St. Marys Rapids flows and water levels will increase in July
THUNDER BAY, SAULT STE MARIE, ONTARIO DULUTH, MINNESOTA July 2, 2022 (LSNews) Anglers and other users of the St. Marys Rapids, please be advised that the St. Marys Rapids flows and water levels will increase in July. As of Wednesday July 6, the St. Marys Rapids flow is expected to be approximately 786 cubic meters per second (m3/s) (27.8 thousand cubic feet per second (tcfs)). At these flows, some flooding of low-lying areas including recreation trails on Whitefish Island is expected, and everyone is encouraged to use extreme caution.
Outflows from Lake Superior and into Lake Michigan-Huron continue to be set in consideration of water levels upstream and downstream. The Board expects the total outflow to be 2,650 m3/s (93.6 tcfs) in July, which is prescribed by Lake Superior Regulation Plan 2012. Compensating Works Gates #7 through #12 will be raised to a setting of 175 cm (69 in) open on Wednesday, July 6. Gate #16 will remain partially opened to a setting of 5 cm (2 in) to provide improved efficiency of sea lamprey trapping conducted annually by the U.S. Fish and Wildlife Service. There will be no change to the setting of Gate #1, which supplies a flow of about 15 m3/s to the channel north of the Fishery Remedial Dike.
Water supplies were near average in the Lake Superior basin in June. Lake Superior rose 7 cm (2.8 in) last month, which is the seasonal long-term average rise in June. Water supplies were drier than average in the Lake Michigan-Huron basin in June. As a result, Lake Michigan-Huron rose 2 cm (0.8 in) last month, while on average the lake rises 6 cm (2.4 in) in June.
At the end of June, the lake-wide water level of Lake Superior is 12 cm (4.7 in) above the seasonal long-term average (1918-2021) and 3 cm (1.2 in) above the level of a year ago. At the end of June, the lake-wide level of Lake Michigan-Huron is 23 cm (9.1 in) above average, 16 cm (6.3 in) below the level of a year ago.
Depending on the weather and water supply conditions during the next month, Lake Superior may rise by as much as 10 cm (3.9 in) or may begin the seasonal decline. Lake Michigan-Huron water levels may rise by as much as 7 cm (2.8 in) in July or may begin the seasonal decline.
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||The International Lake Superior Board of Control is responsible for regulating the outflow of Lake Superior and managing the control works on the St. Marys River. Under any regulation plan, the ability to regulate the outflow from Lake Superior does not mean that full control of lake levels is possible. This is because the major factors affecting water supply to the Great Lakes, 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