Ft.

-1

0

+ 1

+ 2+ 3+ 4+ 5

M.

-0.3

0

+ 0.3

+ 0.6

+ 0.9+ 1.2+ 1.5

2017

SEP

1947

OCT

1945

NOV

1945

DEC

1945

2018

JAN

1946

FEB

1952

MAR

1952

APR

1973

MAY

2017

JUN

2017

JUL

2017

AUG

1947

SEP

19471934

OCT

19451934

NOV

19451934

DEC

19451934

2019

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

2020

JAN

1946

1935

FEB

1952

1936

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

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2018

JAN

1987

FEB

1987

MAR

1986

APR

1985

MAY

1986

JUN

1986

JUL

1986

AUG

1986

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

JUL

1986

1934

AUG

1986

1934

SEP

1986

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1934

2020

JAN

19871935

FEB

1987

1936

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

SEP

1986

OCT

1986

NOV

1986

DEC

1986

2018

JAN

1986

FEB

1986

MAR

1986

APR

1986

MAY

1986

JUN

1986

JUL

1986

AUG

1986

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

JUL

1986

1934

AUG

1986

1934

SEP

1986

1934

OCT

1986

1934

NOV

1986

1934

DEC

1986

1964

2020

JAN

19861936

FEB

19861926

CHART DATUM 572.3 FEET (174.4 METERS)

ELEVATIONS REFERENCED TO THE CHART DATUM OF EACH 

Superior

603.22

183.86

602.53183.65603.22

183.86

1952

600.43

183.01

2007

602.17183.54

MichHuron

581.76

177.32580.54176.95581.99177.39

1986

576.67175.77

1964

579.27

176.56

St.

Clair

577.30

175.96

576.25175.64

577.10175.90

1986

572.21174.41

1934

574.67

175.16

Erie

574.21

175.02573.23174.72573.95174.94

1986

569.00

173.43

1934

571.75174.27

Ontario

247.80

75.53

245.77

74.91

247.97

75.58

1947

242.78

74.00

1934

245.70

74.89

AUGUST MEAN LAKE LEVELS

(IGLD 1985)

* 2019 Ft.

M.

2018 Ft.

M.

** MAX.

Ft.

M.

Yr.

** MIN.

Ft.

M.

Yr.

** AVG. Ft.

M.

* provisional** Average, Maximum and Minimum for period 1918-2018

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 monthly mean 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

August 2019

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

month of August. Only Lake Erie received above average precipitation. All lakes received below average water 

supplies for the month of August as a result of the dryer conditions coupled with some increased evaporation. 

Outflows for all lakes continued to be above average during August, with preliminary estimates showing that outflows 

through all but the St. Marys River continue to be above record highs.

Lakes St. Clair and Erie experienced their highest August monthly mean water levels dating back to 1918. Lake 

Superior tied its record high monthly mean water level for August, which was last set in 1952. From July to August, 

the monthly mean levels dropped for all Great Lakes, except Lake Superior which remained at approximately the 

same monthly mean level. Seasonal declines are underway on all the Great Lakes, but extremely high levels are 

forecasted to continue over the next several months.

PRECIPITATION (INCHES)

BASIN

August 12-Month Comparison

2019

Average

Diff. % of 

Average

Last 12 

months 

Average

Diff. % of 

(1900-2016) (1900-2016) Average

Superior 2.19 3.16 -0.97 69 28.90 30.58 -1.68 95

Michigan-Huron 2.12 3.13 -1.01 68 32.89 32.55 0.34 101

Erie 3.31 3.22 0.09 103 38.51 35.62 2.89 108

Ontario 2.91 3.14 -0.23 93 37.89 35.87 2.02 106

Great Lakes 2.39 3.15 -0.76 76 33.04 32.77 0.27 101

 LAKE

August WATER SUPPLIES1(cfs) August OUTFLOW2

(cfs)

2019

Average

(1900-2008) 2019

Average3

(1900-2008)

Superior 62,000 94,000 112,000 83,000

Michigan-Huron -14,000 53,000 252,000 195,000

Erie -24,000 -10,000 269,000 209,000

Ontario -2,000 8,000 364,000 256,000

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