Lake Ontario water levels continue to drop; IJC releases summer outlook

Weather Blog

ROCHESTER, NY (WROC) — The International Joint Commission (IJC) and the Lake Ontario-St. Lawrence River Board (LOSLRB) continue to regulate outflows at the Moses-Saunders dam according to Plan 2014 taking into account multiple different interests.

That includes, but is not limited to the homeowners on Lake Ontario, the shipping industry, the boating industry, hydro-electric power, drinking water quality, the environment, and others.

The IJC summer 2020 newsletter is out now and can be found here.

2020 inflows into Lake Ontario have been less than 2019 even with record high Lake Ontario water levels. Below is a look at Net Total Flow into Lake Ontario. Note the 2020 line (dark blue) is lower than 2019 (light blue) and much lower than 2017 (light green).

The lower inflow as well as lack of high water upstream opened the door to allow for continued deviations of Plan 2014 for maximum outflow through the winter and spring months. Outflow has been over 300,000 Cubic Feet per Second (CFS) for much of the year.

The deviation from Plan 2014 started in June 2019 and continued for an entire year with the goal to remove as much water as possible. The formation of ice along the St. Lawrence River downstream of Lake Ontario can force the LOSLRB to reduce flows to prevent damage to intake valves, but that only happened a few times this year.

Precipitation compared to average for February, March, April, and May 2019.

Green: Above Average

Red: Below Average

This was a year of record flooding.

Precipitation compared to average for February, March, April, and May 2020.

Green: Above Average

Red: Below Average

No flooding this year.

Data is from Columbia University. Note the differences between amount of precipitation compared to average for the two years. There is a significant difference around the Lake Ontario water basin. Lake Ontario peaked on May 5. That is when the planning board returned to Plan 2014 and is continually monitoring the situation downstream to see if further adjustments need to be made.


As of June 30, Lake Ontario is releasing about 325,600 cfs through the Moses-Saunders Dam. That is exceeding the inflow of about 297,700 cfs. Expect water levels to continue to slowly drop through the summer. The forecast is for lower levels through September, but the uncertainty grows as you get further in time. Much of it will depend on how much precipitation falls.

As of early June, Plan 2014 is under review by a board consisting of members that have been impacted by Lake Ontario flooding in 2017 and 2019. Pending this review, there may or may not be changes to how the outflows will be regulated heading into 2021.

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