Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2014

AUG

1947

SEP

1947

OCT

1945

NOV

1945

DEC

1945

2015

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

1973

JUN

1952

JUL

1947

AUG

19471934

SEP

19471934

OCT

19451934

NOV

19451934

DEC

19451934

2016

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

17

JAN

1946

1935

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

2014

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2015

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

1934

SEP

1986

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1934

2016

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

17

JAN

19871935

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

2014

AUG

1986

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2015

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

1934

SEP

1986

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1964

2016

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

17

JAN

19861936

CHART DATUM 572.3 FEET (174.4 METERS)

ELEVATIONS REFERENCED TO THE CHART DATUM OF EACH 

Superior

602.66

183.69602.62183.68603.08183.82

1950

600.26182.96

1926

602.03

183.50

MichHuron

580.18176.84579.82176.73581.99177.39

1986

576.71

175.78

1964

579.30

176.57

St.

Clair

575.75175.49575.98

175.56

577.20

175.93

1986

572.51

174.50

1934

574.77175.19

Erie

572.64174.54573.29174.74574.25175.03

1986

569.06

173.45

1934

571.92174.32

Ontario

245.90

74.95

246.75

75.21

248.23

75.66

1947

243.24

74.14

1934

246.06

75.00

JULY MEAN LAKE LEVELS

(IGLD 1985)

* 2016 Ft.

M.

2015 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional** Average, Maximum and Minimum for period 1918-2015

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

July 2016

According to preliminary estimates, the precipitation over all of the lakes for July was below average. Lake Superior 

and Lake Michigan-Huron were just shy of their average, while Lake Erie and Lake Ontario were well below their 

historical average July precipitation. The net basin supply to Lake Superior was higher than average, while the net 

basin supplies to the rest of the lakes were below average for July. The tables below list July precipitation and water 

supply information for the Great Lakes basin.

The monthly mean level of Lake Superior rose from June to July, while the levels of Lakes St. Clair, Erie, and Ontario 

dropped. Lake Michigan-Huron remained near its June level. All of the lakes were above their long-term average 

(LTA) monthly July levels except Lake Ontario. Superior, Michigan-Huron, St. Clair, and Erie were 7, 11, 12, and 9

inches above their LTA levels, respectively. Lake Ontario was 2 inches below its LTA level. In July, Lake Superior 

was less than an inch higher than it was a year ago and Lake Michigan-Huron was 4 inches above last year’s July

level. Lakes St. Clair, Erie, and Ontario were all below last year’s July level by 3, 8, and 10 inches, respectively.

PRELIMINARY PRECIPITATION (INCHES)

BASIN

July 12-Month Comparison

2016 Average Diff. % of 

Average

Last 12 

Months

Average Diff. % of 

(1900-2012) (1900-2012) Average

Superior 3.24 3.27 -0.03 99 31.85 30.43 1.42 105

Michigan-Huron 2.98 3.03 -0.05 98 32.75 32.48 0.27 101

Erie 2.45 3.39 -0.94 72 31.13 35.59 -4.46 87

Ontario 1.99 3.19 -1.20 62 31.59 35.83 -4.24 88

Great Lakes 2.84 3.15 -0.31 90 32.23 32.68 -0.45 99

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

2016

Average

(1900-2008) 2016

Average3

(1900-2008)

Superior 139,000 129,000 102,000 81,000

Michigan-Huron 93,000 128,000 208,000 195,000

Erie 0 7,000 232,000 209,000

Ontario -5,000 24,000 263,000 261,000

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