Image of St. Marys River Control Structures

2019 High Water Levels Questionnaire and Update on Conditions


Wet conditions throughout the upper Great Lakes basin in 2019 resulted in record and near record-high water levels on Lake Superior and Lakes Michigan-Huron. These high water levels have directly impacted many of you that live and work along the upper Great Lakes shoreline. The International Lake Superior Board of Control (Board) is interested in gathering more information on how high water level conditions have impacted individuals and communities along the upper Great Lakes shoreline.

Through the International Joint Commission’s (IJC) Great Lakes – St. Lawrence River Adaptive Management (GLAM) Committee, a subcommittee of the Board, an on-line questionnaire has been developed that allows impacted shoreline property owners to report directly on their experiences in 2019. The questionnaire includes opportunities to describe the types and extent of high water impacts, as well as upload photos to illustrate those impacts. Responses will be summarized by the GLAM Committee as part of its reporting to the Board and the IJC. The results will also be used to better predict potential impacts under a range of possible future water level conditions.  Further information, including a link to the questionnaire itself, is available on the GLAM Committee website ( 

Wet weather continued in September, causing Lake Superior water levels to rise by 4 cm over the course of the month, while on average the water level declines 1 cm in September.  The monthly mean level in September of 183.86 m ties the record set in 1985, and at the beginning of October, Lake Superior is 1 cm above the record-high beginning-of-month level set in 1985. The level is currently 35 cm above average (1918 – 2018) and 18 cm above its level of a year ago.

Lake Michigan-Huron also rose 4 cm over the course of September, while on average the water level declines 6 cm in September. Lake Michigan-Huron is currently 19 cm below the record-high beginning-of-month level set in 1986. The level is 83 cm above average, and 42 cm above last year’s beginning-of-October level.  

Lake Superior and Lake Michigan-Huron are expected to resume their seasonal declines in October, but will remain near record-highs for this time of year. As a result, there will continue to be a significantly increased risk of shoreline erosion, lakeshore flooding and coastal damages over the next several weeks and potentially through the fall. The Board advises all those that may be affected to prepare for potentially severe coastal impacts, especially during periods of strong winds and high waves.

The Board expects the total outflow from Lake Superior to be 2,880 m3/s in October, which is as prescribed by Lake Superior Regulation Plan 2012.  Actual outflows may vary depending on hydrologic conditions, as well as maintenance activities at the hydropower plants on the St. Marys River. The gate setting at the Compensating Works will be decreased to the equivalent of six gates fully open. Gates #8, #9, #10 and #14 will be partially lowered on October 7th.

The average St. Marys Rapids flow in October is expected to be approximately 1,047 m3/s. Anglers and other users of the St. Marys Rapids need to be cautious of the high flows and water levels that will continue to be experienced in the rapids in October. Furthermore, some flooding of low-lying areas of Whitefish Island is expected to continue at these high flows. As a result, some recreational trails and features in these areas will likely be inundated and may sustain damage. Users are encouraged to use extreme caution.