Outflows From Lake Ontario Set Records for February and Early March

Contact Frank Bevacqua Washington, D.C. (202) 736-9024   Fabien Lengellé Ottawa, Ontario (613) 995-0088

Outflows From Lake Ontario Set Records for February and Early March

Outflows from Lake Ontario during the month of February and first two weeks of March set new records for this time of year, according to the International Joint Commission.

Average flows in January were kept to 7,250 cubic meters per second (cms) or 256,000 cubic feet per second (cfs) by the Commission's International St. Lawrence River Board of Control to facilitate the formation of a stable ice cover on the St. Lawrence River. Formation of the ice cover in the international portion of the river was essentially complete by January 31, 1997. A stable ice cover helps to prevent underwater ice blockages that can restrict flows. This winter's ice cover has been very smooth and stable, allowing much higher flows than usual.

In early February, the Board of Control increased outflows steadily and a record outflow of 8,310 cms (293,000 cfs) was achieved for the month. Outflows during the first and second weeks of March were 8,820 cms (311,500 cfs) and 9,100 cms (321,400 cfs) respectively, which are also record outflows for this time of year.

The Commission invoked criterion (k) of its Orders of Approval for Lake Ontario-St. Lawrence River regulation on January 17, 1997 to provide all possible relief to shoreline property on Lake Ontario and the St. Lawrence River from the Thousand Islands to past Montreal. Considerable relief has been provided to the Lake Ontario shoreline under criterion (k) operations because favorable ice conditions have made greater outflows from Lake Ontario possible.

Ice conditions and imminent danger of flooding in the Montreal area are currently the only limits on flows in the St. Lawrence River. Because water supplies to Lake Ontario are expected to remain high, not all flooding on the lake or river can be prevented. However, the Board of Control is carefully monitoring conditions throughout the Lake Ontario-St. Lawrence River system in order to maintain high flows without increasing the probability of flooding.

On March 13, the level of Lake Ontario was at 75.01 meters (246.10 feet) above sea level (International Great Lakes Datum 1985). This level was 49 centimeters (1.61 feet) below what it would have been had the regulation plan been strictly followed and 67 centimeters (2.2 feet) below what it would have been had the power project never been built.

Despite the high outflows, the Commission and Board of Control caution that the potential for adverse conditions and flooding remain high this year. The total inflow from Lake Erie will remain above average for at least the rest of the year. Before peaking in spring or early summer, Lake Ontario could still rise approximately another 20-30 centimeters (eight-12 inches) with normal precipitation and up to approximately 40 centimeters (16 inches) from its present level with extremely high precipitation.

The current high water levels on Lake Ontario result from the unusually high water supplies that have been received over the past six months. Water supplies to Lake Ontario, consisting of inflow from Lake Erie, precipitation on the Lake Ontario basin minus evaporation from the surface of Lake Ontario, are summarized below:


Month Actual Supplies Average Supplies September 1996 7,490 cms (264,000 cfs) 6,080 cms (215,000 cfs) October 1996 7,460 cms (263,000 cfs) 6,060 cms (214,000 cfs) November 1996 8,160 cms (288,000 cfs) 6,510 cms (230,000 cfs) December 1996 9,000 cms (318,000 cfs) 6,720 cms (237,000 cfs) January 1997 8,280 cms (292,000 cfs) 6,590 cms (233,000 cfs) February 1997 8,190 cms (289,000 cfs) 6,660 cms (235,000 cfs)

Since September 1996, the Board of Control's strategy has been to release more water from Lake Ontario than would have been called for under the regulation plan whenever this could be done without adversely affecting other interests.

The present outflow from lake Ontario is 9,200 cms (325,000 cfs), which is 1,270 cms (45,000 cfs) above the outflow called for by the regulation plan and 2,530 cms (89,000 cfs) more than the average outflow for the month of March. The approaching spring melt in the Ottawa River basin will increase the likelihood of flooding around Montreal and may constrain Lake Ontario outflows.

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 hydropower project near Cornwall, Ontario and Massena, New York. The Commission established the International St. Lawrence River Board of Control to ensure that outflows from Lake Ontario meet the requirements of the Commission's Orders. The Board also develops regulation plans and conducts special studies as requested by the Commission.