Lake Ontario levels continue to decline as outflows reduced

By on September 2, 2019

Lake Ontario levels reached 247.7 feet and the record outflows of 367,270 cubic feet per second were reduced to 357,000 cubic feet per second on August 21, 2019. This flow rate is 7,060 cubic feet per second above the normal safe navigation flow limit that applies at the current Lake Ontario elevation as defined by the regulation plan. This flow represents a three percent reduction of outflows and remains a record-high value for this time of the year. The sustained record outflows of 367,270 cubic feet per second were maintained from June 13 through August 20, for a total of 69 days, 15 days longer than in 2017.

The outflow strategy for the remainder of 2019 is intended to sustain the accelerated decline of Lake Ontario levels through the end of the year. The International Lake Ontario – St. Lawrence River Board recognizes the need to address persistently elevated levels on Lake Ontario and remains committed to providing the highest achievable relief to Lake Ontario in consideration of the impacts of that relief on the St. Lawrence River interests.

Velocities increase because, as the lake level decreases, so does the water level within the upper part of the St. Lawrence River, reducing the amount of space for water being released to move in. Imagine the channel as a trough, and as the water level lowers, the depth of water in the trough decreases. For the same flow to go through that trough, the water has to move faster.

Given the current conditions, velocities are higher than usual throughout the river, and they are already causing unsafe cross-currents and erosion and are impacting boating, swimming and navigation. Sustaining or increasing velocities would cause conditions to become much worse.

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