Update on Lake Superior Outflows and Expected Conditions - February 2024
Date

The Board expects the total St. Marys River flow in February to be 1,920 m³/s (67,800 cfs), as prescribed by

Regulation Plan 2012. Actual hour-to-hour and day-to-day flows may vary depending on hydrologic conditions, as

well as variations in flow from the hydropower plants.

The gate setting of the Compensating Works at the head of the St. Marys Rapids will be maintained in February at a

setting equivalent to approximately one-half gate fully open (Gates #7 through #10 open 20 cm (7.9 in)) and Gate #1 at its typical setting of 20 cm (7.9 in) open. St. Marys Rapids flow will be approximately 85 m³/s (3,000 cfs) in February.

The MacArthur Lock has been closed and will reopen April 24th. The Poe Lock has also been closed for the winter and will reopen on March 25th. These closures are routine for winter and allow for maintenance work.

Water level changes over the month of January

Water supply conditions were slightly below average in the Lake Superior basin and slightly above average in the

Michigan-Huron basin in January.

  • Lake Superior declined by 8 cm (3.1 in) last month, while the seasonal long-term average pattern is for Lake Superior to decline by 7 cm (2.8 in) in January.
  • Lake Michigan-Huron declined by 3 cm (1.2 in) last month, while the seasonal long-term average pattern is for Lake Michigan-Huron to decline by 2 cm (0.8 in) in January.

Water levels as of the beginning of February

  • At the beginning of February, the lake-wide average water level of Lake Superior was 2 cm (0.8 in) below the seasonal long-term average (1918-2022) and 21 cm (8.3 in) below the level of a year ago.
  • At the beginning of February, the lake-wide average water level of Lake Michigan-Huron was 10 cm (3.9 in) above the seasonal long-term average (1918-2022) and 2 cm (0.8 in) below the level of a year ago.

Forecast outlook

Both Lakes Superior and Michigan-Huron are in their seasonal decline.

  • If weather and water supply conditions are near average, both Lake Superior and Lake Michigan-Huron are expected to decline in February by approximately 5 cm (2.0 in) and 1 cm (0.4 in), respectively.
  • If conditions are wetter than average, Lake Superior may decline by 1 cm (0.4 in) and Lake Michigan-Huron may rise by 5 cm (2.0 in).
  • If conditions are drier than average, the water level of Lake Superior is expected to decline by as much as 9 cm (3.6 in), and Lake Michigan-Huron is expected to decline by as much as 6 cm (2.4 in).

The International Lake Superior Board of Control is responsible for managing the control works on the St. Marys River and regulating the outflow from Lake Superior into Lake Michigan-Huron. Under any outflow regulation plan, the ability to regulate the flow through the St. Marys River does not mean that full control of the water levels of Lake Superior and Lake Michigan-Huron is possible. This is because the major factors affecting water supply to the Great Lakes (i.e. precipitation, evaporation, and runoff) cannot be controlled, and are difficult to accurately predict. Outflow management cannot eliminate the risk of extreme water levels from occurring during periods of severe weather and water supply conditions. Additional information can be found at the Board’s homepage: https://ijc.org/en/lsbc or on Facebook at: https://www.facebook.com/InternationalLakeSuperiorBoardOfControl