Update on Upcoming Outflows and Expected Conditions – March 2026

The Board expects the total St. Marys River flow in March to be 1,930 m³/s (68,200 ft³/s) as prescribed by Regulation Plan 2012.

The gate setting of the Compensating Works at the head of the St. Marys Rapids will remain at the typical winter gate setting of one-half gate open (Gates #1 and #7 through #10 open 20 cm (8 in) each). The St. Marys Rapids flow will remain at approximately 85 m³/s or 3,000 ft³/s. The Poe Lock is scheduled to reopen on March 25, 2026.

Water level changes over the month of February

Water supply conditions were wetter than average in both the Lake Superior and Lake Michigan-Huron basins in February.

• Lake Superior remained within 1 cm of last month's level, while the seasonal long-term average pattern is for Lake Superior to decline by 4 cm (1.6 in) in February.
• Lake Michigan-Huron increased by 1 cm (0.4 in) last month while the seasonal long-term average pattern is for Lake Michigan-Huron to decline by 1 cm (0.4 in) in February.

Water levels as of the beginning of March

• At the beginning of March, the lake-wide average water level of Lake Superior was 9 cm (3.5 in) below the seasonal long-term average (1918-2024) and 9 cm (3.5 in) above the level of a year ago.
• At the beginning of March, the lake-wide average water level of Lake Michigan-Huron was 29 cm (11.4 in) below the seasonal long-term average (1918-2024) and 9 cm (3.5 in) below the level of a year ago.

Forecast outlook in March

• If weather and water supply conditions are near average, Lake Superior may decline by approximately 2 cm (0.8 in) and Lake Michigan-Huron may increase by approximately 5 cm (2.0 in).
• If conditions are much wetter than average, Lake Superior may increase by approximately 5 cm (2.0 in) and Lake Michigan-Huron may rise by approximately 13 cm (5.1 in).
• If conditions are much drier than average, the water level of Lake Superior may decrease by 7 cm (2.8 in), and Lake Michigan-Huron may decrease by about 3 cm (1.2 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 occurring during periods of severe weather and water supply conditions. Actual flows will vary hour-to-hour and day-to-day depending on hydrologic conditions and variations in flow at the hydropower facilities. Additional information can be found on the Board's homepage: https://ijc.org/en/lsbc.