Following the closure of the Seaway, and some partial and temporary ice formation in early January, mild temperatures across the Lake Ontario basin have allowed the International Lake Ontario - St. Lawrence River Board to set Lake Ontario outflows at unprecedented levels, higher than has ever previously been released in winter for several days and at times up to 10,700 cubic meters per second or 377,900 cubic feet per second.

These very high outflows are only possible under the current conditions and may only continue during a relatively short window before temperatures fall and ice formation resumes. At that time, outflows may need to be reduced to avoid disrupting the ice cover as it forms and stabilizes. However, if mild weather follows and ice conditions allow, outflows will be increased again as much and as soon as possible.

Even with unprecedented outflows from Lake Ontario the relative impact on the lake level will be small, during a time of year when water levels typically rise, with the key drivers for the lake levels being extremely high inflows from Lake Erie and any precipitation that continues to fall across the basin.

The board says it will continue to set outflows as high as possible based on changing conditions throughout the basin. In addition to ice formation in the St. Lawrence River, other critical conditions that have been identified over the past week of high outflows are maintaining a minimum water level difference upstream and downstream of Moses-Saunders Dam for safe operation and flow monitoring of the power generation plant, high water levels downstream of the dam specifically around Lake St. Louis, lower water levels on Lake St. Lawrence upstream of Moses-Saunders, and wind-driven water level changes.

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