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

Lake Ontario Outflow Strategy
(September 16, 2003)

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 on September 10 was 3 cm (1.2 in.) higher than in 2002. The level of Lake Ontario fell by 15 cm (5.9 in.) during August, which is similar to its normal August decline of 14 cm (5.5 in.). Approximately 1.5 cm (0.6 in.) of that decline was due to higher outflows to assist in the recovery from the massive power blackout that occurred that month. On September 9, the Lake Ontario level was 74.78 m (245.34 ft.), 1 cm

(0.4 in.) above its average for this time of year. Lake St. Louis and Port of Montreal levels have decreased since August, and on September 9, were 22 and 51 cm (8.7 and 20.1 in.) below average, respectively. As a result of the Boardís actions this spring and summer, there are approximately 2.6 cm (1.0 in.) of water conserved on Lake Ontario relative to the level which would have occurred if Plan 1958-D had been followed exactly.

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

The Board reviewed these and other conditions on September 10, 2003 and agreed to maintain the same strategy as was announced on August 19. The long-term strategy, in consideration of the continued below average levels on the upper Great Lakes and within current system constraints, is to ensure that enough water remains in Lake Ontario to meet critical needs later in the year. The short-term strategy is to retain as much as possible of the water already conserved on Lake Ontario. To accomplish this, outflows will generally be as determined by Regulation Plan 1958-D through the third week of September, except for the following deviations:

  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 inches) and, after a week, a change in Lake Ontario level of about 1 cm (0.4 inch).

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 scheduled meeting in the third week of September.

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 Commissionís Orders of Approval may require that flows through the project meet certain conditions to protect interests in both countries. For more information, visit the Commissionís web site 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 Commissionís Orders of Approval. For more information, visit the Boardís web site at www.islrbc.org.

For Release: 16 September 2003


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

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