LAKE-ONTARIO REGULATION UNDER TRANSPOSED CLIMATES

The implications of Lake Ontario regulation under transposed climates with changed means and variability are presented for seasonal and annu al time scales. The current regulation plan is evaluated with climates other than the climate for which it was developed and tested. This pr ovides insight into potential conflicts and management issues, develop ment of regulation criteria for extreme conditions, and potential modi fication of the regulation plan. Transposed climates from the southeas tern and south central continental United States are applied to thermo dynamic models of the Great Lakes and hydrologic models of their water sheds; these climates provide four alternative scenarios of water supp lies to Lake Ontario. The scenarios are analyzed with reference to the present Great Lakes climate. The responses of the Lake Ontario regula tion plan to the transposed climate scenarios illustrate several key i ssues: (1) historical water supplies should no longer be the sole basi s for testing and developing lake regulation plans; (2) during extreme supply conditions, none of the regulation criteria can be met simulta neously, priority of interests may change, and new interests may need to be considered, potentially requiring substantial revision to the Bo undary Waters Treaty of 1909; (3) revised regulation criteria should b e based on ecosystem health and socio-economic benefits for a wider sp ectrum of interests and not on frequencies and ranges of levels and fl ows of the historical climate; and (4) operational management of the l ake should be improved under the present climate, and under any future climate with more variability, through the use of improved water supp ly forecasts and monitoring of current hydrologic conditions.