The International St. Lawrence River Board of Control (Board) reviewed conditions in the Lake Ontario - St. Lawrence River system on April 11 and decided to closely follow the outflows prescribed by regulation Plan 1958-D for the next month. The Board took note of the conditions since it last met in March. Precipitation in March was well below average and, in spite of the heavy rainfall in early April and melting of the snowpack, the risk of low water levels has increased, while the risk of high water levels has decreased. Plan 1958-D continues to respond to the above average Lake Ontario levels by specifying increased outflows. There is still a risk of flooding downstream over the next several weeks. Considering this risk of downstream flooding, the diminished risk of high levels on Lake Ontario and the impacts on other interests of flows greater than specified by Plan 1958-D, the Board decided to retain the water conserved on Lake Ontario until at least its next meeting.

The Board’s intent last month of reducing the amount of water conserved on Lake Ontario (relative to Plan-prescribed outflows) was partially accomplished by increasing outflows above those called for by the Plan for four days. The outflows were then reduced for two days in response to an ice jam downstream, and then for another three days to reduce flooding in Montreal.

Other factors considered in deciding on this strategy are as follows:

• Plan 1958-D has continued to respond well in dealing with the above-average water supplies of recent months. The Lake Ontario level has risen more than normal since the beginning of January. On April 10^th, the Lake level was at 75.03 m (246.16 ft). This level is 20 cm (7.9 in.) above average. Under average weather conditions, the level is likely to remain fairly constant. The long-range water levels forecast indicates the Lake would be below average at the end of June if average weather conditions occur.
• Last month the total supplies to Lake Ontario were below average. The rise in levels earlier this month largely reflects the heavy precipitation received the first few days of the month and the completion of the snowmelt. It also partially reflects the outflow reductions required to alleviate downstream conditions.
• 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 ten months unless extreme wet or dry conditions occur. The risk of Lake Ontario exceeding the upper limit during 2005 is now estimated at 2%; last month the risk was estimated at 8%.
• Lake St. Louis reached 22.21 m (72.9 feet) earlier this month. It would have risen to about 22.6 m (74.1 feet) if the Board had not reduced Lake Ontario’s outflows. (Flood level is 22.33 m.) The first freshet (of the lower portion) of the Ottawa River is receding. The second freshet (of the upper portion) of the Ottawa River basin is expected over the next several weeks. Lake Ontario outflows will be reduced again if needed to avoid flooding.
• Once the freshet recedes, water levels in the Montreal area are expected to remain below average, but above Chart Datum, over the next six months. There is about a 60% chance that the Port of Montreal will experience below-datum levels at some point later in 2005.

The Board, in conjunction with its staff, will continue to monitor the situation, and will meet again in about four weeks to reassess 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.

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 Commission’s Orders of Approval may require that flows through the project meet certain conditions to protect interests in both countries. For more information, visit the Commission’s 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 Commission’s Orders of Approval. For more information, visit the Board’s website at www.islrbc.org.

For Release: April 18, 2005

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