FINAL REPORT - International Joint Commission

• Hydropower energy and value;
• Commercial navigation shipping costs, including additional costs due to light loading, delays caused
by steep gradients in the River, and delays incurred by ships waiting for enough depth;
• Municipal water plant costs for treating water during droughts and for improving infrastructure to
allow the intake of water during droughts;
• Recreational boating impacts, using functions that related the value of the boating experience and the
physical ability to boat during low and high water conditions;
• Flood damages;
• Damages due to erosion of unprotected properties on Lake Ontario;
• Damages to shore protection along Lake Ontario and the upper and lower St Lawrence River;
• The 32 key environmental performance indicators.
FINAL REPORT
Baseline Plan
Plan 1958-D with Simulated Deviations (1958-DD)
Plan 1958-D “with deviations” was selected by the Study Board as the baseline for comparison purposes.
Economic results are displayed as the net difference between the impact of an alternative plan and the
impact of Plan 1958-D with simulated deviations (termed 1958-DD) in such a way that if a plan can
improve things relative to 1958-DD, it produces a positive economic benefit, and if the outcome is worse
than under 1958-DD, it produces a negative economic benefit. Environmental results are displayed as
ratios of performance indicator scores under the alternative plan to performance indicator scores for Plan
1958-DD, so ratios greater than one indicate an improvement over 1958-DD and less than one a
deterioration relative to 1958-DD.
Lake Ontario releases are now made using Plan 1958-D, but with deviations made under the direction of
the International St. Lawrence River Board of Control. These deviations from the specified Plan 1958-D
outflow have been made under different authorities granted to the Control Board by the International Joint
Commission. Deviations are also allowed for conditions that Plan 1958-D is not flexible enough to
address, such as management of ice in the River, which happens at different times in different ways each
year. The “Criterion (k)” deviations refer to the criterion in the Orders of Approval that permits the Control
Board to ask the Commission for deviations from the Plan 1958-D specified flow when water supplies are
more extreme than the 1860 to 1954 supplies that Plan 1958-D was designed to manage.
A record of these deviations from Plan 1958-D exists for the period since regulation began under Plan
1958-D in 1963. Although needs have evolved since then, and the membership and perspective of the
Control Board has changed, one might assume that similar deviations from Plan 1958-D would again be
made by the Control Board given the same circumstances, both in terms of hydrology and user needs.
Based on that assumption release rules were programmed that attempt to capture the logic of the Control
Board, and those release rules were labelled “Plan 1958-DD.” The resulting levels and flows from Plan
1958-DD can only be approximations of the actual historical flow decisions made by the Control Board.
The Control Board logic has evolved over the decades and Plan 1958-DD used the logic of recent Boards
with emphasis on the last decade. So the baseline plan is not meant to replicate the historical water levels
and flows, but is meant to be a best estimate of how the Control Board would regulate levels in the near
future. The degree to which Plan 1958-DD captures the current operating regime was tested by comparing
the simulated and recorded levels and flow for the 1960 to 2001 period, again with emphasis on the last
decade, since this was assumed to be representative of the present regime. Results of that testing and a
full description of Plan 1958-DD are available in the Plan Descriptions section of Annex 3 to this report.
Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows
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