For Release: May 16, 1997
St. Lawrence River Conditions Limit Lake Ontario Outflows
High Lake Ontario outflows continue, but have not been as high as the record flows set in
February and March this year because of near-flood conditions on the St. Lawrence River around
Higher water levels around Montreal have resulted from the spring melt in the Ottawa River
basin, which began in early April. The Ottawa River empties into the St. Lawrence River near
Outflows from Lake Ontario are currently limited to avoid increasing water levels in the Lake St.
Louis and Montreal Harbor portions of the St. Lawrence River -- which are above the flood alert
level, but below flood stage -- and the level of the Lake St. Pierre portion, which is above flood
Lake Ontario outflows have been increased for brief periods when conditions around Montreal
have improved, but were reduced when levels again began to approach flood stage. The
International St. Lawrence River Board of Control is monitoring conditions on Lake Ontario and
the St. Lawrence River and is releasing the maximum outflow from Lake Ontario without
contributing to downstream flooding.
The gates at Iroquois Dam were also partially closed earlier this month to suppress the high water
levels on Lake St. Lawrence, the portion of the St. Lawrence River above the international
hydropower project at Cornwall, Ontario and Massena, New York. The gates have since been
opened to the full position because recent flow increases through the project and diminishing
westerly winds have eliminated the threat of extreme high levels on Lake St. Lawrence.
The International Joint Commission invoked criterion (k) of its Orders of Approval for Lake
Ontario-St. Lawrence River regulation on January 17, 1997 when water supplies to the lake
exceeded thresholds established in the Orders. Under criterion (k), flows are set to provide all
possible relief to the shoreline owners on Lake Ontario and the St. Lawrence River. Criterion (k)
remains in effect.
Outflows from Lake Ontario were steadily increased after January 31, 1997, when formation of a
stable ice cover on the St. Lawrence River was nearing completion. A stable ice cover helps to
prevent underwater ice blockages that can restrict flows. No significant ice jams occurred and
record Lake Ontario outflows were set for the months of February and March.
To date, the spring runoff from the Ottawa River neither has been rapid nor has it contributed to
major flooding this year. The flow of the Ottawa River into the St. Lawrence River near Montreal
appears to have peaked on May 7, however, the subsequent decline in the flow of the Ottawa
river has been slow. A decline in the Ottawa River flow is expected to bring some improvements
to lake St. Louis, thus allowing increases in the Lake Ontario outflows.
Lake Ontario is currently at 75.29 metres (247.01 feet) above sea level (International Great Lakes
Datum 1985). Emergency actions taken by the International Joint Commission and International
St. Lawrence River Board of Control since September 1996 have lowered Lake Ontario by 53
centimetres (21 inches) compared to strict application of the Lake Ontario regulation plan. The
lake is currently 65 centimetres (26 inches) below where it would be now if the hydropower and
navigation project had never been built.
The following is a summary of weekly Lake Ontario outflows for 1997.
*Outflows were reduced to assist in ice formation
**Outflows were lowered due to Ottawa Freshet
||Outflow (cubic metres/second)
||Outflow (cubic feet per second)
|January 3, 1997
|January 10, 1997
|January 17, 1997
|January 24, 1997
|January 31, 1997
|February 7, 1997
|February 14, 1997
|February 21, 1997
|February 28, 1997
|March 7, 1997
|March 14, 1997
|March 21, 1997
|March 28, 1997
|April 4, 1997
|April 11, 1997
|April 18, 1997
|April 25, 1997
|May 2, 1997
|May 9, 1997
|May 16, 1997