Monthly Water Level Bulletin


A newsletter, LEVELnews published by Environment Canada is included with the bulletin.

Canada/US flagA network of gauging stations on both sides of the border on each lake is used to determine the average water level for the month. The following stations are used:

Lake Superior at: Thunder Bay, Michipicoten, Duluth, Marquette and Point Iroquois

Lakes Michigan/Huron at: Thessalon, Tobermory, Milwaukee, Ludington, Mackinaw City and Harbor Beach

Lake St. Clair at: Belle River and St. Clair Shores

Lake Erie at: Port Stanley, Port Colborne, Toledo and Cleveland

Lake Ontario at: Port Weller, Toronto, Cobourg, Kingston, Rochester and Oswego

Additional Sources of Information:

Water Levels

December 2021

Great Lakes and Montreal Harbour

Monthly Bulletin prepared by the Canadian Hydrographic Service Fisheries and Oceans Canada

Water Level Advisory

Water Level Advisory

Water levels for Lake Superior, Lake Michigan-Huron, Lake St. Clair, Lake Erie, Lake Ontario and Montréal Harbour are above their all-time average for this time of year and are above the level of Chart Datum.

Mariners should exercise extreme caution throughout the entire system, especially during periods of strong winds when water levels can rise or fall significantly in a short period of time.

December 2021 Graph
December 2021 Graph
Monthly Mean Water Levels in metres referred to IGLD 1985
December 2021 Lake Superior Lake Huron Lake St. Clair Lake Erie Lake Ontario Montréal
Mean for Month (preliminary data) 183.31 176.69 175.42 174.58 74.87 6.64
Mean for month last year 183.63 177.14 175.63 174.65 74.62 6.66
Mean for month, last 10 years 183.50 176.52 175.19 174.30 74.59 6.34
Statistics for period of record 1918-2020 1918-2020 1918-2020 1918-2020 1918-2020 1967-2020
Maximum monthly mean / year 183.81
Mean for month, All Time 183.41 176.36 174.93 174.01 74.53 6.51
Minimum monthly mean / year 182.92
Probable mean for next month 183.27 176.64 175.40 174.58 74.88 6.60
Chart Datum 183.2 176.0 174.4 173.5 74.2 5.55

To convert from metres to feet, divide by 0.3048


The monthly mean levels for the previous year and current year shown on the graphs are the average of water levels recorded at a network of gauging stations on each lake. Historical data from these networks are used to determine the all-time average and the historical extreme monthly levels.

Water levels for the Canadian stations in the networks are collected by the Canadian Hydrographic Service. Six month forecasts of the probable range of future levels are prepared under the auspices of the International Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data by Environment Canada and the Detroit District, Corps of Engineers.

This bulletin is prepared each month as a public service and is available on the World Wide Web at:

Additional information on water levels in the Great Lakes System may be obtained by telephoning the Canadian Hydrographic Service at (877) CHS-LINK (877-247-5465), by fax at (905) 336-8916, or by email at

World Wide Web at: