Some flooding of Whitefish Island trails to occur this month, board says

NEWS RELEASE

INTERNATIONAL LAKE SUPERIOR
BOARD OF CONTROL

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The International Lake Superior Board of Control, under authority granted to it by the International Joint Commission (IJC), has set the Lake Superior outflow to 3,230 cubic meters per second (m3/s) (114.1 thousand cubic feet per second (tcfs)) for the month of July, effective July 1st. The July outflow is 250 m3/s (8.8 tcfs) more than that prescribed by Regulation Plan 2012.

The July outflow of 3,230 m3/s (114.1 tcfs) is expected to exceed the combined capacities of the hydropower plants on the St. Marys River, which will be approximately 2,320 m3/s (81.9 tcfs) in July, and most of the remaining flow will be released through the control structure at the head of the St. Marys Rapids.

The gate setting of the control structure for the month of July will be increased on Wednesday, July 5th from the current setting equivalent to approximately four gates open to a setting equivalent to approximately five gates open. This will be achieved by partially opening each of Gates #2 through #15 to a setting of 84 cm (33 in) open. Anglers need to be cautious of the changing flows and water levels in the rapids on July 5th and the higher flows and levels that will be experienced in the rapids in July. There will be no change to the setting of Gate #1, which supplies a flow of about 15 m3/s (530 cfs) to the channel north of the Fishery Remedial Dike. Gate #16 will remain set to 5 cm (2 in) open to facilitate sea lamprey trapping.

Furthermore, some flooding of low-lying areas of Whitefish Island is expected as additional gates are opened and flows increase. As a result, some recreational trails and features in these areas will likely be inundated and may sustain damage, and users are encouraged to use extreme caution.

The July outflow is 250 m3/s more than that prescribed by Regulation Plan 2012. The Board expects to continue to adjust the outflow of Lake Superior in accordance with the approved deviation strategy to accommodate expected maintenance at the hydropower plants and reduce the potential for adverse consequences of high and fluctuating flows and water levels in the St. Marys Rapids.

Based on provisional data, the net water supplies to Lake Superior were above average in June. The level of Lake Superior rose 11 cm (4 in) last month, while on average the lake rises 7 cm (3 in) in June. The Lake Superior level at the beginning-of-July is 26 cm (10 in) above average, 8 cm (3 in) above the level recorded a year ago at this time, and 54 cm (21 in) above its chart datum level.

The net water supplies to Lake Michigan-Huron were above average in June. The level of Lake Michigan-Huron rose 11 cm (4 in) last month, while on average the lake rises 5 cm (2 in) in June. The level of Lake Michigan- Huron is 40 cm (16 in) above its long-term average beginning-of-July level, 12 cm (5 in) higher than it was a year ago, and 96 cm (38 in) above its chart datum level.

The levels of Lake Superior and Lake Michigan-Huron are both expected to continue their seasonal rise in July. 

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