Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2017

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

2017

JUN

2017

JUL

2017

AUG

1947

SEP

1947

OCT

1945

NOV

1945

DEC

1945

2018

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

2019

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

2017

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2018

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

2019

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

2017

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2018

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

2019

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

602.59183.67

602.76

183.72603.05

183.81

1985

600.13182.92

1925

601.71

183.40

MichHuron

580.15176.83580.02176.79

581.56177.26

1986

576.15

175.61

2012

578.51

176.33

St.

Clair

575.69175.47575.33

175.36

576.77

175.80

1986

571.65174.24

1964

573.85

174.91

Erie

572.80

174.59

572.31

174.44573.79174.89

1986

568.21

173.19

1934

570.83173.99

Ontario

245.14

74.72

245.31

74.77

246.72

75.20

1945

241.93

73.74

1934

244.49

74.52

DECEMBER MEAN LAKE LEVELS

(IGLD 1985)

* 2018 Ft.

M.

2017 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional** Average, Maximum and Minimum for period 1918-2017

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 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 2018

Preliminary estimates indicate that the Great Lakes basin as a whole received below average precipitation in the 

month of December after a slightly below average November. Lakes Superior, Michigan-Huron and Erie were below 

average at 64%, 83% and 91% of their respective December averages. Lake Ontario received near average 

precipitation at 102% of a normal December amount. Water supplies for Lake Superior, Michigan-Huron and Ontario 

were all well above average, seemingly in contradiction to the precipitation values. A warmer than normal December 

can lead to increased runoff due to precipitation falling as rain, versus snow. Higher than average outflows persisted 

from November to December for each of the Great Lakes. 

Mean water levels for the month of December remained above their long-term average for all lakes. Lake Superior 

fell over the past month by approximately four inches. Levels on Michigan-Huron and St. Clair decreased by roughly 

an inch from November to December. On the contrary, Lake Erie and Ontario both increased from November to 

December, which is a season where the lakes typically decrease. The delayed decrease can be attributed to warmer 

temperatures and associated higher runoff. Relative to the December levels in 2017, Lake Superior and Ontario 

were about 2 inches below what they were, while Michigan-Huron, St. Clair and Erie were 2, 4 and 6 inches above. 

 

PRELIMINARY PRECIPITATION (INCHES) 

BASIN 

December 12-Month Comparison 

2018 Average Diff. % of 

Average 

Average Last 

12 Months 

Average Diff. % of 

(1900-2016) (1900-2016) Average 

Superior 1.31 2.04 -0.73 64 26.90 30.58 -3.68 88 

Michigan-Huron 1.97 2.36 -0.39 83 31.08 32.55 -1.47 95 

Erie 2.43 2.68 -0.25 91 36.19 35.62 0.57 102 

Ontario 3.02 2.97 1.80 102 35.43 35.87 -0.44 99 

Great Lakes 1.99 2.39 -0.40 83 31.03 32.77 -1.74 95 

 

 LAKE 

December WATER SUPPLIES1 (cfs) December OUTFLOW2 (cfs) 

2018 Average 

(1900-2008) 2018 Average3(1900-2008)

Superior -2,000 -22,000 81,000 72,000 

Michigan-Huron 105,000 34,000 214,000 183,000 

Erie 21,000 21,000 245,000 201,000 

Ontario 69,000 27,000 292,000 234,000 

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