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

Lake Ontario Outflow Strategy
(October 15, 2002)

Precipitation on the Great Lakes basin has generally been below average in July, August and September. In particular, precipitation on Lakes Erie and Ontario basins, in September, was 103 % and 87 % of average, respectively , a slight improvement over the drier summer months of July and August.

On 7 October, Lake Ontario was at elevation 74.54 m (244.55 feet), which was 11 cm (4.3 inches) below the average for this time of the year, but slightly above the level of one year ago. The water levels in Lake St. Louis and Montreal Harbour were 20.65 m (67.75 feet) and 5.31 m (17.42 feet), respectively. These were 51 cm (20.1 inches) and 103 cm (40.5 inches) below average and 1 cm (0.4 inch) and 23 cm (9.1 inches) above their level last year at this time.

The Board met on 7 October and, after reviewing the hydrologic conditions in the Lake Ontario-St. Lawrence system, decided on the following outflow regulation strategy:

Outflows will be generally as determined by Plan 1958D. 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:

  • Ensure Montreal Harbour is at least chart datum when required by deep draft ship arrivals and departures, when possible within the above limitations.
  • Maintain at least 20.6 m (67.58 feet) on Lake St. Louis.
  • Ensure outflow increases to meet critical hydropower needs.

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 Plan 1958-D. The strategy also allows for less than Plan 1958-D specified outflows if downstream conditions are favourable to do so. The strategy will be reviewed should accumulated over-discharges reach 5 cm below Plan level, but in any event no later than early December.

The Board continues to closely monitor the conditions on 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: October 15, 2002


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

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