FINAL REPORT - International Joint Commission

FINAL REPORT
Municipal and Industrial Water Uses
Validation
The surveys of water intake and outflow elevations were carefully reviewed by stakeholders and experts in
and outside the Study. Findings on Montreal’s water system were discussed with the mayors of the region
and they agreed to address the vulnerability of that system to very rare low levels.
Sensitivity Analysis
None.
Further Modifications of Plans
Each of the candidate plans represents certain trade-offs among interests. Unfortunately, no plan can create
positive benefits for all interests and regions at all times. Each plan makes the trade-offs a little differently,
and every time a plan is adjusted or modified even slightly the results can change. The International Joint
Commission may still wish to modify these balances. Near the end of the Study, one attempt at adjusting
Plan B + was pursued to try to improve coastal benefits while maintaining environmental benefits. This
modification began with Plan B + and applied a more conservative forecast in the fall, increasing outflows
at that time of year, when levels were fairly high, to ensure that winter levels never rose excessively to
threaten spring flooding. This plan, which was termed Plan G, showed some promise. It improved coastal
performance without harming the environmental scores, but did increase recreational boating damages
because of lower summer and fall levels. Modification of these plans remains an option for the
International Joint Commission.
Unexpected Conditions and Plan Flow Deviations
The 1952 IJC Order of Approval as amended in 1956 permits deviations from or changes in plan flows
under Criterion (k) in response to hydrologic conditions outside the range upon which the plan was
developed and with specific Commission approval. In addition, through its approval of the Operational
Guidelines for Plan 1958-A in 1959 and subsequent Operational Guidelines for Plan 1958-C (1962) and
1958-D (1963), the Commission recognized the need for deviations from the plan flows in response to
varying ice conditions in the River and to emergency conditions.
By letter dated May 5, 1961, the Commission also gave the St. Lawrence River Board discretionary
authority “to vary the outflow from Lake Ontario to provide beneficial effects or relief from adverse effects
to any interest when this could be done without appreciable adverse effects to other interests, within the
criteria and other requirements of the Order of Approval.” When the Commission approved the adoption of
Plan 1958-D in October 1963, it also renewed this discretionary authority vested in the Board of Control.
Discretionary deviations from plan flows are currently implemented by Control Board consensus and
direction and are categorized as short term (having durations of a few hours to weeks) or long term
(lasting for periods of weeks and months).
84 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows