Lake Michigan is not naturally connected to the world’s oceans through direct river systems. Its waters are part of the larger Great Lakes basin, which historically drained eastward. Human engineering has created pathways for commercial navigation and the movement of water and organisms to and from oceanic systems. These connections involve the lake’s natural drainage patterns and human modifications.
Lake Michigan’s Natural Hydrology
Lake Michigan is one of North America’s five Great Lakes, sharing its water level and a direct connection with Lake Huron through the Straits of Mackinac. Hydrologically, these two lakes are often considered a single body of water. Water naturally flows from this combined system eastward into Lake Erie via the Detroit River, then over Niagara Falls into Lake Ontario.
From Lake Ontario, water flows into the St. Lawrence River, which eventually empties into the Atlantic Ocean. This eastward flow represents the primary natural drainage pathway for the Great Lakes basin. Lake Michigan’s connection to Lake Huron ensures its waters are part of this extensive freshwater system that ultimately reaches the Atlantic.
Engineered Waterway Connections
Human engineering has altered the Great Lakes’ natural hydrology, creating two primary connections to oceanic systems. The St. Lawrence Seaway, a joint Canadian and U.S. project completed in 1959, enables ocean-going vessels to navigate from the Atlantic Ocean deep into the Great Lakes. This system includes locks, canals, and channels that bypass natural obstacles along the St. Lawrence River, extending navigation as far inland as Lake Superior. Vessels up to 740 feet long and 78 feet wide can transit these waterways, linking North America’s industrial heartland to global maritime trade routes.
A different connection links Lake Michigan to the Gulf of Mexico via the Mississippi River system. The Chicago Sanitary and Ship Canal, completed in 1900, was engineered to reverse the flow of the Chicago River. This project diverted Chicago’s sewage away from Lake Michigan, the city’s drinking water source, sending it instead towards the Des Plaines River and the Mississippi River basin. This 28-mile-long canal created a navigable link between the Great Lakes Waterway and the Mississippi River system, providing a pathway for commercial barges and pleasure boats to reach the Gulf of Mexico.
Implications of Interconnected Waterways
The engineered connections of Lake Michigan to the ocean affect commerce, ecosystems, and water resource management. Commercial shipping through the St. Lawrence Seaway facilitates trade, allowing goods like grain, iron ore, and steel to move between the North American interior and international markets. This maritime network generates billions in economic activity and supports hundreds of thousands of jobs across Canada and the United States, contributing to the region’s economic vitality.
The connections also pose environmental challenges, particularly concerning the spread of aquatic invasive species. The Chicago Sanitary and Ship Canal, while crucial for navigation and sanitation, has become a pathway for non-native species to move between the Great Lakes and Mississippi River basins. Species like Asian carp, zebra mussels, and round goby have utilized this corridor, impacting native ecosystems and local economies. Efforts, such as electric barriers, aim to deter the movement of these species and protect the ecological balance of both water systems.
Water management and diversion are issues influenced by these interconnected waterways. The Chicago diversion, through the Sanitary and Ship Canal, represents a significant transfer of water out of the Great Lakes basin into the Mississippi River system. This diversion, along with other water transfers, influences water levels and resource allocation within the Great Lakes. Cooperative agreements and management plans, such as the Great Lakes Compact, aim to address these water resource challenges by regulating diversions and promoting sustainable practices across the basin.