Outflow Strategy
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Copyrights : International St. Lawrence River Board of Control

Lake Ontario Outflow Strategy
(August 19, 2003)

Despite unusually wet weather across much of the system, water levels on the upper Great Lakes remain lower than average and lower than they were a year ago, with the exception of Lake Erie, which as of August 13, was 5 cm (2.0 in.) higher than in 2002. Though its level usually falls by 14 cm (5.5 in.) in August, as of August 13, Lake Ontario had risen 1 cm (0.4 in.) for the month. On August 13, it’s the Lake Ontario level was 75.03 m (246.16 ft.), 14 cm (5.5 in.) above its average for this time of year. Lake St-Louis and Port of Montreal levels have increased since June and, on August 13, were 5 and 9 cm (2.0 and 3.5 in.) above average, respectively. Based upon previous Board action this spring, there is approximately 4.2 cm (1.7 in.) of water conserved on Lake Ontario relative to the level which would have occurred if Plan 1958D was followed exactly.

Forecasts indicate that the Lake Ontario level will remain somewhat above average until at least the second half of October under average water supplies and outflows would be near-normal for the remainder of the year.

The Board reviewed these and other conditions and agreed to maintain the strategy as announced on June 23 and retained in mid-July. The long-term strategy, in consideration of the continued below average levels on the upper Great Lakes, is to have enough water to meet critical needs later in the year within current system constraints.

The short-term strategy is to retain as much of the water conserved on Lake Ontario as possible.

Through the second week of September, outflows will generally be as determined by Regulation Plan 1958-D except for the following deviations:

a) Flow increases to maintain Lake St-Louis level at Pointe-Claire above 20.60 m (67.6 ft.) and the level of Lake St. Francis at Summerstown above 46.58 m (152.82 ft.)

b) Flow increases to meet critical hydropower needs and to raise levels at the Port of Montreal for critical navigation needs at a maximum weekly over-discharge of 300 m3/s (10,600 cfs) and no more than a maximum daily over-discharge of 600 m3/s (21,200 cfs) above Plan flow. A flow change of 300 m3/s will result in a change in level at Montreal of about 10 cm (3.9 inches) and, after a week, a change in Lake Ontario level of about 1 cm (0.4 inch.).

After the Board discussed and updated the strategy last week, and prior to dissemination of this media release, the massive blackout struck. In order to help alleviate the power situation, which was considered an emergency, additional water was released for hydropower production, between Friday morning and Sunday morning. The effect of this outflow increase downstream was to increase the level at the Port of Montreal of approximately 35 cm (14 in.). As of midnight, August 18, the accumulated storage had been reduced to 2.9 cm (1.1 in.) due to these increased flows. The system is now slowly recovering from the black out. However, in response to the state of emergency declared in Ontario, by the Prime Minister of the province, during the next few days the outflow will have to be increased, for short periods of time, to meet hydropower needs.. These flow modifications will increase the levels in Lake St-Louis and the Port of Montreal approximately up to 10 cm (4 in.). They will also decrease the water levels on Lake Saint. Lawrence approximately up to 15 cm (6 in.).

This information can also be found on the Board web site (see below) and will be updated as required.

The Board appreciates the understanding of the boating public, the marina operators and the public in general during this state of emergency.

The Board, in conjunction with its staff, will continue to monitor the situation and act accordingly.The Board intends to review this strategy in mid-September at its regularly scheduled monthly teleconference.

The International Joint Commission was created under the Boundary Waters Treaty of 1909 to help prevent and resolve disputes over the use of waters along the Canada-United States boundary. Its responsibilities include approving certain projects that would change water levels on the other side of the boundary, such as the international hydropower project at Massena, New York and Cornwall, Ontario. When it approves a project, the Commission’s Orders of Approval may require that flows through the project meet certain conditions to protect interests in both countries. For more information, visit the Commission’s website at www.ijc.org.

The International St. Lawrence River Board of Control was established by the International Joint Commission, mainly to ensure that outflows from Lake Ontario meet the requirements of the Commission’s Orders of Approval. For more information, visit the Board’s website at www.islrbc.org.

For Release: August 19, 2003


Reg Golding, Ottawa, Ontario (613) 998-1408

John Kangas, Chicago, Illinois (312) 353-4333