Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2018

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

2017

JUN

2017

JUL

2017

AUG

1947

SEP

1947

OCT

1945

NOV

1945

DEC

1945

2019

JAN

1946

1935

FEB

1952

1936

MAR

19521935

APR

19731935

MAY

20171935

JUN

20171935

JUL

20171934

AUG

19471934

SEP

19471934

OCT

19451934

NOV

19451934

DEC

19451934

2020

JAN

1946

1935

FEB

1952

1936

MAR

19521935

APR

19731935

MAY

20171935

JUN

20171935

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

2018

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2019

JAN

19871935

FEB

1987

1936

MAR

1986

1934

APR

19851934

MAY

1986

1934

JUN

1986

1934

JUL

1986

1934

AUG

1986

1934

SEP

1986

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1934

2020

JAN

19871935

FEB

1987

1936

MAR

1986

1934

APR

19851934

MAY

1986

1934

JUN

1986

1934

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

2018

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2019

JAN

19861936

FEB

19861926

MAR

1986

1934

APR

19861926

MAY

1986

1934

JUN

1986

1934

JUL

1986

1934

AUG

1986

1934

SEP

1986

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1964

2020

JAN

19861936

FEB

19861926

MAR

1986

1934

APR

19861926

MAY

1986

1934

JUN

1986

1934

CHART DATUM 572.3 FEET (174.4 METERS)

ELEVATIONS REFERENCED TO THE CHART DATUM OF EACH 

Superior

602.82183.74602.59183.67603.05

183.81

1985

600.13182.92

1925

601.74

183.41

MichHuron

581.53177.25580.15176.83

581.56177.26

1986

576.15

175.61

2012

578.54176.34

St.

Clair

576.38175.68575.69175.47576.77

175.80

1986

571.65174.24

1964

573.88174.92

Erie

573.10

174.68572.83

174.60

573.79174.89

1986

568.21

173.19

1934

570.87

174.00

Ontario

246.06

75.00

245.11

74.71

246.72

75.20

1945

241.93

73.74

1934

244.52

74.53

DECEMBER MEAN LAKE LEVELS

(IGLD 1985)

* 2019 Ft.

M.

2018 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional** Average, Maximum and Minimum for period 1918-2018

1985

1985

1973 1973

1936

1934

1926 1934

LAKE ONTARIO

LAKE ERIE

LAKE ST. CLAIR

LEGEND

LAKE LEVELS

RECORDEDPROJECTEDAVERAGE **MAXIMUM **MINIMUM **

The levels on the hydrographs are shown inboth 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 shown in this bulletin are referenced to 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).

Provisional record high water levels reached in 2019 will be coordinated and reflected on the Monthly Bulletin in early 2020.
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 may be obtained 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 

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

Great Lakes Basin Hydrology

December 2019

Preliminary estimates indicate that precipitation was average across all of the Great Lakes in December, at 103% of 

average. Lake Superior basin observed precipitation that was 116% of average, where the snowfall in the last week 

contributed to a majority of the month’s precipitation. December temperatures were above normal across all of the 

Great Lakes, which contributed to enhanced runoff in the Lake Superior and Lake Michigan-Huron basins. 

Preliminary water supplies estimates were near record highs, ranking 5th highest on Lake Superior and 4th highest 

on record on Lake Michigan-Huron. Ontario observed above normal water supplies, approximately double its 

average for December, while Erie observed considerably below average water supplies. Outflows for all of the 

connecting channels were above average. 

Monthly mean water levels for December continued to be below their monthly record highs. Lake Superior, MichiganHuron, St. Clair, and Ontario continued their seasonal declines into December, by approximately 3, 0.5, 1 and 2

inches. Lake Erie maintained its monthly average level from November to December. Lake Michigan-Huron was 

within an inch of its monthly record December high from 1986. Over the next month, seasonal declines are 

forecasted on all the Great Lakes, except for Lake St. Clair and Lake Ontario, which are forecasted to rise by about 

a third of an inch and an inch, respectively.

PRECIPITATION (INCHES)

BASIN

December 12-Month Comparison

2019

Average

Diff. % of 

Average

Last 12 

months 

Average

Diff. % of 

(1900-2017) (1900-2017) Average

Superior 2.37 2.05 0.32 116 30.60 30.58 0.02 100

Michigan-Huron 2.32 2.35 -0.03 99 34.98 32.52 2.46 108

Erie 2.56 2.67 -0.11 96 36.88 35.53 1.35 104

Ontario 3.00 2.96 1.80 101 37.26 35.84 1.42 104

Great Lakes 2.44 2.38 0.06 103 34.16 32.74 1.42 104

 LAKE

December WATER SUPPLIES1(cfs) December OUTFLOW2

(cfs)

2019

Average

(1900-2008) 2019

Average3

(1900-2008)

Superior 39,000 -22,000 89,000 72,000

Michigan-Huron 165,000 34,000 251,000 183,000

Erie -8,000 21,000 254,000 201,000

Ontario 56,000 27,000 311,000 234,000

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