FINAL REPORT - International Joint Commission

The timing of water availability within the year is important, in different ways for different purposes. The
level of commercial navigation and recreational boating activity drops considerably in the winter. The value
of energy generated in the summer during peak energy demand periods can be more than twelve times the
value in the spring.
FINAL REPORT
Higher releases reduce the level of Lake St. Lawrence, which is immediately upstream of the hydropower
dam. If the releases are too high, the levels can be so low that they are hazardous to navigation and could
result in ship groundings. In addition, high flows can produce cross-currents that make it difficult to control
vessels. For hydropower, more electricity can be generated when there is a greater volume of water
passing through the turbines; however, the consequent lowering of Lake St. Lawrence decreases the head
on the hydropower stations and reduces the amount of electricity generated for each cubic meter of water.
The Orders of Approval require that riparian interests downstream receive no less protection from flooding
than would have occurred under pre-project conditions. Regulation of Lake Ontario outflows has actually
reduced spring flooding in the Montreal area, while still reducing flooding on Lake Ontario. Montreal is
threatened by flooding since it is located at the confluence of the Ottawa and St. Lawrence rivers. The spring
runoff from the Ottawa River Basin is largely uncontrolled and can be very significant. Timely adjustment
of the Lake Ontario outflow has repeatedly helped avoid serious flooding around Lake St. Louis in the
Montreal area during Ottawa River floods. Lake Ontario outflow reductions are typically offset by higher
flows prior to the Ottawa River flood, or shortly following it.
The Basis for Decisions in the Study
The Commission’s directive calls for the Study Board to undertake studies required to provide the Commission
with the information it needs to evaluate criteria and options for regulating water levels and flows in order
to benefit affected interests that rely on the resources of the Lake Ontario-St. Lawrence River system as a
whole in a manner that conforms to the requirements of the Boundary Waters Treaty. To meet this
mandate, the Board adopted a vision and goal and developed the following guidelines for its activities as
the foundation for providing advice to the Commission.
Vision
To contribute to the economic, environmental and social sustainability of the Lake Ontario and St. Lawrence
River System.
Goal
To identify flow regulation plans and criteria that best serve the range of affected interests, are widely
accepted by all interests, and address climatic conditions in the basin.
Guidelines
1. Criteria and regulation plans will contribute to the ecological integrity of the Lake Ontario-St. Lawrence
River ecosystem.
This guideline will be measured by the positive or negative movement in environmental Performance
Indicators (PI) to the degree those PIs are significant, certain and sensitive to changes in levels and
flow as outlined below.
a. Significance - the PI must show some key importance to the ecosystem and region
b. Certainty - there must be confidence in the results
c. Sensitivity - the PI must be affected by changes in levels and flows
Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows
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