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

Lake Ontario Outflow Strategy
(May 22, 2003)

Despite the recent wet spell, the water levels on all of the Great Lakes were below their levels of a year ago at mid-May. All of the Great Lakes had below average water supplies in April. For Lake Ontario, this was the tenth consecutive month with below average water supplies. Montreal Harbour levels continued to set new record lows in April. The spring snowmelt runoff from the northern portion of the Ottawa River has passed and that river is expected to slowly decline over the next several months. During the spring freshets the Board was able to reduce flows below what the regulation plan specified. The recent flow reductions have allowed the Board to restore the approximate 4 cm (1.6 inches) previously used above the regulation plan level and conserve an additional 2 cm (0.8 inch) of water on Lake Ontario. The decreased outflows have caused an increase in Lake St. Lawrence levels, resulting in the gates of Iroquois Dam being lowered into the water to suppress water levels between Iroquois and the Moses-Saunders Powerhouse.

Water levels of all the Great Lakes are below their respective May averages. On May 14, Lake Ontario was at elevation 74.93 m (245.83 feet), which was 8 cm (3.1 inches) below the May average and 29 cm (11.4 inches) below the level of one year ago. The lake has risen 20 cm (7.9 inches) in the past month. Forecasts indicate that the lake could rise another 5 to 17 cm (2.0 to 6.7 inches) for continued average to wet conditions, respectively.

The water levels in Lake St. Louis and Montreal Harbour were about 20.88 m (68.5 feet) and 6.02 m (19.75 feet), respectively. These were 74 cm (29.1 inches) and 126 cm (49.6 inches) below their respective May averages.

The Board discussed these and other conditions on its teleconference on May 14 and updated the outflow regulation strategy announced on April 14. In consideration of the continued low supplies throughout the Great Lakes, the long-term strategy is to conserve up to 8 cm (3.1 inches) of water on Lake Ontario, as opportunities arise, for critical needs later in the year and within current operational constraints.

Through the second week of June, outflows will generally be as determined by the Regulation Plan 1958-D except for the following deviations.

a) A maximum weekly under-discharge of 300 m3/s (10,600 cfs) below plan will be made to conserve water on Lake Ontario, provided that the level of Lake St. Louis is maintained above 20.6 m (67.6 ft) and the level of Lake St. Francis at Summerstown is above 46.58 m (152.82 ft).

b) Flow increases to maintain Lake St. Louis levels above 20.6 m (67.6 ft) and the level of Lake St. Francis at Summerstown above 46.58 m (152.82 ft).

c) Flow increases to meet critical hydropower needs and to raise levels at the Port of Montreal for critical navigation needs at a maximum weekly over-discharge of 300 m3/s (10,600 cfs) and no more than a maximum daily over-discharge of 600 m3/s /day (21,200 cfs/day) above plan flow. A flow change of 300 m3/s will result in a change in level at Montreal of about 10 cm (3.9 inches) and, after a week, a change in Lake Ontario level of about 1 cm (0.4 inch.).

The Board intends to review this strategy in June at its regularly scheduled monthly teleconference, or before if 4 cm (1.6 inches) of water has been used before that time. The Board, in conjunction with its staff, continually monitors the conditions on the Lake Ontario-St. Lawrence River System.

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: May 22, 2003


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

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