Lake Ontario outflows reduced in light of a dry spring

Apr. 16—Outflows from Lake Ontario are being reduced in response to dry conditions that have caused lower water levels on the lake and the St. Lawrence River this spring. It now appears likely that lake levels will remain below long-term average over the summer, unless very wet weather occurs, the International Lake Ontario-St. Lawrence River Board announced.

Lake outflow reduction began on April 10. Reductions are below those specified in Plan 2014, to restore the extra water that was removed earlier this year to avert possible springtime flooding of the Lake Ontario shoreline.

Lake water restoration is occurring at the rate of approximately 0.8 inches (2 cm) per week for three weeks, then Plan 2014-prescribed outflows will be followed again, the board said.

Current lower water levels on the lake and the river are the result of reduced spring runoff, that is, lower than average precipitation and winter snowpack, according to the board.

During January and February, the board deviated from Plan 2014 and removed additional water from Lake Ontario, in response to a December 2020 risk analysis that showed a 28% chance of damaging high water levels in late spring-early summer 2021. A total of 3.7 inches (9.4 cm) was removed, under authority granted by the International Joint Commission.

Most summer 2021 forecast scenarios suggest that Lake Ontario levels will remain above critical low water level thresholds, the board said. Dry conditions also will likely result in significantly below average Lake St. Lawrence levels, and below average water levels on Lake St. Louis near Montreal, this spring and summer.