Lake Superior contains about 10% of the world’s surface freshwater.
That estimate refers to unfrozen surface freshwater, a category that includes lakes, rivers, and other exposed freshwater bodies. Lake Superior’s enormous volume makes it one of the most important freshwater reservoirs on Earth.
The lake is the largest of the Great Lakes by surface area and the deepest of them. Its cold water and great depth slow biological and physical processes, contributing to a long water-retention time compared with shallower lakes.
The figure is often confused with the share held by all five Great Lakes together. Collectively, the Great Lakes contain roughly one-fifth of the world’s surface freshwater, while Lake Superior alone accounts for about one-tenth.