Outflow Strategy
. .

Copyrights : International St. Lawrence River Board of Control

Lake Ontario Outflow Strategy
(December 16, 2002)

Precipitation and water supplies were well below average in November for the upper Great Lakes. Although Lake Ontario basin precipitation and local supplies were near average for the last two months, total supplies to the lake were below average due to low outflows from Lake Erie. Montreal Harbour levels set new record minimums for October and November and were below chart datum. November daily levels at Pointe Claire on Lake St. Louis ranged between 20.60 m and 20.86 m.

The water levels of all the Great Lakes were below their respective November averages and lower than one year ago. On 10 December, Lake Ontario was at elevation 74.30 m (243.77 feet), which was 23 cm (9 inches) below the average for this time of the year, and 20 cm (7.9 inches) below the level of one year ago. The water levels in Lake St. Louis and Montreal Harbour were about 20.66 m (67.78 feet) and 5.30 m (17.39 feet), respectively. These were 60 cm (24 inches) and 129 cm (51 inches) below average and 28 cm (11inches) and 64 cm (25 inches) below their levels last year at this time.

The Board discussed these and other conditions in a teleconference on 11 December and decided to continue the outflow regulation strategy announced on November 15 with appropriate considerations in the light of anticipated winter operations. That is:

Outflows will be generally as determined by Regulation Plan 1958-D, except for the following deviations:

a. Provided that the ice conditions in the St. Lawrence River permit, a maximum weekly over-discharge of 300 m3/s (10,600 cfs) and no more than 600 m3/s/day (21,200 cfs/day) above Plan will be released as required for the following purposes:

  • Raise Montreal Harbour levels when required by deep draft ship arrivals and departures, within the above limitations.
  • Maintain at least 20.6 m (67.6 feet) on Lake St. Louis until December 15th and 20.52 m (67.3 feet) thereafter until the Seaway closes in late December; and once the Seaway has closed, a minimum of 20.45 m (67.1 feet).
  • Meet critical hydropower needs within the above limitations.

The outflow increases for the purposes mentioned above may use the equivalent of a maximum of 8 cm of water from Lake Ontario relative to Regulation Plan 1958-D. As of December 9, the accumulated over-discharges were at 3.7 cm (1.4 inches).

b. The strategy includes opportunities for under-discharges, if conditions are favorable to do so, in order to restore the water taken off Lake Ontario relative to the Regulation Plan. Such opportunities might arise if outflows are reduced below Plan specified amounts to assist in ice formation and management.

The strategy will be reviewed should accumulated over-discharges reach 6 cm (2.4 in.) below Plan level. The Board intends to review this strategy in January, at its regularly scheduled monthly meeting, or before if conditions require.

The Board continues to closely monitor the conditions on the Lake Ontario-St. Lawrence River System and will intervene 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 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 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 Commissionís Orders of Approval. For more information, visit the Boardís website at www.islrbc.org.

For Release: December 16, 2002


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

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


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

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