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 2410 cubic metres per second (m3/s) for the month of December, effective December 3rd. The December outflow will be released by discharging about 2298 m3/s through the three hydropower plants and passing most of the remaining flow through the control structure at the head of the St. Marys Rapids.
This past week, the Board began to gradually decrease the gate setting of the control structure in preparation for winter. The gate setting, which was maintained at an equivalent of approximately five gates open at the start of November, was decreased to approximately three gates open November 25th, and to approximately one gate open November 26th. The gate setting will be further decreased to the equivalent of one-half gate open (four gates open 20 centimetres (cm) each) on December 3rd. The one-half gate equivalent setting is the normal winter maximum, and is typically maintained from December through April. There will be no change to the setting of Gate #1 which supplies water to the channel north of the Fishery Remedial Dike.
The December outflow of 2410 m3/s is 30 m3/s greater than that prescribed by Plan 1977-A. In April 2014, the Board requested and received approval from the IJC to temporarily deviate from Lake Superior Regulation Plan 1977-A to reduce the risk of unusually high flows expected in the St. Marys Rapids this summer. To offset some of the effects of releasing flows less than Plan 1977-A from June through September, flows greater than Plan 1977-A were released in May, and again from October through December 2014. By the beginning of January 2015, the net effect on lake levels resulting from this deviation strategy is expected to be negligible, at which time the Board expects to fully implement Plan 2012, the new regulation plan for Lake Superior.
The monthly mean water level of Lake Superior in November was 183.67 m. This is 21 cm above the long-term (1918-2013) November average and the highest November level since 1996.
For the tenth consecutive month, the net water supplies to Lake Superior were above average again in November. The level of Lake Superior declined 5 cm last month, which is the average amount the lake declines in November. The Lake Superior level at the beginning-of-December is 22 cm above average, 28 cm above the level recorded a year ago at this time, and 46 cm above its chart datum level.
The monthly mean water level of Lake Michigan-Huron in November was 176.54 m. This is 17 cm above the long-term (1918-2013) November average and the highest November level since 1997.
The net water supplies to Lake Michigan-Huron were also above average in November. The level of Lake Michigan-Huron remained at about the same level last month, while on average the lake declines 5 cm in November. The level of Lake Michigan-Huron is 20 cm above its long-term average beginning-of-December level, 54 cm higher than it was a year ago, and 54 cm above its chart datum level.
The levels of both lakes Superior and Michigan-Huron are expected to decline in December.
Mr. Jaymie Gadal is the Board Member for Canada. Brigadier General Richard Kaiser is the U.S. Board