LEVELnews

Great Lakes - St. Lawrence River Water Levels
Volume 19, Number 11

14 November 2011

Low Supply Conditions Persist for Lake Superior

Water levels fell on each of the Great Lakes during October as the lakes continue their seasonal declines. However, wet weather during October resulted in smaller-than-average declines on lakes Michigan–Huron, Erie and Ontario during the month.

Although outflows from Lake Superior were below average during October, the below-average water supplies it received caused the lake’s level to fall by 5 cm this October. That amount is 1 cm more than its average October decline of 4 cm. In contrast to Lake Superior, the levels of lakes Michigan–Huron, Erie and Ontario each fell by less than average amounts during October, in response to above-average water supplies. The level of Lakes Michigan–Huron fell by just 2 cm during October, 5 cm less than its 1918–2010 period-of-record average decline for the month. The levels of lakes Erie and Ontario fell by 6 and 5 cm, respectively, during October--3 and 7 cm less than their average October declines of 9 and 12 cm, respectively.

As indicated by the beginning-of-November differences provided in the water level information table provided below, the levels of lakes Superior and Michigan–Huron remain more than 30 cm below their respective averages for the 1918–2010 period of record. Both lakes are, however, a bit higher than they were at the same time last year. In addition, due to its smaller-than-average water level decline during October, the level of Lakes Michigan–Huron is 5 cm closer to its long-term average level than it was at the beginning of October.

Great Lakes Water Level Information
	October 2011 Monthly Mean Level		Beginning-of-November 2011 Level
Lake	Compared to Monthly Average (1918–2010)	Compared to One Year Ago	Compared to Beginning-of-Month Average (1918–2010)	Compared to One Year Ago
Superior	30 cm below	2 cm above	31 cm below	2 cm above
Michigan-Huron	37 cm below	1 cm above	32 cm below	7 cm above
St. Clair	3 cm above	17 cm above	6 cm above	20 cm above
Erie	21 cm above	30 cm above	24 cm above	34 cm above
Ontario	5 cm above	5 cm above	9 cm above	9 cm above

Six-Month Forecast

The levels of each of the Great Lakes and Lake St. Clair are expected to fall during November as the lakes continue their annual seasonal declines.

For a graphical representation of recent and forecasted water levels on each of the Great Lakes and on Lake St. Clair, compared to their 1918–2010 period-of-record monthly averages and extreme levels, please refer to the October 2011 edition of the Canadian Hydrographic Service’s monthly water levels bulletin.

Lake Ontario Outflow Strategy

The International St. Lawrence River Board of Control recently reviewed conditions in the Lake Ontario–St. Lawrence River system. The Board has decided to continue to release outflows as specified by the lake’s current regulation plan: Plan 1958-D. The Board may vary outflows to meet critical hydropower, navigational or other needs. As the levels on Lake Ontario are currently following their seasonal decline, the Board intends to retain the 2.7 cm of water currently stored on the lake and release this water during the winter. The Board, in conjunction with its staff, continues to monitor conditions carefully and is prepared to take further action as required.

October Precipitation over the Great Lakes*
Great Lakes Basin	112%	Lake Erie	151%
Lake Superior	70%	(including Lake St. Clair)
Lakes Michigan-Huron	123%	Lake Ontario	122%
October Outflows from the Great Lakes*
Lake Superior	69%	Lake Erie	108%
Lake Huron	90%	Lake Ontario	108%

*As a percentage of the long-term 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

David Fay
Great Lakes - St. Lawrence
Regulation Office
MSC - Operations Ontario
Environment Canada
111 Water Street East
Cornwall ON  K6H 6S2
Tel.: 613-938-5725

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