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

Lake Ontario Outflow Strategy
(April 14, 2003)

The dry spell on the Great Lakes basin continues. While Lake Superior had above average supplies of water in March, all of the other Great Lakes had below average water supplies. Lake Ontario water supplies have now been below average for the past nine consecutive months. Montreal Harbour levels continued to set new record lows in March. The spring snowmelt runoff from the southern portion of the Ottawa River has passed. During this spring freshet the Board was able to reduce flows below what the regulation plan specified. Last fall, flows had been greater than what the regulation plan had specified such that the Lake Ontario water level had been reduced by 4.1 cm (1.6 inches) compared to what it would have been had the regulation plan been strictly followed. The recent flow reductions have restored the Lake Ontario level to 1.1 cm (0.4 inch) below the regulation plan level.

Water levels of all the Great Lakes are below their respective April averages and all are lower than one year ago. On April 7, Lake Ontario was at elevation 74.68 m (245.01 feet), which was 20 cm (7.9 inches) below the April average, and 22 cm (8.7 inches) below the level of one year ago. The lake has risen 39 cm (15 inches) in the past month. The water levels in Lac St. Louis and Montreal Harbour on April 7 were about 20.59 m (67.6 feet) and 5.81 m (19.06 feet), respectively. These were 111 cm (44 inches) and 172 cm (68 inches) below their respective April averages.

The Board discussed these and other conditions in its meeting on April 7 and updated the outflow regulation strategy announced on March 12. In consideration of the continued low supplies throughout the Great Lakes, the long-term strategy is to conserve water on Lake Ontario, as opportunities arise, for critical needs later in the year and within current operational constraints. Through the second week of May, 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 Lac 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). Under-discharges of greater than 300 m3/s (10,600 cfs) may occur to prevent the level of Lac St- Louis from rising above its 22.10 m (72.51 ft) flood alert level.

b) Flow increases to maintain Lac 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), the minimums for full draft Seaway navigation.

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.

The Board intends to review this strategy in May at its regularly scheduled monthly teleconference, or before if conditions require. The Board continues to closely monitor the conditions on the 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: April 14, 2003


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

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