UPDATE ON LAKE SUPERIOR OUTFLOWS AND EXPECTED CONDITIONS - JANUARY 2018
Cold and snowy weather contributed to above-normal water supplies in the Lake Superior basin in December, while relatively drier conditions occurred in the Lake Michigan-Huron basin last month. Nonetheless, both lakes continue to see the effects of a wet spring and summer, and water levels of Lake Superior and Lake Michigan-Huron remain well above average as a result.
The monthly mean level of Lake Superior in December was 183.72 m, the 2nd highest on record (1918 - present) and the highest since December 1985. Lake Michigan-Huron’s mean December level was 176.79 m, the 12th highest on record and the highest since 1986. The high levels coupled with strong winds and waves have resulted in shoreline erosion and coastal damages across the upper Great Lakes system. As lake ice begins to form this may provide a level of protection to some areas of the shoreline, but additional shoreline erosion and coastal damages may occur this winter should active weather continue.
In consideration of the continuing high water levels in the upper Great Lakes, the International Lake Superior Board of Control, under authority granted to it by the International Joint Commission (IJC), will continue to release outflows of up to 2,510 cubic metres per second (m3/s) through the winter months. This flow is 100 m3/s more than the normal winter maximum prescribed by Regulation Plan 2012. Actual outflows may vary depending on hydrologic and ice conditions, as well as maintenance activities at the hydropower plants on the St. Marys River, all of which have been directed to flow at their maximum available capacity.
The gate setting of the control structure will be maintained at the current setting (eight gates open 26 cm each, which is equivalent to approximately one gate fully open) during the month of January. This setting is expected to continue throughout the winter, as is typically the case when gates become frozen in ice. Likewise, there will be no change to the setting of Gate #1, which supplies a flow of about 15 m3/s to the channel north of the Fishery Remedial Dike.
The net water supplies to Lake Superior were well above average in December. The level of Lake Superior fell 2 cm last month, while on average the lake declines 8 cm in December. The Lake Superior level at the beginning-of-January is 34 cm above average, 20 cm above the level recorded a year ago at this time and the 2nd highest on record. The level of Lake Superior is expected to continue its seasonal decline in January.
The net water supplies to Lake Michigan-Huron were below average in December. The level of Lake Michigan-Huron fell 9 cm last month, while on average the lake declines 5 cm in December. The level of Lake Michigan-Huron is 43 cm above its long-term average beginning-of-January level, 25 cm higher than it was a year ago and the 15th highest on record. The level of Lake Michigan-Huron is expected to continue its seasonal decline in January.