Update on Lake Superior Outflows and Expected Conditions - November 2022
Anglers and other users of the St. Marys Rapids, please be advised that the St. Marys Rapids flows and water levels will remain above average in November. The gate setting of the Compensating Works will remain at the current setting equivalent to approximately six gates fully open. During this time, the flow through the rapids is expected to be approximately 920 cubic meters per second (m3/s) (32.9 thousand cubic feet per second (tcfs)). At these flows, some flooding of low-lying areas of Whitefish Island is expected, and as a result, some recreational trails and features in these areas will likely be flooded, and users are encouraged to use extreme caution. The gate setting will be lowered heading into the winter months.
Outflows from Lake Superior and into Lake Michigan-Huron continue to be set in consideration of water levels upstream and downstream. Due to ongoing maintenance at the Canadian hydropower facility, the International Lake Superior Board of Control (Board) anticipates that St. Marys River flows will be below those prescribed by Regulation Plan 2012 this winter. To help offset this, a flow of 2,500 m3/s (88.3 tcfs), which is 20 m3/s higher than the flow of 2,480 m3/s (87.6 tcfs) prescribed by Plan 2012, will be released in November.
Lake Superior declined by 7 cm (2.8 in) last month, while the seasonal long-term average decline in October is 3 cm (1.2 in). Lake Michigan-Huron declined by 8 cm (3.1 in) last month, while the seasonal long-term average decline in October is 7 cm (2.8 in).
At the beginning of November, the lake-wide water level of Lake Superior is 7 cm (2.8 in) above the seasonal long-term average (1918-2021) and 13 cm (5.1 in) above the level of a year ago. At the beginning of November, the lake-wide level of Lake Michigan-Huron is 16 cm (6.3 in) above average and 27 cm (10.6 in) below the level of a year ago.
Lake-wide average water levels of both Lake Superior and Lake Michigan-Huron are expected to continue to decline through the fall and into the winter months. Depending on the weather and water supply conditions during the next month, Lake Superior may decline by as much as 12 cm (4.7 in) in November. Similarly, the water level of Lake Michigan-Huron may also decline by as much as 12 cm (4.7 in) next month.
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