The International St. Lawrence River Board of Control (Board) reviewed conditions in the Lake Ontario - St. Lawrence River system on October 21 and decided to continue with the release of outflows specified by Plan 1958-D. Because of the current low levels on Lake St. Lawrence caused by the high outflows, the Board also authorized outflow reductions to maintain safe navigation depths in the Seaway channel at Long Sault should the level be pushed down further by wind effects common at this time of year. Also, the current low levels in the Montreal area are being exacerbated by low inflows from the Ottawa River and local tributaries, so the Board authorized outflow increases that may be needed to maintain the level on Lake St. Louis, as measured at Pointe-Claire, above 20.6 m (67.6 ft) and meet critical needs of navigation in the Port of Montreal. Similar increases were authorized to meet critical needs of hydropower interests during the fall. Any such over- or under-discharges will be limited to no more than 600 cubic metres per second (cms) (21, 200 cubic feet per second (cfs)) per day and 300 cms (10, 600 cfs) per week. Other factors considered in deciding on this strategy are as follows:

• Plan 1958-D has continued to respond well in dealing with the varying supplies of recent months. The Lake Ontario level continues to decline by a bit more than its normal rate of decline at this time of year. On October 20, the Lake level was about 7 cm (2.8 in.) above average. The level is expected to decline to the long-term average by mid November if normal amounts of precipitation and evaporation occur on the basin in the coming weeks and Plan 1958-D outflows continue to be followed.
• Last week the total supplies to Lake Ontario were above average, the first time they were above average since early September. This largely reflects the rain received over the local basin. Supplies from Lake Erie have been near-average and are expected to remain there for the next several months. Precipitation on the Lake Ontario basin and evaporation from the Lake surface will continue to be the key factors in establishing Plan outflows and the rate of decline in the Lake level over the next few weeks.
• The Board will continue to closely monitor precipitation amounts, Plan outflows and the rate of decline in the Lake and take action to avoid too large a drop in water levels in the Montreal area if there is a large reduction in the Plan outflow.
• Water levels in the Montreal area are expected to remain below average for the next month if Ottawa River and local tributary inflows remain below average.
• There are still 3.7 cm (1.5 in.) of water conserved on Lake Ontario, being held to meet critical needs of interests. There is a chance that a portion of this reserve might be needed to assist navigation in the Port of Montreal and Seaway in November and December if conditions are dry over the next several weeks.
• Risk analysis shows that the level of Lake Ontario will remain well within the range of levels specified in the International Joint Commission’s criteria for regulation of Lake Ontario for the next 8 months unless the most extreme wet or dry conditions occur. The levels should also remain well below levels thought to exacerbate shoreline erosion and well above minimum levels required for safe navigation in the Seaway.
• However, there is a significant chance that levels on the Lake will be below the ideal level for boaters by next June. There is also about a 10% chance that Lake St. Louis will reach flood levels in the spring.

There is almost a 50-50 chance that the Port of Montreal will experience at least a week of below-datum levels before the end of this year. This would improve if significant rainfall occurs in the next several weeks.

The Board, in conjunction with its staff, will continue to monitor the situation, and will meet again in about three weeks to re-assess the situation, or earlier if there is a significant change in conditions before then.

This information can also be found on the Board’s web site (see address below), where it is updated as required.

For Release: October 26, 2004

Contacts:

Reg Golding, Ottawa, Ontario (613) 998-1408 e-mail: GoldingR@dfo-mpo.gc.ca

John Kangas, Chicago, Illinois (312) 353-4333 e-mail: John.W.Kangas@usace.army.mil