In a Nutshell:
- lake levels are better than 30 cm/ 1 ft. higher than this time last year
- 8 cm/ 3.14 in. above the previous record set in 1986
- record levels are expected to be sustained through July, August and September.
Lake Superior water levels are at a new record high. At the beginning of June, Lake Superior was 8 cm/3.14 in. above the previous record, set in 1986. Early June levels were 41 cm/16.14 in. above the long-term average between the years 1918 and 2018. New data for all of June, 2019 was not available at time of writing this article, but in May, 2019 the lake rose 13 cm/5.11 in. The lake normally rises 10 cm/3.9 in. each May.
At 1:20 P.M. on June 20th, Lake Superior’s water level stood at 183.91 m/603.40 ft., as measured at Duluth, Minnesota by the U.S. National Oceanic and Atmospheric Administration. One year earlier the average water level for June, 2018 was 183.56 m/602.23 ft. This represents a year-to-year water level rise of 35 cm/13.77 in.
Precipitation was near average in the Lake Superior watershed in May but despite this, water supply to the basin was above average from high winter precipitation and runoff.
Record High Levels All Summer
The U.S. Army Corps of Engineers predicts Lake Superior water levels will continue to rise over the next three months, reaching a peak in August. Record high levels are expected for July, August and September.
How Water Levels are Measured
Several water level gauges around Lake Superior are used to determine water levels. The gauges are maintained by the National Ocean Service of the National Oceanic and Atmospheric Administration in the U.S, and by the Canadian Hydrographic Service in Canada.
Water levels are measured in relation to elevation reference points, or benchmarks, around the Great Lakes. Based on these benchmarks, a single level surface is adopted as “chart datum” for a given lake, including Superior. In more technical terms, chart datum is referred to as “International Great Lakes Datum.” These elevation points are selected so that the water level for each lake will seldom fall below them. Only rarely will there be less depth available than what is portrayed on a nautical chart, or map.
Regulating Lake Superior Outflow
The International Lake Superior Board of Control is responsible for regulating the outflow of Lake Superior and managing the control works on the St. Marys River. The board points out that:
The ability to regulate the outflow from Lake Superior does not mean that full control of lake levels is possible. This is because the major factors affecting the water supply to the Great Lakes—over-lake precipitation, evaporation, and runoff—cannot be controlled; nor can they be accurately predicted in the long term. (ijc.org)
Data for this article was accessed from the following sources:
- U.S. Army Corps of Engineers
- National Oceanic and Atmospheric Administration- Great Lakes Environmental Research Laboratory.
- Canadian Hydrographic Service
- NOAA Great Lakes Water Level Viewer
- Great Lakes Water Levels Dashboard
- Real Time Data for Rivers Flowing to Lake Superior
Telephone Numbers for Lake Superior water levels/daily fluctuations at Canadian Guages:
- Thunder Bay – (807) 344-3141
- Rossport – (807) 824-2250
- Michipicoten – (705) 856-0077
- Gros Cap – (705) 779-2052.
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