Author(s): T. E. Wigle; J. Bartholomew; C. J. R. Lawrie
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Abstract: The St. Lawrence Seaway and Power Project, constructed jointly by Canada and the United States during the period 1954 to 1958, brought about very significant changes to the regime of the St. Lawrence River, including a plan for regulating the outflow from Lake Ontario. These changes were particularly significant in the 170 km International Rapids Section of the river stretching from Lake Ontario to Cornwall, where construction of the Power Dam and associated control works resulted in elimination of the numerous rapids by creation of the new Lake St. Lawrence behind the Dam. The impact of winter ice conditions in this new regime was, and continues to be, a very important factor which is carefully tested and evaluated by the Power Entities in their winter operations, and which has required the establishment of certain ice control features and operating techniques. The regulation plan for controlling Lake Ontario levels and the economics of power production depend upon the capability of this critical section of the river to pass the prescribed volume of water through the channels during the winter months. This capability is achieved through the establishment of a smooth and stable ice cover by reducing velocities in the various channel reaches. This in turn requires a reduction in the outflow of Lake Ontario and results in sacrificing power generation on the short-term, while the ice cover forms, for the sake of greater reliability of power production and regulation on the long-term. Constant monitoring of the variables which influence the rate and quality of ice formation and the degree of stabilization achieved takes place during the initial freeze-up period, the mid-winter period, and the break-up period. Winter operations are influenced by the hydrologic conditions on the Great Lakes basin and the meteorologic, hydraulic, and physical conditions of the International Rapids Section.
Year: 1981