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

Lake Ontario Outflow Strategy
(November 15, 2002)

Precipitation was generally near average in October for the Lakes Ontario, Michigan and Huron basins. Lake Erieís basin received about 69% of its average October precipitation. The net total water supplies to these basins (the net effect of over-lake precipitation, inflow from the upper Great Lake, basin runoff, and evaporation from the lake) was below average in October for all of these lakes. Last month, the water supplies to Lakes Michigan-Huron were close to a record minimum. As a result, all of these lakes experienced larger than average drops in water levels in October. Water supply to Lake Superior last month was slightly above average. Downstream, Montreal Harbour levels set a new record low for the month of October for the period of record 1967 to the present.

On 12 November, Lake Ontario was at elevation 74.38 m (244.03 feet), which was 17 cm (7 inches) below the average for this time of the year, and 9 cm (4 inches) below the level of one year ago. The water levels in Lake St. Louis and Montreal Harbour were about 20.70 m (67.91 feet) and 5.43 m (17.81 feet), respectively. These were 52 cm (20 inches) and 110 cm (43 inches) below average and 11 cm (4 inches) and 33 cm (13 inches) below their levels last year at this time.

The Board discussed these and other conditions in a teleconference on 13 November and decided to continue the outflow regulation strategy announced on October 15. That is:

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. As of November 8, the accumulated over-discharges were at 2.8 cm (1.1 inch), which is the amount of water taken off Lake Ontario due to actual Lake Ontario outflows up to that day more than the amounts specified by the regulation plan.

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: November 15, 2002


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

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