Dry conditions lead to lower Lake Ontario water levels

Photo by Tom Rivers: The sun sets on March 20 on Lake Ontario in this photo taken from one of the piers at the Oak Orchard Harbor.

Posted 13 April 2021 at 10:57 am

Press Release, International Lake Ontario – St. Lawrence River Board

Lower than average precipitation and winter snowpack runoff have resulted in decreased inflows to Lake Ontario. The reduced inflows have resulted in lower water levels on Lake Ontario and the St. Lawrence River.

In response to these conditions, the International Lake Ontario – St. Lawrence River Board has decided to reduce outflows from Lake Ontario beginning April 10.

During January and February this year, the Board was deviating under authority granted by the International Joint Commission (IJC) to remove additional water from Lake Ontario as a result of the risk analysis in December 2020 showing approximately a 28% chance of water levels exceeding a damaging high water threshold in 2021. A total of 9.4 cm (3.7 inches) was removed from Lake Ontario to further reduce the risk of potentially damaging high water levels in late spring and early summer.

Due to the reduced spring runoff, the Board has decided to reduce outflows below those specified by the plan to restore the extra water removed during the winter to Lake Ontario at a rate of approximately 2 cm (0.8 in) of water to Lake Ontario per week for the next three weeks. After these 3 weeks, the Board will revert to plan-prescribed outflows.

This strategy will allow Lake Ontario and Lake St. Lawrence water levels to increase more than they would under plan-prescribed flows over the next few weeks. It now appears likely that Lake Ontario levels will remain below long-term average over the summer unless very wet weather occurs.