MODIFICATION OF GREAT-LAKES REGULATION PLANS FOR SIMULATION OF MAXIMUM LAKE-ONTARIO OUTFLOWS

Nearly 50,000 years of Lake Ontario outflows were simulated and analyz ed as a part of the Hydro-Quebec Beauharnois-Les Cedres spillway rehab ilitation study. Historical Lake Ontario outflows could not be used fo r the study because of anthropogenic effects reflected in the data, th e statistically short record length, and autocorrelation of the data. Stochastically generated Great Lakes net basin supplies were used in a Great Lakes hydrologic response model to obtain Lake Ontario levels a nd outflows. A significant problem was the lack of robustness in the L ake Superior and Lake Ontario regulation plans during simulations with extreme water supplies. The regulation plans were modified consistent with the International Joint Commission's regulation criteria and pas t operational actions to give reasonable results under these condition s. The simulated Lake Ontario levels and flows had a greater range tha n those resulting from historical water supplies. The maximum simulate d Lake Ontario quarter-monthly level was 76.41 m (IGLD 55), and the ma ximum simulated quarter-monthly outflow was 14,160 m3s-1. The maximum- flow limitation of Lake Ontario's regulation plan, 8,780 m3s-1 was exc eeded 0.27% of the time. The upper lake-level regulation limit, 75.22 m, was exceeded 0.15% of the time. It was found that some of the regul ation criteria cannot be met simultaneously under extreme conditions. Historical water supplies, the current standard for the design and eva luation of modifications to the operational regulation plans, should n o longer be the sole test of the plans.