LEVELnews
Great Lakes–St. Lawrence River Water Levels
Volume 21, Number 6
13 June 2013
May 2013 Sees Large Rise in Lake Superior's Level
Relatively wet conditions were experienced in the northern part of the Great Lakes basin during May, especially on Lake Superior, where significant snowmelt coupled with above-average precipitation resulted in a rapid rise in water levels. A different story played out in the southern-most parts of the basin, where conditions were relatively dry, particularly on Lake Erie. Downstream of the Great Lakes, Montreal Harbour levels were below average for most of the month, but rose sharply near the end of May, finishing the month above average.
- Water supplies to Lake Superior were the second highest recorded in the month of May since 1918. This, along with below-average outflows, resulted in Lake Superior’s level rising by 24 cm during May, 15 cm more than the lake’s 1918–2012 period of record average rise of 9 cm, and the lake’s second largest May rise on record (the largest being 27 cm in May of 1950).
- After an extremely wet April, Lake Michigan–Huron experienced relatively wet conditions again in May, rising 13 cm, 5 cm more than its average May rise of 8 cm.
- In contrast to the uppermost lakes, relatively dry conditions caused Lake Erie to remain at about the same level from the beginning to the end of the month, while on average the level of Lake Erie has risen by 5 cm during the month of May over the 1918–2012 period of record.
- On Lake Ontario, below-average outflows helped offset below-average water supplies, and this saw the lake rise 9 cm, slightly more than its average May rise of 8 cm.
- The monthly mean level at Montreal Harbour was 17 cm below average, but 79 cm higher than May’s level last year. Daily water levels at Montreal Harbour fell during the first three weeks of May as spring outflows from the Ottawa River subsided. Precipitation late in the month saw levels rebound, rising sharply near the end of May.
| Lake | Compared to Monthly Average (1918–2012) | Compared to One Year Ago |
|---|---|---|
| Superior | 25 cm below | 5 cm above |
| Michigan–Huron | 55 cm below | 12 cm below |
| St. Clair | 28 cm below | 14 cm below |
| Erie | 20 cm below | 17 cm below |
| Ontario | 13 cm below | 3 cm below |
| Lake | Compared to Beginning-of-Month Average (1918–2012) | Compared to One Year Ago |
|---|---|---|
| Superior | 18 cm below | 8 cm above |
| Michigan–Huron | 50 cm below | 3 cm below |
| St. Clair | 22 cm below | 9 cm below |
| Erie | 20 cm below | 14 cm below |
| Ontario | 11 cm below | 4 cm above |
Water Level Forecast
Relative to their beginning-of-June levels and assuming average water supply conditions, all of the lakes are expected to continue their typical seasonal rise in June. Assuming average water supplies, forecasts indicate that Montreal Harbour’s monthly mean level in June is expected to fall, as is typical for this time of year, but remain above chart datum.
For a graphical representation of recent and forecasted water levels on each of the Great Lakes, Lake St. Clair and Montreal Harbour compared to their respective period-of-record monthly averages and extreme levels please refer to the May 2013 edition of the Canadian Hydrographic Service’s monthly water levels bulletin.
Water Levels
Real-time water levels on the Great Lakes, their connecting channels and the upper St. Lawrence River are available by telephone from a network of gauging stations operated by the Canadian Hydrographic Service (CHS). Please visit the CHS website for a list of voice-announcing water level gauging stations and their telephone numbers.
| Lake | % |
|---|---|
| Great Lakes Basin | 115% |
| Lake Superior | 157% |
| Lake Michigan–Huron | 110% |
| Lake Erie (including Lake St. Clair) | 77% |
| Lake Ontario | 91% |
| Lake | % |
|---|---|
| Lake Superior | 75% |
| Lake Michigan–Huron | 90% |
| Lake Erie | 93% |
| Lake Ontario | 87% |
*As a percentage of the long-term May average.
Note: These figures are preliminary.
For more information:
Chuck Southam (Editor)
Boundary Water Issues Unit
MSC - Operations Ontario
Environment Canada
P.O. Box 5050
Burlington ON L7R 4A6
Tel.: 905-336-4955
Fax: 905-336-8901
Email: water.levels@ec.gc.ca
Jacob Bruxer
Great Lakes–St. Lawrence Regulation Office
MSC - Operations Ontario
Environment Canada
111 Water Street East
Cornwall ON K6H 6S2
Tel.: 613-938-5725
- Date Modified: