FINAL REPORT - International Joint Commission

FINAL REPORT
The programmed Plan 1958-DD was run through all of the time series sequences to provide the baseline
against which all plans would be compared. To allow this comparison, all economic damages related to
1958-DD were set to equal zero such that any increase in damage was considered a negative benefit and
any decrease in damages was considered a positive benefit. While all damages were set to zero for
comparative purposes, this does not mean there are zero damages under Plan 1958-DD. For example,
shoreline erosion damages are an ongoing phenomenon and occur with every regulation plan. The issue
for plan evaluation is whether an alternative regulation plan will make things better or worse than Plan
1958-DD. The absolute economic damages for Plan 1958-DD can be found in Annex 3.
Since the environmental performance indicators were reported as ratios, there are no absolute damages
available. However, it has been reported that the current Lake Ontario regulation plan has resulted in a loss
of about 1,000 hectares (2,500 acres) of meadow marsh and 700 hectares (1,750 acres) of emergentfloating
vegetation, with an equivalent increase of 1,700 hectares (4,250 acres) in cattail-dominated
emergent marsh (Wilcox and Ingram, 2005).
The dynamics of regulation are very complex and have been fine-tuned for those interests that were
considered to be most important 50 years ago. However, the present regulation has been detrimental to
the Lake Ontario and St. Lawrence River (upper and lower) ecosystem, while riparian interests, commercial
navigation and hydropower have generally benefited during the past four decades of operation.
Reference, Interest-Specific and Natural Flow Plans
Reference Plans
While the key focus of the study is to design new regulation plans, it is also incumbent upon the Study
Board to use the Study’s performance indicators to comparatively assess plans recommended in the past
to the IJC, and to determine the impacts of adhering strictly to the written 1958-D regulation plan without
deviations. The research and analytical tools developed within the Shared Vision Model for this Study
allow, for the first time, a full, quantified assessment of the impacts of these alternative plans relative to
Plan 1958-D with simulated deviations (1958-DD). The two plans modeled as reference plans were Plan
1958-D without deviations and Plan 1998.
As described in the introduction, Plan 1958-D is composed of three basic elements:
• Two rule curves (the second for drought that is used during a portion of the year, but only when Lake
Ontario is below 74.47 m (244.33 feet)) that assign a specific release to every level of Lake Ontario;
• Adjustments to the rule curves to change the release based on the time of year and the recent trend in
water supplies;
• Limits to constrain releases within maximum and minimum levels, to restrict the rate of change from
week-to-week, and to reflect winter flow reductions designed to avoid flooding related to ice.
When evaluated based on supplies in the last half of the twentieth century, which was marked by both
wetter and dryer periods, Plan 1958-D would allow Lake Ontario to rise higher than it would have without
regulation, probably in violation of the Orders of Approval for the project.
Plan 1998 was developed by the International St. Lawrence River Board of Control following the 1993
Levels Reference Study. This Plan was developed within the scope of the existing 1956 Orders of Approval
criteria. It is a modification of Plan 1958-D, and uses the same three-element structure. The limits of Plan
1958-D were modified so that the objectives of the Orders of Approval would be better met under the water
supply conditions encountered since 1958-D went into effect. Plan 1998 also uses an ice indicator time
series to allow more realistic simulation of the variability of ice formation timing from year to year. The plan
was recommended to the International Joint Commission in June 1997. Public responses to the new
32 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows