Superior Almost One Foot Above Average
Posted on: November 14, 2017

This 39″ video shows the St. Marys River Rapids when the control structure is set to 6 gates open, the current setting.

Lake Still Rising in October

As of October, Lake Superior was still rising at a time of year when it usually goes down. The lake is now at the second highest November level ever recorded. The Lake rose 1.7 cm./.5 inches in October. The Lake usually loses about 3.81 cm./1.5 inches in October. The International Lake Superior Board of Control notes precipitation levels across the watershed, and flows from rivers and streams into the lake, far in excess of average. The lake is now 33.02 cm./13 inches above the November 1st average and 20.32 cm./8 inches above the level on November 1st last year.

Lake Still Rising in September

In its previous news release (October), The International Lake Superior Board of Control had the following to say about Lake Superior water levels:

  • net water supplies to Lake Superior were above average in September
  • the Lake Superior level at the beginning-of-October is 29 cm./11.4 inches above average
  • the level of Lake Superior rose 2 cm./0.78 inches in September
  • on average the lake declines 2 cm./0.78 inches in September
  • the lake is 10 cm./3.93 inches above the level recorded a year ago at this time
  • Superior is expected to begin its seasonal decline in October [this did not happen].

Click to view real time and historical data related to Lake Superior water levels including:

  • real time flow rates for rivers flowing to Superior
  • Great Lakes Water Level Viewer
  • Great Lakes Water Levels Dashboard.

Flow Rates At the Rapids

The International Lake Superior Board of Control set the Lake Superior outflow to 3,130 cubic metres per second (m3/s)/110534.9 cubic feet per second (ft3/s) for the month of October. (By way of comparison, outflow on the Nipigon River, the largest river entering the Great Lakes, on either the Canadian or U.S. sides, was at 393.5 cubic metres per second (m3/s)/13896.3 cubic feet per second (ft3/s) at time of writing this article.) The Board notes that St. Marys River flows exceed the amount of water that can be put through the 2 hydropower plants on the river, so the excess is put through the control structure at the top of the St. Marys Rapids.

Another fundamental consideration in flow rates is the critical St. Marys River fishery, for which flows must be maintained above a prescribed rate. The International Joint Commission has this to say about the fishery, “The St. Marys Rapids provide critical spawning, rearing and feeding habitat for a number of macroinvertebrate and fish species. Native whitefish, lake sturgeon, trout, perch and pike, along with more recently introduced species of salmon can all be found here, making this a world-class fishery, and also one of the top fly fishing destinations in North America.” The Board says the average St. Marys Rapids flow in October will be approximately 994 cubic metres per second (m3/s)/35102.7 cubic feet per second (ft3/s). (By way of comparison, the average flow in the Colorado River is 849.5 cubic metres per second (m3/s)/30,000 cubic feet per second (ft3/s).)

Whitefish Island
Whitefish Island is located in the Canadian side of the rapids. (Photo: J. Bailey/

Island Flooding

Whitefish Island, located on the Canadian side of the river in the rapids area has some very low-lying ground. Batchewana First Nation has built trails, boardwalks and gazebos for the public on the island, which is a popular recreation area. The Board urges anglers and other users of the St. Marys Rapids to remain extremely cautious of the high and changing flows and water levels that will be experienced in the rapids.  The Board notes that flooding of low-lying areas of Whitefish Island is expected and will likely cause some recreational trails and features to be inundated.


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