

2020

1926

FEB

2020

1926

MAR

1986

1926

APR

1986

1926

MAY

2019

1926

JUN

2019

1926

JUL

2019

1926

AUG

2019

2007

SEP

2019

2007

OCT

1985

1925

NOV

1985

1925

DEC

1985

1925

2022

JAN

2020

1926

FEB

2020

1926

MAR

1986

1926

APR

1986

1926

MAY

2019

1926

JUN

2019

LAKE SUPERIOR 1926

CHART DATUM 601.1 FEET (183.2 METERS)

ELEVATIONS REFERENCED TO THE CHART DATUM OF EACH RESPECTIVE LAKE

Superior

601.41

183.31

602.46

183.63

603.05

183.81

1985

600.13

182.92

1925

601.74

183.41

MichHuron

579.69

176.69

581.17

177.14

581.56

177.26

1986

576.15

175.61

2012

578.61

176.36

St.

Clair

575.52

175.42

576.21

175.63

576.77

175.80

1986

571.65

174.24

1964

573.92

174.93

Erie

572.77

174.58

573.00

174.65

573.79

174.89

1986

568.21

173.19

1934

570.90

174.01

Ontario

245.64

74.87

244.82

74.62

246.72

75.20

1945

241.93

73.74

1934

244.52

74.53

DECEMBER MEAN LAKE LEVELS

(IGLD 1985)

* 2021 Ft.

M.

2020 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional

** Average, Maximum and Minimum for period 1918-2020

LEGEND

LAKE LEVELS

RECORDED

PROJECTED

AVERAGE **

MAXIMUM **

1985

1985

1973 1973

MINIMUM **

1936

1934

1926 1934

JANUARY 2022

US Army Corps

of Engineers

Detroit District

MONTHLY BULLETIN OF

LAKE LEVELS FOR THE

GREAT LAKES

Monthly mean water levels for the previous year and the

current year to date are shown as a solid line 

on the hydrographs. A projection for the next

six months is given as a dashed line. This 

projection is based on the present condition 

of the lake basin and anticipated future 

weather. The shaded area shows a range of

possible levels over the next six months 

dependent upon weather variations. Current

and projected levels (solid and dashed lines) 

can be compared with the 1918-2020 average

levels (dotted line) and extreme levels 

(shown as bars with their year of occurrence).

The legend below further identifies the 

information on the hydrographs. 

The levels on the hydrographs are shown in

both feet and meters above (+) or below (-) 

Chart Datum. Chart Datum, also known as 

Low Water Datum, is a reference plane on 

each lake to which water depth and Federal 

navigation improvement depths on navigation 

charts are referred.

All elevations and plots are referenced to the

International Great Lakes Datum 1985 (IGLD 1985). 

IGLD 1985 has its zero base at Rimouski, Quebec 

near the mouth of the St. Lawrence River 

(approximate sea level). 

Visit our website for more information:

https://www.lre.usace.army.mil/greatlakes
Information

Recorded monthly mean water levels in this bulletin are derived from a representative network of water level gages 

on each lake (see cover map). Providers of these data are the U.S. Department of Commerce, NOAA, National 

Ocean Service, and Integrated Science Data Management, Department of Fisheries and Oceans, Canada. The 

Detroit District, Corps of Engineers and Environment and Climate Change Canada derive historic and projected lake 

levels under the auspices of the Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data.

This bulletin is produced monthly as a public service. The Corps also, on a weekly basis publishes online the Great 

Lakes, Connecting Channels and St. Lawrence River Water Levels and Depths, which provides a forecast of depths 

in the connecting rivers between the Great Lakes and the International Section of the St. Lawrence River. This 

Monthly Bulletin of the Lake Levels for the Great Lakes is available free of charge by writing to the address shown 

on the front cover, by calling (313) 226-6441 or emailing hhpm@usace.army.mil. Notices of change of address 

should include the name of the publication. This information is available on the internet at 

https://www.lre.usace.army.mil/Missions/GreatLakesInformation.aspx.

Great Lakes Basin Hydrology

December 2021

Preliminary estimates of precipitation indicate the Great Lakes basin received near average precipitation during the 

month of December. Lakes Superior received 125% of its December average precipitation while Lakes MichiganHuron and Ontario received below average precipitation. Lake Erie received near average precipitation in December. 

Water supplies were well above average on all lakes likely reflecting the average precipitation received by the entire 

basin and above average runoff. Outflows from Lakes Michigan-Huron, Erie, and Ontario were above average, while

Lake Superior’s outflow was below average.

From November to December, all the lakes experienced a decline in lake level, except for Lake Ontario which 

remained near its November level. Lakes Superior and Michigan-Huron each declined about 3 inches and Lakes St. 

Clair and Erie declined 2 inches. The Great Lakes 6-month forecast projects Lakes Superior, Michigan-Huron, and 

St. Clair will decline from December to January while Lake Erie remains near its December water level into January. 

The 6-month forecast indicates Lake Ontario will rise slightly from December to January.

PRECIPITATION (INCHES)

BASIN

December 12-Month Comparison

2021 Average Diff. % of 

Average

Last 12 

months 

Average Diff. % of 

(1900-2018) (1900-2018) Average

Superior 2.51 2.01 0.50 125 24.44 30.59 -6.15 80

Michigan-Huron 2.11 2.40 -0.29 88 28.36 32.87 -4.51 86

Erie 2.78 2.68 0.10 104 34.74 35.91 -1.17 97

Ontario 2.43 2.99 -0.56 81 34.32 36.34 -2.02 94

Great Lakes 2.33 2.40 -0.07 97 28.78 32.99 -4.21 87

Lake

December WATER SUPPLIES1 (cfs) December OUTFLOW2 (cfs)

2021 Average3

(1900-2008) 2021 Average3(1900-2008)

Superior 34,000 -20,000 60,000 72,000

Michigan-Huron 76,000 35,000 210,000 183,000

Erie 46,000 22,000 249,000 201,000

Ontario 50,000 28,000 301,000 234,000

Notes: Values (excluding averages) are based on preliminary computations; cfs denotes cubic feet per second.

1 Net basin supply is the net result of precipitation falling on the lake, runoff from precipitation falling on the land which flows to 

the lake, and evaporation from the lake. Negative net basin supply denotes evaporation exceeded runoff and precipitation. 

The net total supply can be found by adding the net basin supply and the outflow from the upstream lake.

2 Does not include diversions.

3 Lake Ontario average water supplies and average outflows are based on period of record 1900-2005