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

Lake Ontario Outflow Strategy
(December 15, 2003)

The International St. Lawrence River Board of Control (Board) has reviewed conditions in the Lake Ontario - St. Lawrence River basin and decided to revise its outflow strategy. The Board met by teleconference on December 10 to consider the impacts of the above-average precipitation experienced since its conference call of November 12. While still below average, Lake Erie’s level on December 9 was 8 cm (3.1 in) higher than last year at this time. The level of Lake Ontario was 74.69 m (244.05 ft), which is 16 cm (6.3 in) above average, and 38 cm (15.0 in) higher than last year at this time. As a result of the Board’s strategy to conserve water this Fall on the Lake for future critical needs, there are 9.1 cm (3.6 in) conserved on Lake Ontario, relative to the level that would have occurred if Plan 1958-D had been followed exactly. Lake St. Louis and Montreal Harbour are 34 cm (13.4 in) and 48 cm (18.9 in) above their long term averages and 92 cm (36 in) and 174 cm (68 in), respectively, above their levels of a year ago.

Outflows in November were reduced by 300 cms below Plan to conserve water on the lake without causing disbenefits to interests. Above average flows from the Ottawa River continued to maintain satisfactory levels at the Port of Montreal. November’s under discharges also helped the hydropower entities to attend to normal servicing of some of their units.

The Board noted that with the likely continuation of high Ottawa River and downstream tributary outflows in the next few weeks, the expected "I" limit of the Regulation Plan would cause the plan to specify greatly reduced outflows for the next three weeks. Strictly following Plan 1958-D would result in flows decreasing by about 1000 m3/s (35,300 cfs) for the week ending December 19, and further reductions to flows in the low 6000 m3/s (212,000 cfs) range the following two weeks. The "I" limit of Plan 1958-D limits Lake Ontario outflows such that the flow from Lake St Louis is no more than 7930 m3/s (280,000 cfs). This limit was incorporated into Plan 1958-D to assist the ice formation process on Lake St. Louis for a planned (but not constructed) power plant at the outlet of that lake.

The Board considered the following factors (among others) in revising its strategy:

► the above average level of Lake Ontario;

► the 9.1 cm (3.6 in) of water conserved relative to the plan;

► the potential need to reduce flows below those of Plan 1958-D during the ice formation period in the Beauharnois canal and the international section of the river, as is the customary practice;

► the likely Plan 1958-D specified outflows;

► the need to avoid large decreases in flows during the period that the "I" limit applies in order to avoid precipitous decreases in levels downstream and increases upstream on Lake St. Lawrence;

► the impact of over-discharges over the next 3 weeks on the amount of water conserved;

► the potential for conserving water during ice formation and during the spring freshet; and,

► several options for the amount of water to conserve on the lake prior to the onset of forming ice at Beauharnois and in the international section of the river.


The Board agreed to update the strategy as was announced on November 17. The long-term strategy, in consideration of the continued below-average levels on the upper Great Lakes (Superior, Michigan, and Huron) and within current system constraints, is still to ensure that enough water is in Lake Ontario to meet future critical needs. The short-term strategy is to reduce the amount of water stored over the next 3 weeks that the I Limit applies and to meet winter operations (ice formation) needs. During the ice formations period, a modest amount of water may be conserved on the lake for future critical needs. To accomplish this, the outflows specified by Plan 1958-D during the next five weeks will be modified as follows:

  1. Outflows greater than those specified by Plan 1958-D over the next 3 weeks (through January 2, 2004) will reduce the current storage from 9.1 cm to about 3 cm;
  2. Outflows over the next 3 weeks will be the lesser of 7000 m3/s (247,000 cfs) or 600 m3/s (21,200 cfs) above the ouflow specified by Plan 1958-D; and,
  3. Outflows will be adjusted as required to facilitate ice formation.

The Board, in conjunction with its staff, will continue to monitor the situation and act accordingly. This information can also be found on the Board web site (see below) and will be updated 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 Commission’s Orders of Approval may require that flows through the project meet certain conditions to protect interests in both countries. For more information, visit the Commission’s 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 Commission’s Orders of Approval. For more information, visit the Board’s website at www.islrbc.org.

For Release: December 15, 2003


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

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