FINAL REPORT - International Joint Commission

without developing the capability of the River for power generation. In 1924, the governments established
the Joint Board of Engineers to examine the technical issues raised by the Wooten-Bowden recommendations.
Reflecting decades of discussion and a number of Board reports, the Corps of Engineers submitted a
report in April 1942 entitled “St. Lawrence River Project, Final Report 1942.” This document formed the
basis for the ultimate planning and construction of the hydropower project and Seaway in the 1950s.
FINAL REPORT
Early Regulation Plans
The first regulation plan developed for Lake Ontario was a basic rule curve routing procedure developed
by the Canadian Department of Transport in September 1940. The plan specified eight “ideal” requirements
that a lake regulation method should fulfill. The plan centered around maintaining natural levels on
Lake Ontario and the St. Lawrence River and securing maximum dependable flows for power operation,
while avoiding difficulties downstream of the project around Montreal and its harbour.
High levels on Lake Ontario in the early 1950s caused substantial flood damage. As a result, the governments
sent a reference dated June 25, 1952, to the International Joint Commission requesting an investigation of
methods of regulation which could provide a measure of flood control. In April of the following year, the IJC
established the International Lake Ontario Board of Engineers as a result of this reference. On May 5, 1955,
the Board presented Plan 12-A-9 to the IJC. The Plan provided flood control at the expense of power
generation. The range of levels on Lake Ontario was set between a low of 74.15 m in the navigation season
and a high of 75.37 m (243.29 and 247.29 feet, respectively, referenced to the International Great Lakes
Datum (IGLD) 1985) based on the water supplies received in the 1860 to 1954 period. The Plan was not
implemented, but was used to calculate critical river profiles and design channel excavations for safe navigation
through the Seaway. The range of Lake Ontario levels, however, was retained in future plan development.
The International St. Lawrence River Board of Control (the Control Board), which was created by the
International Joint Commission on November 16, 1953, conducted all subsequent regulation studies.
On May 14, 1958, the Control Board recommended the adoption of Plan 1958-A “as the initial operating
plan for the regulation of the levels and outflows of Lake Ontario having in mind that certain revisions may
be necessary in the light of further studies and operating experience.” The Plan was put in operation on
April 20, 1960.
In 1960, low flow requirements of downstream navigation interests, particularly in Montreal Harbour,
resulted in re-examination of the Plan. The Control Board subsequently presented Regulation Plan 1958-C
on October 5, 1961, which was a revision of Plan 1958-A, designed primarily to reduce the frequency of
flows below those that would result in levels less than the low water datum in Montreal Harbour.
Improvements were accomplished by reductions in summer flows and minimum winter flows. The Plan
became operational on January 3, 1962.
On January 21, 1963, the IJC asked the Control Board to proceed with further studies “to provide, among
other possible benefits, for improvement of the levels of Montreal Harbour to the extent consistent with all
requirements of the Order of Approval.” The resulting Plan 1958-D, improved the Montreal Harbour levels
without reducing the minimum winter flows of Plan 1958-C. Plan 1958-D was put in operation in October
1963 and has remained the Lake Ontario regulation plan since that time.
Regulation Plan 1958-D
The data used in the development and testing of Plan 1958-D were identical to the data used in the 1958-A
and 1958-C versions; i.e., recorded water levels and supplies for the period 1860 to 1954, adjusted to
reflect March 1955 outlet conditions and net Great Lakes diversions as specified in the Commission’s 1956
Order of Approval.
Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows
3