Lake Michigan basin statistics
- Length: 307 mi (494 km)
- Breadth: 118 mi (190 km)
- Elevation: 577.5 ft (176 m)
- Depth: 279 ft (85 m) average; 923 ft (281 m) maximum
- Volume: 1,180 cubic mi (4,918 cubic km)
- Water surface area: 22,300 square mi (57,753 square km)
- Drainage basin area: 45,600 square mi (118,095 square km)
- Shoreline length: 1,640 mi (2,639 km), including islands
- Outlet: Straits of Mackinac to Lake Huron
- Retention or replacement time: 62 years
- Population: 12+ million*
* Includes metropolitan Chicago, which is not part of the drainage basin, but uses Lake Michigan for drinking water.
Lake Michigan’s main basin contains cold, clear, nutrient-poor water. This provides good habitat for trout, salmon, whitefish, and other coldwater species, but the amount of food available in open water has dropped in recent years. Open-water prey fish such as alewife and
bloater have declined dramatically since the 1980s.
Large rivers and associated inland lakes formed by drowned river mouths provide important habitat connections and nutrient inputs. In certain areas, excess nutrients create blooms of algae that die off and decompose, creating oxygen-deprived “dead zones.” Green Bay, considered the world’s largest freshwater estuary, is particularly vulnerable to these events. In shallow, rocky areas of the lake, excess nutrients can fuel the growth of bottom-dwelling algae that washes ashore and fouls beaches. The rotting algal muck can also harbor bacteria implicated in die-offs of fish and waterfowl in northern Lake Michigan.
Spawning fish often move into rivers or use rocky reefs in Lake Michigan’s main basin. Dam removal and management efforts have improved conditions for spawning fish in many rivers. Many rivers in the northeastern part of the basin support naturally-reproducing runs of introduced salmon.
Though 136 fish species appear in the Lake Michigan watershed, only 68 are found in the lake itself. Five deepwater cisco species disappeared from the lake due to overfishing and invasive species. Native strains of lake trout were also extirpated by the mid-1950s. Harvest limits, habitat restoration, water quality regulations, and stocking programs have aided in partial recovery of some species, including lake trout, cisco, lake sturgeon, and Great Lakes muskellunge.
Lake Michigan is the birthplace of the Great Lakes salmon fishery. Coho salmon were successfully stocked in the Platte River in 1966, and chinook salmon followed in 1967. Recreational salmon and trout fisheries have fluctuated over the past fifty years, but Lake Michigan still supports a large charter fishing fleet that primarily targets the “big five” salmonines: chinook salmon, coho salmon, steelhead (rainbow trout), brown trout, and lake trout.
Some bays and drowned river mouth lakes offer excellent fishing for other species, including walleye and smallmouth bass. Lake whitefish continues to be the most popular and valuable commercial species on Lake Michigan, although catches have declined in recent years. State-licensed commercial fishers operate in Wisconsin and Michigan waters, and tribal commercial and subsistence fisheries operate in 1836 Treaty waters of northern Lake Michigan. In Illinois and Indiana, commercial fisheries for yellow perch closed in 1997.
After Lake Erie, the Lake Michigan basin has the second highest population. Major urban centers include Chicago, IL; Milwaukee, WI; and Green Bay, WI, each relying on the lake for shipping, municipal, and industrial water use. Chicago also uses canals and water control structures to drain up to 2.1 billion gallons of Lake Michigan water per day into the Mississippi River. Originally designed for wastewater management, the canals also affect invasive species introductions, navigation, and flood control.
The basin is a mix of residential, agricultural, and forested land with the majority of undeveloped land found in the northern part. Many popular vacation destinations attract tourists to the Lake Michigan shoreline. The rocky points, islands, and protected bays of northern Lake Michigan are a draw for communities along Wisconsin’s Door Peninsula and Michigan resort towns like Petoskey and Traverse City. Sandy beaches and dunes stretch along most of Lake Michigan’s eastern shore from Indiana Dunes National Lakeshore in the south to Sleeping Bear Dunes National Lakeshore in the north.