Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2009

NOV

1945

DEC

1945

2010

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

1973

JUN

1952

JUL

1947

AUG

1947

SEP

1947

OCT

1945

NOV

19451934

DEC

19451934

2011

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

2012

JAN

1946

1935

FEB

1952

1936

MAR

19521935

APR

19731935

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

2009

NOV

1986

DEC

1986

2010

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

1934

DEC

1986

1934

2011

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

2012

JAN

19871935

FEB

1987

1936

MAR

1986

1934

APR

1985

CHART DATUM 569.2 FEET (173.5 METERS) 1934

Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2009

NOV

1986

DEC

1986

2010

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

SEP

1986

OCT

1986

NOV

1986

1934

DEC

1986

1964

2011

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

2012

JAN

19861936

FEB

19861926

MAR

1986

1934

APR

19861926 CHART DATUM 572.3 FEET (174.4 METERS)

ELEVATIONS REFERENCED TO THE CHART DATUM OF EACH 

Superior

601.08

183.21

601.02183.19603.38

183.91

1985

600.72

183.10

1925

602.07

183.51

MichHuron

577.69176.08

577.66

176.07582.35

177.50

1986

576.44

175.70

1964

578.90

176.45

St.

Clair

574.21

175.02573.65174.85

577.30

175.96

1986

571.75174.27

1934

574.11

174.99

Erie

571.75174.27570.77173.97573.95174.94

1986

568.57

173.30

1934

571.06174.06

Ontario

244.95

74.66

244.78

74.61

246.78

75.22

1945

242.19

73.82

1934

244.78

74.61

OCTOBER MEAN LAKE LEVELS

(IGLD 1985)

* 2011 Ft.

M.

2010 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional** Average, Maximum and Minimum for period 1918-2010

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. Tables of possible storm-induced rises at key locations on the 

Great Lakes are available on request. The Corps also publishes the "Great Lakes, Connecting Channels and St. 

Lawrence River Water Levels and Depths,” weekly, which provides a forecast of depths in the connecting rivers 

between the Great Lakes and the International Section of the St. Lawrence River. Internet address 

http://www.lre.usace.army.mil/glhh contains this information on the Internet. 

Great Lakes Basin Hydrology

October 2011

The Lake Superior basin experienced below average precipitation in October, while the Lake Michigan-Huron, Lake Erie 

and Lake Ontario basins received above average precipitation. Over the past 12 months, Lake Superior received below 

average precipitation, while Lake Michigan-Huron has received above average precipitation. Above average 

precipitation also fell on the Lake Erie and Lake Ontario basins over the last 12 months. Precipitation over the entire 

Great Lakes basin was above average in October and above average over the past 12 months. In October, the net 

supply of water to the Lake Superior basin was below average, while it was above average to the Lake Michigan-Huron, 

Lake Erie and Lake Ontario basins. The tables below list October precipitation and water supply information for all 

Great Lakes basins. 

A comparison of October monthly mean lake levels to long-term average (1918-2010) shows Lakes Superior and 

Michigan-Huron were 12 and 15 inches, respectively, below average. While, Lakes St. Clair, Erie and Ontario were 1, 8 

and 2 inches, respectively, above average in October. Boaters should be aware of hazards to navigation due to 

continued below average water levels on the upper lakes. 

 

PRECIPITATION (INCHES) 

BASIN 

October 12-Month Comparison 

2011 Average Diff. % of 

Average 

Last 12 

months 

Average Diff. % of 

(1900-2008) (1900-2008) Average 

Superior 2.31 2.86 -0.55 81 28.91 30.51 -1.60 95 

Michigan-Huron 3.33 2.87 0.46 116 34.22 32.44 1.78 105 

Erie 4.38 2.77 1.61 158 48.05 35.40 12.65 136 

Ontario 4.01 3.10 0.91 129 40.18 35.71 4.47 113 

Great Lakes 3.28 2.88 0.40 114 35.43 32.64 2.79 109 

 

 LAKE 

October WATER SUPPLIES1

 (cfs) October OUTFLOW2 (cfs) 

2011 

Average4

(1900-1989) 2011 

Average3

(1900-1999)

Superior -6,000 40,000 55,000 80,000 

Michigan-Huron 88,000 1,000 172,000 191,000 

Erie 25,000 -21,000 215,000 201,000 

Ontario 24,000 7,000 260,000 243,000 

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

1

 Negative water supply denotes evaporation from lake exceeded runoff from local basin. 

2

 Does not include diversions. 

3

 Niagara and St Lawrence rivers average outflows are based on period of record 1900-1989 and 1900-2005, respectively 

4 Lakes Erie and Ontario average water supplies based on 1900-1989