Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2016

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

1973

JUN

1952

JUL

1947

AUG

1947

SEP

1947

OCT

1945

NOV

1945

DEC

1945

2017

JAN

1946

1935

FEB

1952

1936

MAR

19521935

APR

19731935

MAY

19731935

JUN

19521935

JUL

19471934

AUG

19471934

SEP

19471934

OCT

19451934

NOV

19451934

DEC

19451934

2018

JAN

1946

1935

FEB

1952

1936

MAR

19521935

APR

19731935

MAY

19731935

JUN

19521935

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

2016

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2017

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

2018

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

2016

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2017

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

2018

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

602.76

183.72602.17183.54603.05

183.81

1985

600.13182.92

1925

601.71

183.40

MichHuron

580.02176.79

579.10

176.51

581.56177.26

1986

576.15

175.61

2012

578.51

176.33

St.

Clair

575.33

175.36

574.54175.12576.77

175.80

1986

571.65174.24

1964

573.85

174.91

Erie

572.18

174.40

571.42174.17573.79174.89

1986

568.21

173.19

1934

570.83173.99

Ontario

245.31

74.77

244.29

74.46

246.72

75.20

1945

241.93

73.74

1934

244.49

74.52

DECEMBER MEAN LAKE LEVELS

(IGLD 1985)

* 2017 Ft.

M.

2016 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional** Average, Maximum and Minimum for period 1918-2016

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).
 Information 

Recorded 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 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) 226-6442 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 2017

According to preliminary estimates, basin-wide precipitation was below average for most of the Great Lakes, with 

the exception of Lake Superior. Lake Superior received slightly above average precipitation with estimates at 105% 

of its average December precipitation. The rest of the basins received less than 65% of their average December 

precipitation, with Michigan-Huron and Ontario receiving 63% and 62% respectively, and Lake Erie trailing with 49% 

of its December precipitation. On the whole, the Great Lakes basin received 70% of average December precipitation. 

Over the last 12 months, the total precipitation has been just above average for the Great Lakes basin. Net basin 

supply was below average for all but Lake Superior. Lake outflows in December were above average for all lakes. 

All of the lakes were above their December long-term average water levels. From November to December, all of the 

lakes’ levels declined, where Lake Superior, Lake Michigan-Huron and Lake Erie fell 2 inches, Lake St. Clair fell 3 

inches and Lake Ontario fell by 4 inches. This December’s levels were 9 to 12 inches above last year’s levels for all 

but Lake Superior, which was 7 inches above last year’s December level. All of the lakes are below their record high 

levels. Lake Superior is 4 inches below its record December high level, while other lakes are 17 to 19 inches below. 

 

PRELIMINARY PRECIPITATION (INCHES) 

BASIN 

December 12-Month Comparison 

2017 Average Diff. % of 

Average 

Last 12 

months 

Average Diff. % of 

(1900-2014) (1900-2014) Average 

Superior 2.13 2.02 0.11 105 34.00 30.52 3.48 111 

Michigan-Huron 1.49 2.35 -0.86 63 35.05 32.57 2.48 108 

Erie 1.32 2.68 -1.36 49 36.57 35.65 0.92 103 

Ontario 1.85 2.97 1.80 62 41.35 35.87 5.48 115 

Great Lakes 1.67 2.37 -0.70 70 35.75 32.76 2.99 109 

 

 LAKE December Net Basin Supplies1 (cfs) December Outflows2 (cfs) 

2017 Average 

(1900-2008) 2017 Average3(1900-2008)

Superior 61,000 -22,000 89,000 72,000 

Michigan-Huron -17,000 34,000 210,000 183,000 

Erie 0 21,000 242,000 201,000 

Ontario 18,000 27,000 286,000 234,000 

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