Lake Superior is the largest of the Great Lakes in surface area and volume. Lake Superior could contain all the other Great Lakes plus three more lakes the size of Lake Erie. Water flows into the lake from many small rivers and streams. The Long Lac and Ogoki diversions in Canada channel water into Lake Superior that would otherwise flow into Hudson Bay. By order of the International Joint Commission, the lake's level, controlled by gates on the St. Marys River at Sault Ste. Marie, may not exceed 602 ft (183 m) above sea level. Each year a small percentage of the lake's water flows out through the St. Marys River, and it takes almost two centuries for the water to be completely replaced (retention time).
The Lake Superior drainage basin is rich in natural resources and scenic beauty. It is sparsely populated and economically dependent on its natural resources, which include metals, minerals, forests and recreation/tourism opportunities such as national lakeshores and national/state/provincial parks. It is particularly known for its clear, cold water and agate beaches. A circle tour guides highway travelers around the lakeshore. Many shipwrecks in Lake Superior are now protected in bottomland preserves and accessible to recreational divers. In 1985, scientists using a submersible vessel descended for the first time to the deepest part (-1,333 ft./-405 m) of Lake Superior near the Pictured Rocks National Lakeshore in Michigan waters.
Lake Superior contains 3 quadrillion gallons of water, that is 3,000.000.000.000.000 gallons of water. That’s ten percent of the world’s fresh surface water and one half of the water in the Great Lakes. Lake Superior contains enough water to flood all of Canada, the United States, Mexico and South America with one foot of water. The shoreline length of Lake Superior is 2,938 kilometers or 1826 miles.
What fills Lake Superior with water? Each year, 2.5 feet of water fall on the lake as rain or snow, and two more feet enter through ground water and approximately 20 rivers and streams, the largest of which are the mighty Nipigon River in Ontario and the St. Louis River in Minnesota. Of the 4.5 feet of water flowing into the lake each year, approximately 1/3 of this or 1.6 feet evaporates and the remainder flows to the lower Great Lakes through the St. Mary’s River at Sault Ste. Marie.