LEVELnews: Great Lakes and St. Lawrence River water levels, September 2023
All Lakes except Superior experience wet conditions in August
During August, the Great Lakes Basin experienced the following:
- The mean monthly water levels of all the Great Lakes were above average.
- Lake Superior experienced drier than average water supply conditions, Lake Michigan-Huron’s water supply conditions were wet, while Lakes Erie and Ontario experienced very wet water supply conditions (a combination of the precipitation, evaporation, and runoff).
- August precipitation amounts were below average for Lake Superior but higher than average for the remaining Great Lakes Basins.
- Lakes Superior experienced a lower than average rise, while Lake Michigan-Huron experienced a smaller than average decline. Lake Erie experienced its third largest rise on record, at a time of year when it is usually declines, most of which was a result of a large rain event on the western end of the lake in late August. Finally, Lake Ontario’s level declined close to its average August amount.
This is the time of year where all the lakes have typically reached their annual peaks and started their seasonal declines, aside from Lake Superior that is typically nearing its seasonal peak.
With water levels remaining above average in all lakes, and the possibility of large storms and winds, low-lying areas are at risk for accelerated coastline erosion and flooding. For current information and forecasts, please refer to the sources listed below.
It is the 30th anniversary of LEVELnews! Find out more below about the history of this publication in this month’s edition.
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| Lake | Levela | Compared to August monthly average (1918–2022) | Compared to August 2022 | Compared to record high (1918-2022) | Notes |
|---|---|---|---|---|---|
| Superior | 183.67 m | 13 cm above | 2 cm above | 19 cm below | - |
| Michigan–Huron | 176.70 m | 12 cm above | 9 cm above | 72 cm below | - |
| St. Clair | 175.52 m | 33 cm above | 2 cm above | 45 cm below | - |
| Erie | 174.59 m | 30 cm above | 4 cm above | 43 cm below | - |
| Ontario | 75.06 m | 17 cm above | 32 cm above | 52 cm below | - |
aWater 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.
| Lake | August lake level change | August monthly average change (1918-2022) | Compared to average August change (1918-2022) | Notes |
|---|---|---|---|---|
| Superior | 3 cm decline | 1 cm rise | less than average rise | - |
| Michigan–Huron | 2 cm decline | 4 cm decline | less than average decline | - |
| St. Clair | 1 cm rise | 6 cm decline | less than average decline | - |
| Erie | 1 cm rise | 8 cm decline | less than average decline | - |
| Ontario | 13 cm decline | 14 cm decline | slightly less than average decline | - |
aLake level changes are based on the differences in levels at the beginning of the month and not the monthly average levels.
| Lake | Levela,b | Compared to September beginning-of-month average (1918–2022) | Compared to September 2022 | Compared to record high (1918-2022) | Notes |
|---|---|---|---|---|---|
| Superior | 183.65 m | 10 cm above | 1 cm above | 21 cm below | - |
| Michigan–Huron | 176.68 m | 13 cm above | 8 cm below | 70 cm below | - |
| St. Clair | 175.53 m | 40 cm above | 8 cm above | 42 cm below | - |
| Erie | 174.62 m | 38 cm above | 10 cm above | 32 cm below | - |
| Ontario | 74.99 m |
16 cm above | 33 cm above | 52 cm below | - |
a At the beginning of September, all of the Great Lakes were at least 45 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.
b 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 is currently above its average level and is expected to remain so under most water supply conditions. If there are very wet water supply conditions, lake levels could increase further throughout the fall and winter, while very dry conditions could result in lake levels falling below average.
Lake Michigan-Huron is expected to remain above average under most water supply conditions; it would take very dry conditions to bring the level below average by late fall.
Lake Erie is also expected to stay above average under most water supply scenarios.
Lake Ontario is above average but may come close to an average level by early winter under typical water supply conditions. Wetter than average conditions may result in the level remaining above average, while drier than average water supply conditions would result in the level moving below average.
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.
| Lake | Precipitation (percentage of LTA)a,b |
Net basin supply (probability of exceedance)c,d |
Outflows (percentage of LTA)a |
|---|---|---|---|
| Superior | 93% | 60% (dry) | 116% |
| Michigan-Huron | 115% | 31% (wet) | 106% |
| Erie | 188% | 7% (very wet) | 108% |
| Ontario | 123% | 8% (very wet) | 111% |
a As a percentage of long-term average (LTA).
b Environment and Climate Change Canada – Canadian Precipitation Analysis System
c <5% extremely wet; <25% very wet; <45% wet; 45-55% average; >55% dry; >75% very dry; >95% extremely dry.
dPlease refer to the LEVELnews What is net basin supply for a description of net basin supply.
Note: The figures contained in this report are provisional and are subject to change. Data are calculated from the best available observations at the time of posting.
30 years of Great Lakes level information
The first edition of LEVELnews was issued in September of 1993, and started as an expanded version of a monthly media release prepared by Environment and Climate Change Canada. Of course, back then there were limited ways in which information could be distributed to the public.
At first, the newsletter was printed out and mailed to interested members of the public to augment the monthly water level bulletin produced by Fisheries and Oceans Canada (link below in monthly levels section). In April of 1995 Environment Canada (as we were known then) introduced the “Green Lane” to make environmental information accessible on the internet. From then on, LEVELnews was available on the website and the print edition was discontinued in Oct 2003.
Below is the first page of the first edition, 30 years ago. All editions, starting with September 1993 are available for download. Just like today, the lakes were above their long term averages.
The expertise of the following people have contributed to the publication LEVELnews over the last thirty years. Among them include Ralph Moulton, Peter Yee, Ruth Edgett, Chris Stewart, David Fay, Chuck Southam, Rob Caldwell, Derrick Beach, and Daniel Ferreira.
The current editors, Nicole O’Brien and Frank Seglenieks, are proud to be continuing the fine tradition of LEVELnews to keep the public informed about the Great Lakes water levels and other useful information about the lakes.
Long description
The graphics shows the first page of the first edition of LEVELnews. There are two columns of text with contact information in the box in the middle. The LEVELnews logo is on the top with a picture of the Great Lakes in the top right corner.
Flood Information
With water levels remaining high on some lakes, there is a high risk of flooding. 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 also 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: A monthly water level bulletin, produced by Fisheries and Oceans Canada is available at Monthly Water Level Bulletin for the Great Lakes and Montréal Harbour and click on the link “Full Monthly Water Level Bulletin for the Great Lakes and Montréal Harbour (PDF)”. This publication is intended to complement the information provided by LEVELnews on a monthly basis.
Daily levels: Current daily lake-wide average levels of all the Great Lakes are available at Great Lakes - Daily Water Levels for This Month in Meters (army.mil). The daily average water level is an average taken from several gauges across each lake and is a good indicator of the overall lake level when it is changing relatively rapidly due to recent high precipitation.
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 Great Lakes water levels and related data webpage under the “Wave and wind data” heading 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 Nicole O’Brien
Boundary Water Issues
Meteorological Service Canada
Environment and Climate Change Canada
Burlington, ON L7S 1A1
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