Update on Lake Superior Outflows and Expected Conditions - July 2024

The Board expects the total St. Marys River flow in July to be 2,450 m³/s (86,500 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.

Anglers and other users of the St. Marys Rapids need to be cautious of the increasing flows and water levels that will
be experienced in the rapids in July. The gate setting of the Compensating Works will be increased from the current
setting equivalent to four gates fully open (Gates #7 through #14 open 108 cm each) to a setting equivalent to
approximately six gates fully open. On Monday, July 8, Gates #9 through #15 will be raised to a setting of 135 cm
open and the St. Marys Rapids flow will increase from approximately 640 m³/s to 850 m³/s. The average St. Marys
Rapids flow in July is expected to be approximately 805 m³/s, to meet the Plan 2012-prescribed flow in July in
consideration of the capacity restrictions at the hydropower plants. Gate #1 will remain at its typical setting which
supplies a flow of about 15 m³/s to the channel north of the Fishery Remedial Dike. Gates #7 and #8 will remain
partially open 108 cm. Gate #16 will remain at 5 cm open to facilitate sea lamprey trapping.

Water level changes over the month of June
Water supply conditions were much wetter than average in the Lake Superior basin and wetter than average in the Lake Michigan-Huron basin in June.
 Lake Superior rose by 15 cm (5.9 in) last month while the seasonal long-term average pattern is for Lake Superior to rise by 8 cm (3.1 in) in June.
 Lake Michigan-Huron rose by 8 cm (3.1 in) last month, and the seasonal long-term average pattern is for Lake Michigan-Huron to rise by 5 cm (2.0 in) in June.

Water levels as of the beginning of July
 At the beginning of July, the lake-wide average water level of Lake Superior was 2 cm (0.8 in) above the seasonal long-term average (1918-2023) and 17 cm (6.7 in) below the level of a year ago.
 At the beginning of July, the lake-wide average water level of Lake Michigan-Huron was 11 cm (4.3 in) above the seasonal long-term average (1918-2023) and 1 cm (0.4 in) above the level of a year ago.

Forecast outlook
Both lakes are expected to continue their seasonal rise over the coming month.
 If weather and water supply conditions are near average, Lake Superior may rise by approximately 4 cm (1.6 in.) and Lake Michigan-Huron may rise by approximately 1 cm (0.4 in).
 If conditions are much wetter than average, Lake Superior may rise by as much as 11 cm (4.3 in) and Lake Michigan-Huron may rise by as much as 7 cm (2.8 in).
 If conditions are much drier than average, the water level of Lake Superior may drop by approximately 1 cm (0.4 in), and Lake Michigan-Huron may decrease by approximately 4 cm (1.6 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