LEVELnews: Great Lakes and St. Lawrence River water levels, July 2023
Lakes Superior, Michigan-Huron, and Erie Basins experience dry conditions
During June, the Great Lakes Basin experienced the following:
- The mean monthly water levels of all the Great Lakes were above average. It is worth noting that Lake Superior experienced its eighth highest average water level for June even though it received very dry water supply conditions (a combination of the precipitation, evaporation, and runoff).
- In fact, the water supply conditions experienced by all the lakes, except Lake Ontario were either lower or much lower than average. Only Lake Ontario’s water supplies were close to average.
- June precipitation amounts were much less than average for Lakes Superior and Michigan-Huron. Lakes Erie and Ontario experienced closer to average precipitation amounts.
- Due to the generally dry conditions in the basin, all the lakes either rose less or declined more than their averages. Lake Superior experienced its fourth smallest rise on record while Lake Michigan-Huron experienced its ninth smallest change on record.
This is the time of year when the water levels of Lakes Superior and Michigan-Huron are typically still rising, and when both Lake Erie and Ontario have peaked or will soon peak and have begun their seasonal decline.
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.
Rip currents can be dangerous hazards while swimming anywhere in the Great Lakes, find out more information about them below.
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Lake |
Levela |
Compared to June monthly average (1918–2022) |
Compared to June 2022 |
Compared to record high (1918-2022) |
Notes |
|---|---|---|---|---|---|
Superior |
183.68 m |
23 cm above |
11 cm above |
16 cm below |
eighth highest on record |
Michigan–Huron |
176.68 m |
11 cm above |
13 cm below |
76 cm below |
- |
St. Clair |
175.46 m |
26 cm above |
9 cm below |
56 cm below |
- |
Erie |
174.60 m |
23 cm above |
8 cm below |
54 cm below |
- |
Ontario |
75.24 m |
18 cm above |
11 cm above |
67 cm below |
- |
a 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
Lake |
June lake level change |
June monthly average change (1918-2022) |
Compared to average June change (1918-2022) |
Notes |
|---|---|---|---|---|
Superior |
1 cm rise |
7 cm rise |
less than average rise |
fourth smallest rise on record |
Michigan–Huron |
no change |
5 cm rise |
less than average rise |
ninth smallest change on record |
St. Clair |
4 cm rise |
4 cm rise |
less than average rise |
- |
Erie |
4 cm decline |
2 cm rise |
less than average rise |
- |
Ontario |
10 cm decline |
1 cm decline |
Much more than average decline |
- |
a Lake 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 July beginning-of-month average (1918–2022) |
Compared to July 2022 |
Compared to record high (1918-2022) |
Notes |
|---|---|---|---|---|---|
Superior |
183.69 m |
20 cm above |
9 cm above |
17 cm below |
- |
Michigan–Huron |
176.69 m |
10 cm above |
13 cm below |
77 cm below |
- |
St. Clair |
175.48 m |
27 cm above |
6 cm below |
58 cm below |
- |
Erie |
174.58 m |
21 cm above |
6 cm below |
60 cm below |
- |
Ontario |
75.20 m |
14 cm above |
16 cm above |
71 cm below |
- |
a At the beginning of July, all of the Great Lakes were at least 49 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 well 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 in mid to late summer, while very dry conditions could result in lake levels approaching 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 the end of the summer.
Lake Erie is also expected to stay above average under most water supply scenarios.
Lake Ontario is above average but may approach average by late summer 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 results 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 |
Net basin supply |
Outflows |
|---|---|---|---|
Superior |
64% |
88% (very dry) |
134% |
Michigan-Huron |
56% |
96% (extremely dry) |
107% |
Erie |
82% |
84% (very dry) |
109% |
Ontario |
99% |
51% (average) |
117% |
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.
d Please 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.
Be aware of rip currents when swimming on the lakes
Rip currents can occur in the Great Lakes whenever waves push water toward the shore. Breaking waves create a buildup of water along the shoreline that at some point needs to flow back toward the lake. Rip currents can develop where there is a low point in the lake bottom just off shore, such as a sand bar or rock reef, which funnels the water back toward the lake. Rip currents can be dangerous as they can pull even strong swimmers out into deep water; however, contrary to common belief, rip currents do not have an undertow and will not pull swimmers underwater.
Understanding rip currents and the conditions that cause them to form can help make it possible to avoid them altogether or for strong swimmers to safely exit them. To help make your summer activities around the Great Lakes safe and enjoyable please look for further information on Great Lakes rip currents here: Learn about hurricanes: hazards and impacts - Canada.ca.
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
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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