Lake Superior

A little east of the middle of North America, Lake Superior (or gichigami in Ojibwe) retains the defining characteristics of a lake, but behaves like an inland sea. It has a small tide, busy international ports and 3-quadrillion gallons of water. That's:

  • 3,000,000,000,000,000 gallons (11.4-quadrillion liters)
  • Enough to submerge North and South America under 1 foot of fresh water
  • 10% of the world’s fresh surface water
  • Over half of the water contained in the Great Lakes

Lake Superior is the largest freshwater lake in the world by surface area and the third largest by volume. Scoured into its present form by the retreating glacial ice sheet covering the region during the last Ice Age (about 10,000 years ago), Superior’s cold waters are bounded by northern hardwood and conifer forests and buffeted by continental weather patterns. Three U.S. states and one Canadian province share Superior’s water prompting cooperative binational governance of human activities around the lake, which include managing:


Lake Superior is ultra-oligotrophic. This means it is very low in productivity (aquatic plant and algae production) compared to other lakes of the world. Its small watershed relative to its size and depth, geological “youth” (it is only roughly 10,000 years old, since the last ice age), and lack of well-developed soils all contribute to its low productivity. This means it cannot support as large or diverse a fish population as the other Great Lakes and is sensitive to changes caused by increased nutrients, invasive species, contaminants, and intensive land uses. Airborne contaminants such as mercury and toxaphere are proportionally more important in a lake like Superior, which receives less material from its watershed than many other lakes.

Lake Superior Facts:
Size: 31,700 miles2 82,100 km2
Deepest spot: 1,332 ft 406 m
Shoreline length: 1,826 miles 2,938 km
Watershed area: 49,300 miles2 127,700 km2
Volume: 3,000,000,000,000,000 gal 11,400,000,000,000,000 L
Long-term average outflow of water (1990-2007): 75,574 ft3/sec 2,140 m3/sec
Recent average outflow (1997-2007): 70,629 ft3/sec 2,000 m3/sec
Elevation: 600 ft above sea level 183 m
Avg. water temperature (2003-2007): 45° F 7° C
Avg. underwater visibility: 27 ft 8 m
# of vessels to Duluth/Superior port (2007): 1,231
# of fish species: 89 (31 native, 21 non-native)
Water retention/replacement time: 191 years
Tidal motion: About 1 inch About 2 cm
Avg. # of foggy days in Duluth: 52
Basin population: 425,548 U.S. citizens 181,573 Canadians
Est. tourists: over 3.5 million

Water in, annual average:
As rain or snow: 2.3 feet 70 centimeters
Through streams or ground water: 1.8 feet 55 centimeters
Mostly from the Nipigon River (Ontario) and St. Louis River (MN/WI)

Water out, annual average:
By evaporation: 1.6 feet 49 centimeters
Through St. Marys River into Lake Huron 2.5 feet 76 centimeters

This page last modified on July 22, 2014     © 1996 – 2014 Regents of the University of Minnesota     The University of Minnesota is an equal opportunity educator and employer.
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