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

Lake Ontario Outflow Strategy
(October 27, 2003)

The level of Lake Ontario is in its normal seasonal decline and fell approximately 7 cm (2.8 in.) during the first three weeks of October. On October 19, the Lake level was 74.62 m (244.82 ft.), which is the same as the long-term average and about 14 cm (5.5 in.) higher than last year at this time. As a result of the Board’s strategy to conserve water on the Lake in the spring and summer, for future critical needs, there are approximately 2.6 cm (1.0 in.) of water conserved on the Lake, relative to the level that would have occurred if Plan 1958-D had been followed exactly. Total supplies to the Lake Ontario basin during the first three weeks of October were below normal for this period due to lower than average supplies from Lake Erie which remains below it long-term average level. Water levels on the other upper Great Lakes also remain lower than average and lower than they were a year ago. Lake Erie is at approximately the same level as it was last year at this time.

The levels on Lake St. Louis and at the Port of Montreal have continued their rising trend which began in early October and by October 19 had risen to 12 and 33 cm (4.7 and 13.0 in.), respectively, below average.

If water supply conditions to Lake Ontario remain below average, the level of Lake Ontario will fall below average in the next few weeks and remain several centimetres below average until seasonal freeze-up. Outflows would also be below normal amounts for the remainder of the season. If supplies return to normal values, Lake Ontario would still fall below average by December.

The Board reviewed these and other conditions in the Lake Ontario-St. Lawrence River basin on October 21 and decided to maintain the same long-term strategy as was announced on October 10. The long-term strategy is, in consideration of the continued below-average levels on the upper Great Lakes and within current system constraints, to ensure that enough water is in Lake Ontario to meet future critical needs. The Board also agreed on a short-term strategy, which is to meet critical needs and, as opportunities arise, conserve additional water for future critical needs. To accomplish this, outflows will be determined by Regulation Plan 1958-D, except for the following deviations to meet critical needs or to conserve water:

  1. 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.);
  2. 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 in.) and, after a week, a change in Lake Ontario level of about 1 cm (0.4 in.)); and,
  3. Flow decreases to conserve up to 10 cm of water on Lake Ontario, at a maximum weekly under-discharge of 300 m3/s (10,600 cfs), as opportunities arise.

The Board, in conjunction with its staff, will continue to monitor the situation and act accordingly. The Board intends to review this strategy at its next scheduled Conference Call on November 12.

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

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: October 27, 2003


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

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