Great Lakes – St. Lawrence River Information

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

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Water levels data

Monthly water levels bulletin

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

Monthly Water levels forecast

Water levels forecast for the Great Lakes.


Monthly Historical Great Lake Means

Historical monthly mean water levels for each of the Great Lakes.

Hourly water levels

Hourly water levels for the Great Lakes provided by the Marine Environmental Data Service.


Water level data web services

Web services for accessing official data on navigating modelled surface currents and water levels.


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.


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.

NONNA Version 3.0 Release

NONNA Version 3.0 Release

Client suggested enhancements have been implemented to the CHS NONNA Data Portal including migration to chart datum and enhanced tools for selecting and downloading large geographic areas.

2024 Tide Tables Available Now

2024 Tide Tables Available Now

Download your 2024 Canadian Tide and Current Tables now to help navigate safely through Canadian waters.