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LEVELnews

Volume 19, Number 4

April 12, 2011

Wet Weather Helps Move Lakes Erie and Ontario Water Levels Closer to Average During March

The wet weather that began late in February over the basins of lakes Erie and Ontario continued into March. As a result of both the rainfall and the related basin runoff, the water supplies received by both lakes were well above average during March. This resulted in the levels of lakes Erie and Ontario rising by 27 and 33 cm, respectively. These increases are more than twice their respective 1918-2010 period-of-record average increases for March, of 13 and 15 cm, respectively.

Due to these larger-than-average increases, the levels of lakes Erie and Ontario moved closer to their averages during March. As indicated in the water level information table provided below, lakes Erie and Ontario began April just a few centimetres below average, and higher than they were at the same time in 2010.

Water levels on lakes Superior and Michigan-Huron did not experience similar increases relative to average conditions during March. The level of Lake Superior fell a bit further below average during March, by 4 cm – or twice its average decline of 2 cm for the month – in response to water supplies well below average during the month. The level of Lakes Michigan-Huron did move 1 cm closer to average during March, with its increase of 6 cm during the month being 1 cm more than its average increase of 5 cm. This occurred in response to near-average water supply conditions.

As indicated in the water level information table, the levels of lakes Superior and Michigan-Huron remain well below their respective 1918-2010 period-of-record average levels, and also below their levels at the same time last year.

Water Levels Forecast

The level of Lake Superior is expected to increase gradually during April as it begins its annual seasonal rise, which is typical for this month. Water levels on lakes Michigan-Huron, Erie and Ontario are also expected to increase in April as these lakes continue their normal annual seasonal climbs.

For a complete range of probable water levels over the next six months on each of the Great Lakes and on Lake St. Clair, please refer to the March 2011 edition of the Canadian Hydrographic Service’s monthly water levels bulletin, found at: www.waterlevels.gc.ca/C&A/tidal_e.html.

What a Difference a Month Can Make

The significant change in water level conditions on lakes Erie and Ontario during March is a good example of why it is important to check the Canadian Hydrographic Service’s monthly bulletin at the beginning of each month to obtain an update on current and forecasted water level conditions.

As noted earlier, the levels of lakes Erie and Ontario are now just a few centimetres below average and higher than they were at the same time last year At the beginning of March, both of these lakes were approximately 20 cm below average, and lower than they were one year earlier. Although the latest forecast indicates that water levels on both lakes are still likely to be below average throughout the spring and summer, because of the increase in levels they experienced during March the possibility of them reaching average levels or higher has increased.

Ice Boom Removal Delayed Past April 1

Ice cover conditions on the eastern end of Lake Erie delayed the removal of the Lake Erie-Niagara River Ice Boom beyond April 1.

The International Joint Commission’s current Order of Approval governing the operation of the ice boom requires that all floating sections of the boom be opened by the first day of April unless there are more than 650 square kilometres of ice remaining on eastern Lake Erie. An aerial observation on March 30 indicated that ice still covered 1,580 square kilometres of the eastern basin of the lake.

Great Lakes Water Level Information

	March 2011 Monthly Mean Level		Beginning-of-April 2011 Level
Lake	Compared to Monthly Average (1918-2010)	Compared to  One Year Ago	Compared to Average (1918-2010) Beginning-of-Month	Compared to  One Year Ago
Superior	36 cm below	22 cm below	37 cm below	22 cm below
Michigan- Huron	50 cm below	28 cm below	49 cm below	25 cm below
St. Clair	23 cm below	9 cm below	18 cm below	2 cm below
Erie	4 cm below	6 cm above	4 cm below	6 cm above
Ontario	7 cm below	6 cm above	3 cm below	10 cm above

March Precipitation over the Great Lakes *

Great Lakes Basin 107%
Lake Superior 60%
Lakes Michigan-Huron 108%
Lake Erie (Including Lake St. Clair) 140%
Lake Ontario 131%

March Outflows from the Great Lakes *

Lake Superior 79%    
Lake Huron 83%        
Lake Erie 101%
Lake Ontario 101%

* As a percentage of the long-term March average.

Note:  These figures are preliminary