Near Record Levels Still Prevail
Following wet conditions in October, drier and more seasonable conditions returned in November. Nonetheless, water levels of Lake Superior and Lake Michigan-Huron remain well above average.
The monthly mean level of Lake Superior in November was 183.78 m./602.95 ft., the third highest on record (1918 – present) and the highest since November 1985. Lake Michigan-Huron’s mean November level was 176.85 m./580.21 ft., the 12th highest on record and the highest since 1997.
The Lake Superior level at the beginning of December is 29 cm./11.5 in. above average, 15 cm./6 in. above the level recorded a year ago at this time and the fifth highest on record. The level of Lake Superior is expected to continue its seasonal decline in December.
Continuing Coastal Damage
The high levels coupled with strong winds and waves have resulted in shoreline erosion and coastal damages across the upper Great Lakes system. The International Lake Superior Board of Control says that additional shoreline erosion and coastal damages may occur this fall and winter should active weather continue.
Related November 14th Infosuperior Post: “Coastal Reporting Tool Displays Storm Damage“
The International Lake Superior Board of Control, under authority of the International Joint Commission (IJC), has set the Lake Superior outflow to 2,510 cubic metres per second (m3/s)/88639.81 cubic ft per second) for the month of December, effective Dec. 4. The December outflow is 100 m3/s/3531.5 cubic ft. per second more than that prescribed by Regulation Plan 2012.
Winter Outflow To Exceed Planned Rate
In consideration of the continuing high water levels in the upper Great Lakes and to accommodate expected maintenance at the hydropower plants in 2018, the Board recently received approval from the IJC to temporarily deviate from Plan 2012 this winter to continue to reduce the potential for adverse consequences of high and fluctuating flows in the St. Marys Rapids.
Over the winter months, the Board will release slightly more flow through the control structure at the head of the St. Marys Rapids by maintaining a gate setting equivalent to one gate fully open instead of the typical winter setting equivalent to one-half gate open.
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. The gates were lowered to this setting over 28-29 November. There will be no change to the setting of Gate #1, which supplies a flow of about 15 m /s to the channel north of the Fishery Remedial Dike.
Regional Water Supply Declines
The net water supplies to Lake Superior were below average in November. The level of Lake Superior fell 9 cm.3,5 in. last month, while on average the lake declines 5 cm./1.9 ” in November.
The net water supplies to Lake Michigan-Huron were also below average in November. The level of Lake Michigan-Huron fell 6 cm./2.3 in. last month, while on average the lake declines 4 cm/1.6″ in November.
The level of Lake Michigan-Huron is 47 cm./18.5 in. above its long-term average beginning-of-December level, 26 cm./10.2 in. higher than it was a year ago and the twelfth highest on record. The level of Lake Michigan-Huron is expected to continue its seasonal decline in November.
Related November 14th Infosuperior Post: “Interactive Tour – Lake Superior Outflows“
Related November 14th Infosuperior Post re October Water Levels: “Superior Almost One Foot Above Average“