FINAL REPORT - International Joint Commission

FINAL REPORT
5. During the Seaway navigation season, minimize the frequency, severity and duration of flows in the
St. Lawrence River that result in channel velocities that are not safe for commercial navigation;
6. Minimize the rate of change of levels on Lake Ontario and the St. Lawrence River;
7. Adjust the annual range and timing of water level variability on Lake Ontario and the St. Lawrence
River to follow, as closely as possible, the natural water level variability that occurred before
construction of the St. Lawrence River Hydropower Project;
8. Manage water levels and flows in the Lake Ontario-St. Lawrence River system to maximize the value of
hydro-electricity generated from water flowing through the St. Lawrence River system and the amount
of dependable energy available during peak winter and summer demand periods.
How each of the candidate plans interprets and applies these objectives is described briefly in the
candidate plan descriptions later in this chapter and in more detail in the Plan Description section of
Annex 3 to this report.
To attain a full, rich and complete description of plan criteria for an amended Order, a detailed operational
guide document needs to be written for the selected plan. The steps for conversion of a selected plan to
operational status are addressed later in this report as a transition issue. Once a plan is selected and this
transition work is accomplished, it is proposed that a new “condition (i)” of a revised Order of Approval be
cast in the following terms: “the outflows from Lake Ontario through the St. Lawrence River shall be regulated
in accordance with the objectives stated herein and approved by the Commission. The inter-relationships
and balance among these objectives are expressed in the attached operation guide for the approved
regulation plan entitled Plan 2006.”
Regulation Plan Descriptions
Plan Simulations
Alternative regulation plans were developed by plan formulators, as discussed in the previous chapter,
and assessed using the historical supplies from 1900 to 2000, along with selected centuries from the
stochastic supplies that included the driest century most severe Lake Ontario supply drought (S1); the
wettest century which also had the largest range from wet to dry supplies (S2); a century that was very
similar to the historical sequence (S3); and a century with the longest drought (S4). In addition, four
supply sequences representing potential changed climate conditions that could occur roughly fifty years
hence were analyzed. These four sequences represent very small samples of four possible climate change
scenarios, and were used to ensure that the candidate plans would still function adequately if the climate
transitioned in any of these ways. The results from the above-mentioned supply sequences are presented
under the Sensitivity Analyses section of this report. Each of the candidate plans was also tested with the
complete, 49,995-year stochastically generated sequence3.
The plans were assessed by first computing the outflows from Lake Ontario that would be specified for a
given 101-year series of water supplies to Lake Ontario and other hydrologic input data. These Lake
Ontario outflows and hydrologic data were then used to calculate the levels of Lake Ontario and levels and
flows at key points in the St. Lawrence River. These levels and flows were then used within the various
components of the Shared Vision Model to calculate:
3 The water supply sequences were “time series data” used in a sequence by the models. The new rules were applied over and
over again, in dry years and wet years, but the idea was to sample many examples of what the near future might be, not to
move forward to a futuristic time.
30 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows