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

Lake Ontario Outflow Strategy
(June 28, 2002)

Heavy rains fell in the upper St. Lawrence River valley the past weeks. On 15 June 2002, the outflow from Lake Ontario was reduced to the amount specified by the regulation Plan 1958-D to help avoid flooding in the Montreal region of the St. Lawrence River. Lake St-Louis level, which is also affected by the high Ottawa River outflows, rose above the flood alert level.

The situation has improved since and Lake St-Louis level has declined below the flood alert level, although it remains 56 cm (22 in.) higher than the long-term average for this time of the year.

Lake Ontario level has also increased and is currently approximately 30 cm (11.8 in.) above long-term average and 35 cm (13.8 in.) higher than last year at the same period.

The Port of Montreal level is presently approximately 1.80 m (5.9 ft.) above Chart Datum. If precipitation remains average, as actual forecasts seem to indicate, the Port level will remain above Chart Datum throughout the season.

On 22 June 2002, following the strategy previously adopted, Lake Ontario outflow was once again set at 300 m3/s (10,600 cfs) greater than called for by the Plan. This measure, by lowering the Lake level, will reduce the risk of damages to adjacent properties.

On 25 June 2002, the Board modified its strategy as follows to account for the present situation:

  • The outflow from Lake Ontario will continue to be 300 m3/s (10,600 cfs) greater than the amount specified by the regulation Plan 1958-D until Lake Ontario has peaked.
  • Then the outflow will be adjusted to 100 m3/s (3,530 cfs) greater than called for by Plan 1958-D until all the reserved water is released from Lake Ontario. The reserve, which is the net result of all previous outflow deviations from the regulation plan, is approximately 4 cm (1.6 in.), at present.
  • The strategy continues to allow for flow reductions in case of risk of flooding in the Montreal area and flow increases for critical needs of downstream navigation, power generation and supply to domestic water intakes.

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: June 28, 2002


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

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