International Lake Ontario - St. Lawrence River Board

Frequently Asked Questions


The purpose of these FAQs is to provide stakeholders along Lake Ontario and the St. Lawrence River with information on how the International St. Lawrence River Board of Control manages the St. Lawrence River flows under the direction of the International Joint Commission’s Orders of Approval, while also ensuring the most equitable distribution of benefits and impacts for all citizens living and working along this magnificent and spectacular watercourse.

These FAQs represent questions that have commonly been asked or address areas where we feel additional information would be useful for the public. We would sincerely appreciate your comments and suggestions in order to provide the best information and perspective for you, the citizens of the Lake Ontario and St. Lawrence River System and stakeholders, regarding management of its waters for all interests.

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Please send your comments, suggestions, and questions to the Board’s secretaries: Contact Us.

This FAQ Site is organized with the following sections:  

 1.1 Why do levels and flows fluctuate in the Lake Ontario-St. Lawrence River system? 
 1.2 Water from Lake Erie, precipitation, and wind are the major natural forces affecting Lake Ontario. How significant are these forces, and why?
 1.3 What influence does isostatic rebound have on what is happening to water levels and water access around the Lake Ontario shoreline?
 1.4 What influence does climate change, increased evaporation and other factors have on what is happening to water levels and water access around the Lake Ontario shoreline?
 1.5 What are the overall actual and potential impacts of these changing conditions on the north shore of Lake Ontario?
 1.6 How does ice affect lake evaporation and Lake Ontario water levels?



2.1 What was the purpose of the hydropower and seaway project?
2.2 What caused changes in the levels of Lake Ontario before regulation, and what is causing changes after regulation?
2.3 What was the “natural” annual cycle of levels in Lake Ontario before regulation in comparison with after regulation?
2.4 Why were levels on Lake Ontario lower prior to regulation than they have been since regulation?
2.5 What has caused changes in levels of the St. Lawrence River since regulation?
2.6 What were the “natural” levels in the St. Lawrence River downstream of Cornwall/Massena before regulation?
2.7 How is the long-term, lake-wide average level on Lake Ontario computed?
2.8 How does the Plan-specified level differ from the actual level on Lake Ontario?
2.9 Why can’t the Lake Ontario level be kept at the average level all year round?
2.10 What actions does the ISLRBC take to manage ice conditions in the St. Lawrence River during the winter?
2.11 Why is Lake St. Lawrence low when flows are high? What are the benefits and/or liabilities of such a situation?
2.12 Why are water levels so variable on the St. Lawrence to the west of Moses-Saunders Dam and so low the winter of 2015? Don’t these low levels harm fish?
2.13 How does regulation of Lake Ontario mitigate spring flooding conditions in the Montréal area?


3.1 Boundary Waters Treaty
  3.1.1 What is the Boundary Waters Treaty?
  3.1.2 What are the principal provisions of the Boundary Waters Treaty regarding projects such as dams?
  3.1.3 Does the Boundary Waters Treaty give precedence to some uses over others?
3.2 The International Joint Commission (IJC)
  3.2.1 What is the IJC?
  3.2.2 How does the IJC work?
  3.2.3 What are the Orders of Approval?
  3.2.4 What are the principal provisions of the Orders of Approval for Lake Ontario/St. Lawrence River?
  3.2.5 Are Orders of Approval ever updated?
  3.2.6 How does the IJC engage the public?
3.3 International St. Lawrence River Board of Control
  3.3.1 What is the ISLRBC?
  3.3.2 Who is on the ISLRBC?
  3.3.3 How are members of the ISLRBC appointed?
  3.3.4 Does the ISLRBC take formal votes on its decisions?
  3.3.5 What is done to ensure that the public has input into ISLRBC decisions?
  3.3.6 Are records of ISLRBC decisions accessible to the public?
  3.3.7 How does the Board increase public awareness of water and weather conditions?
3.4 Operators of the Dam
  3.4.1 Who actually operates the dam at Cornwall, Ontario and Massena, New York?
  3.4.2 What is the Operations Advisory Group (OAG)?


 4.1 What does the ISLRBC regulate?
 4.2 How does the ISLRBC go about regulation?
 4.3 Who are the Regulation Representatives and what are their duties?
 4.4 What are the criteria that the Board uses in making management (regulation) decisions?
 4.5 What other regulations and standards does the ISLRBC use in making its decisions?
 4.6 What authority does the ISLRBC have to consider individual interests when setting Lake Ontario outflows?
 4.7 What actions do the IJC and ISLRBC take to react to low water supplies and avert extreme low water levels in Lake Ontario or the St. Lawrence River?
 4.8 Can water be stored on Lake Ontario to provide a buffer against low water conditions in the Thousand Islands and/or Montréal?
 4.9 Are there ways to address low water problems other than through regulating water levels?
4.10 Should low water conditions continue for a number of years, what are the implications to the Board's approach to controlling water levels and to water users above and below the Moses-Saunders Dam?
4.11 Should the Board have a contingency plan in place if “drought-like” water supply conditions continue, even though forecasted weather conditions may not predict drought-like conditions?
4.12 If a multi-year trend to lower Lake Ontario water levels emerges, will the Board be able to maintain sufficiently high water levels above and below the Dam to stay above the lowest level needed to maintain Seaway operations?
4.13 What adaptive measures should water users and property owners be taking above and below the Dam to protect against adverse impacts, and will the Board be taking actions to encourage such measures to be implemented?
4.14 Doesn’t knowing the snow pack provide a reliable indicator of the water supplies for the spring and summer season?
4.15 Can Lake Ontario water levels be reduced in the fall of each year to provide a buffer against high water supplies the next spring?
4.16 What is criterion (k) and what triggers it during high or low water conditions?
4.17 What is criterion (h)?
4.18 What is criterion (i)?
4.19 Why doesn't the Commission use criterion (i) as the upper limit for water level regulation on Lake Ontario?


5.1  General
  5.1.1 What is the value of high water? Who is impacted?
  5.1.2 What is the value of low water? Who is impacted?
  5.1.3 At what Lake Ontario level(s) do adverse impacts from low or high water occur?
  5.1.4 What can shoreline communities do, if anything, to assist the Board?
  5.1.5 What have been the impacts of regulation on Lake St. Lawrence compared to pre-project conditions?
  5.1.6 What water level information is available?
5.2 Domestic Water Supplies and Sanitary Uses
  5.2.1 How can high or low Lake Ontario water levels affect domestic and sanitary uses?
5.3 Commercial Navigation
  5.3.1 How can the regulation of Lake Ontario outflows impact commercial navigation?
  5.3.2 Are navigation interests impacted by Lake Ontario water levels?
  5.3.3 Can the navigation season between Lake Ontario and Montréal close earlier so more water can be let out of Lake Ontario?
5.4 Hydropower
  5.4.1 Do hydropower interests benefit from high Lake Ontario outflows?
  5.4.2 When the Board increases outflows from Lake Ontario is the water spilt or is it still used to generate electricity?
5.5 Environment
  5.5.1 What authority does the ISLRBC have to consider the environment when setting Lake Ontario outflows?
  5.5.2 Has regulation had an adverse impact on wetlands due to the reduction of the occurrence of extreme high and low water levels on Lake Ontario?
  5.5.3 How has regulation impacted the environment upstream of the project at Massena and Cornwall?
  5.5.4 How has regulation impacted the environment downstream of the project?
5.6 Riparian and Shoreline Property Owners
  5.6.1 What factors affect shoreline flooding and erosion?
  5.6.2 What have been the benefits to St. Lawrence River riparian property owners as a result of Lake Ontario regulation?
  5.6.3 Are there ways to address flooding and erosion problems other than through regulating water levels?
  5.6.4 What can I, as a landowner, do to protect myself from high water damages to my property? What can the Board do to help me?
5.7 Recreational Boating
  5.7.1 Other than water level regulation, are there any actions that could benefit recreational boaters?