The Great Lakes

The Great Lakes — Superior, Michigan, Huron, Erie and Ontario — and their connecting channels form the largest fresh surface water system on earth. If you stood on the moon, you could see the lakes and recognize the familiar wolf head shape of Lake Superior, or the mitten bounded by lakes Michigan, Huron and Erie. Covering more than 94,000 square miles and draining more than twice as much land, these Freshwater Seas hold an estimated 6 quadrillion gallons of water, about one-fifth of the world’s fresh surface water supply and nine-tenths of the U.S. supply. Spread evenly across the contiguous 48 states, the lakes’ water would be about 9.5 feet deep.

The channels that connect the Great Lakes are an important part of the system. The St. Marys River is the northernmost of these, a 60-mile waterway flowing from Lake Superior down to Lake Huron. At the St. Marys rapids, the Soo Locks bypass the rough waters, providing safe transport for ships. The St. Clair and Detroit rivers, and Lake St. Clair between them, form an 89-mile long channel connecting Lake Huron with Lake Erie. The 35-mile Niagara River links lakes Erie and Ontario, and sends approximately 50,000 to 100,000 cubic feet of water per second over Niagara Falls; the manmade Welland Canal also links the two lakes, providing a detour around the falls. From Lake Ontario, the water from the Great Lakes flows through the St. Lawrence River all the way to the Atlantic Ocean, about 1,000 miles away.

This system greatly affects our way of life, as well as all aspects of the natural environment, from weather and climate, to wildlife and habitat. Yet for all their size and power, the Great Lakes are fragile. In the past, this fragile nature wasn’t recognized, and the lakes were mistreated for economic gain, placing the ecosystem under tremendous stress from our activities. Today, we understand that our health and our children’s inheritance depend on our collective efforts to wisely manage our complex ecosystem.