Great Lakes – St. Lawrence River Information

Great Lakes’ water movement, water levels and historical data.

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Water level bulletin and forecast

Monthly water level bulletin

Monthly water levels for the Great Lakes area and Montréal Harbour.

Water levels forecast

Water levels forecast for the Great Lakes.


Back issues of water levels bulletin

Browse past issues of the monthly water levels for the Great Lakes area and Montréal Harbour.


Services and information

The tide and water level gauge network

Description of and data from network of tide and water level gauges in the Great Lakes.

Great Lakes-St. Lawrence River system

Description of the lakes and channels that make up the Great Lakes-St. Lawrence River system.


Water circulation

Description of the circulation of water in the Great Lakes.


Fluctuations in water levels

Description of changes in water levels in the Great Lakes with historical charts.


Natural factors affecting water levels

How factors like precipitation and evaporation effect water levels in the Great Lakes.

Great Lakes Monthly Mean Water Level

Monthly mean water level in metres referred to chart datum.


Historical Great Lakes water level data

Historical monthly mean water levels for each of the Great Lakes from 1918 to 2016.


What we are doing


CHS Digital Transformation Initiative

CHS Digital Transformation Initiative

At the Canadian Hydrographic Service, innovation is a guiding principle for the bold digital transformation initiative now underway.

Supporting women in hydrography

Supporting women in hydrography

Enabling more women to participate equitably and assume more leadership roles in the field of hydrography.

2022 Tide Tables Available Now

2022 Tide Tables Available Now

Download your 2022 Canadian Tide and Current Tables now to help navigate safely through Canadian waters.