March 17, 1997
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
in the international portion of the river was essentially complete by January 31, 1997. A stable
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
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
from Lake Erie, precipitation on the Lake Ontario basin minus evaporation from the surface of
Lake Ontario, are summarized below:
||7,490 cms (264,000 cfs)
||6,080 cms (215,000 cfs)
||7,460 cms (263,000 cfs)
||6,060 cms (214,000 cfs)
||8,160 cms (288,000 cfs)
||6,510 cms (230,000 cfs)
||9,000 cms (318,000 cfs)
||6,720 cms (237,000 cfs)
||8,280 cms (292,000 cfs)
||6,590 cms (233,000 cfs)
||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
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
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