2021 is shaping up as a low water year following one of the lowest recorded annual periods of precipitation since 1950. The current forecasts are for about one more inch of water in Lake Ontario before June 1.
This excerpt below from an email on water levels received from Bryce Carmichael is well worth reading. Bryce is US Section Secretary for the International Lake Ontario St. Lawrence River Board, and has been working on this issue for many years.
The level of Lake Ontario and the upper St. Lawrence River is mostly dependent on the amount of water entering the lake both from the local basin and the inflow from Lake Erie. The International Lake Ontario – St. Lawrence River Board can influence the outflow from Lake Ontario through implementation of regulation plans, but this is far less significant than the natural factors affecting the water levels. Though current low water conditions are a primary concern of the Board’s and is being monitored closely, the current conditions are not unprecedented. Water levels are well within the historical fluctuation range and in the historical record the beginning of month level for May has been lower than the start of this month one quarter of the time, and the last time it was lower was 1 May 2010.
Recent data analysis of the Hydromet database from the Great Lakes Environmental Research Lab indicates that the amount of precipitation over Lake Ontario over the past 12 months has been at its lowest accumulated amount since records began in 1950. In particular, the last 90 days in the basin have seen well below average precipitation. This has been the major reason for the low levels of Lake Ontario we are now experiencing. It is important to note that given the very dry period we have seen over the last year, that no regulation plan or strategy would be able to remedy the impacts currently observed from low water. Regulation strategies that affect water levels on Lake Ontario change water levels by centimeters and inches not by meters and feet.
Although regulation of the outflows may result in small increases to the lake levels, the levels over the next 6 months will mostly depend on precipitation and non-controlled inflows from the upper Great Lakes. There is no method currently available to reliably forecast precipitation more than a few weeks into the future and thus decisions that are made by the board can only be based on the most up to date current information.
The Board is constantly monitoring all components of the water balance and making their decisions based on these observations as well as historical records and short term forecasts. In making these decision the Board must consider all the various interests in the basin both upstream and downstream of the control structure.
The most recent forecasts for Lake Ontario levels are available on the Board’s website:
We appreciate and value the communications received by those that live, work, and recreate within the Great Lakes. Please contact us with any additional questions or concerns.
Bryce Carmichael US Section Secretary
International Lake Ontario -St. Lawrence River Board
Telephone: (513) 684-2010