Lake Superior water levels stay high, despite lack of precipitation

Although Thunder Bay-area residents didn't see much precipitation in January, Lake Superior is still very high.

The International Lake Superior Board of Control says the lake had the highest January level since 1997 — about 22 cm or 9 inches higher than the long-term average for the month.

The board’s Canadian secretary says that means the regulated outflows through a control structure at Sault Ste. Marie  will be fairly high in the spring and are currently at the maximum flow for winter — but it's hard to make any predictions beyond that.

“Lake Superior is a really tough watershed [to predict] in terms of spring snow melt ... it's very rocky as you know, pre-Cambrian shield,” Rob Caldwell said.

“The lake itself is, of course, the largest lake in the world.”

Caldwell said higher levels were expected heading into the winter because the 11 months before January were wetter than usual.

Press release from The International Lake Superior Board of Control:

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 2,400 cubic metres per second (m3/s) (84.8 thousand cubic feet per second (tcfs)) for the month of February, effective February 3rd. The outflow is being set to the normal maximum winter flow as prescribed by Plan 2012, the regulation plan for Lake Superior, and is about the same as the January flow.

The February outflow will be released by discharging approximately 2,308 m3/s (81.5 tcfs) through the three hydropower plants and passing most of the remaining flow through the control structure at the head of the St. Marys Rapids. The gate setting of the control structure for February will be maintained at the equivalent of one-half gate open (four gates open 20 centimeters (cm), (8 inches) (in) each). 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 monthly mean water level of Lake Superior in January was 183.54 m (602.16 ft). This is 22 cm (9 in) above the long-term (1918-2013) January average and the highest January level since 1997.

The net water supplies to Lake Superior were below average in January, ending an almost year-long streak of above-average supplies stretching back to February 2014. The level of Lake Superior declined 10 cm (4 in) last month, while on average the lake declines 7 cm (3 in) in January. The Lake Superior level at the beginning-of-February is 21 cm (8 in) above average, 25 cm (10 in) above the level recorded a year ago at this time, and 30 cm (12 in) above its chart datum level.

The monthly mean water level of Lake Michigan-Huron in January was 176.51 m (579.11 ft). This is 22 cm (9 in) above the long-term (1918-2013) January average, the highest January level since 1998.

The net water supplies to Lake Michigan-Huron were close to average in January. The level of Lake Michigan-Huron declined 2 cm (1 in), while on average the lake declines by 3 cm (1 in) in January. The level of Lake Michigan-Huron is 25 cm (10 in) above its long-term average beginning-of-February level, 56 cm (22 in) higher than it was a year ago, and 52 cm (20 in) above its chart datum level.

The levels of both Lakes Superior and Michigan-Huron are expected to continue their seasonal decline in February.