Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2016

OCT

1945

NOV

1945

DEC

1945

2017

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

2017

JUN

2017

JUL

2017

AUG

1947

SEP

1947

OCT

19451934

NOV

19451934

DEC

19451934

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

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

OCT

1986

NOV

1986

DEC

1986

2017

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

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

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

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

OCT

1986

NOV

1986

DEC

1986

2017

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

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

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

CHART DATUM 572.3 FEET (174.4 METERS)

ELEVATIONS REFERENCED TO THE CHART DATUM OF EACH 

Superior

602.69

183.70

603.02

183.80

603.22

183.86

1985

600.46

183.02

2007

602.17183.54

MichHuron

580.51

176.94580.48176.93

581.96

177.38

1986

576.64

175.76

1964

579.10

176.51

St.

Clair

576.18175.62576.05175.58

576.90

175.84

1986

571.98174.34

1934

574.44175.09

Erie

573.03

174.66

572.80

174.59573.59174.83

1986

568.83173.38

1934

571.42174.17

Ontario

245.18

74.73

246.33

75.08

247.41

75.41

1947

242.49

73.91

1934

245.21

74.74

SEPTEMBER 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) 226-6442 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

September 2018

According to preliminary estimates, precipitation within the Great Lakes basin was 11% below average in September. 

All the individual lake basins saw near to below average precipitation during the month. Lake Superior was the only 

lake to reach average precipitation for the month, receiving 3.52 inches of rain. Lakes Michigan-Huron, Erie, and 

Ontario saw 83%, 87%, and 87% of average precipitation in September, respectively. Despite near to below average 

precipitation, water supplies to the lakes were above average for all the lakes, except Lake Ontario. Outflows from 

all lakes continued to be above average during the month of September. 

September monthly mean water levels were above their long-term average for all lakes, except Lake Ontario. From

August to September, Lake Superior rose 2 inches, while the rest of the lakes declined. Lakes Michigan-Huron and 

St. Clair fell by less than an inch, while Lake Erie and Lake Ontario declined by 2 and 7 inches, respectively. Lake 

Superior’s monthly mean level for September was 4 inches below what it was last year and Lake Ontario was 14 

inches below its level from a year ago. Lake St. Clair and Lake Erie were above their levels from last year by 2 and 

3 inches, respectively, while Lake Michigan-Huron was near its level from a year ago.

PRELIMINARY PRECIPITATION (INCHES)

BASIN

September 12-Month Comparison

2018 Average Diff. % of 

Average

Average Last 

12 Months

Average Diff. % of 

(1900-2016) (1900-2016) Average

Superior 3.52 3.51 0.01 100 27.63 30.58 -2.95 90

Michigan-Huron 2.84 3.44 -0.60 83 30.77 32.55 -1.78 95

Erie 2.82 3.23 -0.41 87 35.43 35.62 -0.19 99

Ontario 2.85 3.28 -0.43 87 35.03 35.87 -0.84 98

Great Lakes 3.02 3.41 -0.39 89 30.95 32.77 -1.82 94

 LAKE September WATER SUPPLIES1 (cfs) September OUTFLOW2 (cfs)

2018

Average

(1900-2008) 2018

Average3

(1900-2008)

Superior 131,000 70,000 92,000 83,000

Michigan-Huron 31,000 27,000 214,000 195,000

Erie -8,000 -17,000 234,000 204,000

Ontario -5,000 5,000 286,000 249,000

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