LEVELnews: Great Lakes and St. Lawrence River water levels, December 2024

Lake Superior Basin experiences wet November, while the other basins experienced dry water supply conditions

In November, the Great Lakes Basin experienced the following:

• The mean monthly water level of Lakes Superior, Michigan-Huron, and Ontario were below average, while Lakes St. Clair and Erie were above average.
• Lake Superior experienced wet water supply conditions (a combination of the precipitation, evaporation, and runoff), while the other lakes had dry to very dry conditions.
• Lake Superior received higher than average November precipitation, and Lake Michigan-Huron had precipitation amounts that were closer to average. Both Lakes Erie and Ontario received below average precipitation.
• Most of the Great Lakes experienced greater than average monthly declines, while the decline of Lake Superior was slightly less than average.

With average water supplies for this time of year, some of the lakes are expected to continue their seasonal decline while others may hold steady or begin their seasonal rise in the coming months.

Low-lying areas are at risk for accelerated coastline erosion and flooding with the increased possibility of large storms and stronger winds in the fall months. For current information and forecasts, please refer to the sources listed at the end of this newsletter.

Find out about the plans for the annual installation of the Lake Erie – Niagara River ice boom below.

Get notified when a new edition of LEVELnews is available!

Did you know that you can be notified whenever a new edition of LEVELnews is available? Visit the LEVELnews subscription page to sign up for email notifications. You can unsubscribe at any time.

¹ Water levels are referenced to International Great Lakes (Vertical) Datum 1985 (IGLD85). For more information, please visit International Great Lakes Datum Update – Great Lakes Coordinating Committee.

¹ Lake level changes are based on the differences in levels at the beginning of the month, not the monthly average levels.

¹ At the beginning of December, all the Great Lakes were at least 11 cm above their chart datum level. Chart datum is a reference elevation for each lake that provides more information on the depth of water for safe boat navigation on the lakes. For more information, please visit Low Water Datum – Great Lakes Coordinating Committee.
² Water levels are referenced to International Great Lakes (Vertical) Datum 1985 (IGLD85). For more information, please visit International Great Lakes Datum Update – Great Lakes Coordinating Committee.

Water levels forecast

Lake Superior ended the month below its average level and is expected to remain so under most water supply conditions.

Lake Michigan-Huron is expected to remain below average under typical and drier than average water supply conditions. However, wetter than average conditions would result in close to average water levels.

Lake Erie is expected to stay above average under most water supply scenarios. It would take dry water supply conditions for lake levels to fall below average by the end of the year.

Lake Ontario water levels are expected to remain below average under typical water supply conditions. However, wetter than average water supply conditions may result in above average lake levels in the next few months.

For more information on the probable range of water levels, consult the LEVELnews note on projections.

For a graphical representation of recent and forecasted water levels on the Great Lakes, refer to the Canadian Hydrographic Service’s monthly water levels bulletin.

¹ As a percentage of long-term average (LTA).
² Environment and Climate Change Canada – Canadian Precipitation Analysis System. For more information, please visit: Technical documentation: Regional Deterministic Precipitation Analysis.
³ <5% extremely wet; <25% very wet; <45% wet; 45-55% average; >55% dry; >75% very dry; >95% extremely dry.
⁴ Please refer to the LEVELnews – What is net basin supply for a description of net basin supply.

Note: The information contained in this report is provisional and is subject to change. Data are calculated from the best available observations at the time of posting.

Lake Erie – Niagara River ice boom installation planned to begin in December

Installation of the ice boom for the 2024-2025 ice season is scheduled to begin as early as December 16, 2024, by the New York Power Authority (NYPA) crews, subject to safe in-water working conditions.

Each winter since 1964, the Lake Erie – Niagara River ice boom has been installed near the outlet of Lake Erie to reduce the amount of ice entering the Niagara River. A reduction in ice entering the river reduces the potential for ice jams, which can result in damage to shoreline property and significantly reduce water flow for hydroelectric power production.

In accordance with the International Joint Commission’s (IJC) 1999 Supplementary Order of Approval, placement of the spans may begin when the Lake Erie water temperature at Buffalo reaches 4 degrees Celsius or on December 15, whichever comes first. As of early December, Lake Erie water temperature at Buffalo, NY is 7 degrees Celsius.

The ice boom is installed at the outlet of Lake Erie, at the entrance to the Niagara River, to promote the formation and strengthening of a naturally occurring ice arch that reduces the amount of ice entering the Niagara River. The ice boom has substantially reduced the severity, number, and duration of ice runs from Lake Erie into the Niagara River that have potential to cause ice jams, damage shoreline property and reduce the capacity for water diversion to generate hydropower.

Severe storms with westerly winds can overcome the stability of the ice arch and force large masses of ice against the boom. When this occurs, the ice boom submerges and allows the ice to override it until the pressure is relieved. Once the storm subsides, the ice boom resurfaces and restrains ice that otherwise would flow down the river. The ice boom does not inhibit the flow of water from the lake into the Niagara River, which flows under the ice.

Visit the Board’s webpage to learn more about the ice boom.

Flood information

Great Lakes water levels are difficult to predict weeks in advance due to natural variations in weather. To stay informed about Great Lakes water levels and flooding, visit the Ontario flood forecasting and warning program.

Additional information can be found on the International Lake Superior Board of Control website and the International Lake Ontario–St. Lawrence River Board website.

Information on current water levels and marine forecasts

Monthly levels: Fisheries and Oceans Canada produces the Monthly Water Level Bulletin for the Great Lakes and Montréal Harbour. On this page you will find a link to the full bulletin PDF. This publication complements the information provided by LEVELnews monthly.

Daily levels: Current daily average levels of all the Great Lakes are available at Great Lakes – Daily Water Levels for This Month in Meters. The daily average water level is taken from several gauges across each lake and is a good indicator of the overall lake level despite local rises or falls in water levels owing to factors like high precipitation, wind and waves.

Hourly levels: Hourly lake levels from individual gauge sites can be found at the Government of Canada Great Lakes water level gauging stations map. These levels are useful for determining real-time water levels at a given site; however, it should be noted that they are subject to local, temporary effects on water levels such as wind and waves.

Marine forecasts: Visit the “Wave and wind data” section of the Great Lakes water levels and related data webpage for marine forecasts and wave heights. Current marine forecasts for Lakes Superior, Huron, Erie and Ontario are available as well as text bulletins of recent wave height forecasts.

For more information

Frank Seglenieks (Editor) and Sarah Fettah
Boundary Water Issues
National Hydrological Service
Meteorological Service of Canada
Environment and Climate Change Canada
Burlington, ON  L7S 1A1

Email: LEVELnews-infoNIVEAU@ec.gc.ca