St. Clair River

The St. Clair River is a river in central North America which drains Lake Huron into Lake St. Clair, forming part of the International Boundary between the Canadian province of Ontario and the U.S. state of Michigan. The river is also a significant component in the Great Lakes Waterway with shipping channels permitting cargo vessels to travel between the upper and lower Great Lakes.



The river flows in a southerly direction, connecting the southern end of Lake Huron to the northern end of Lake St. Clair. It branches into several channels near its mouth at Lake St. Clair, creating a broad delta region.


The river is 39 miles (64 km) long and drops 5 feet (1.5 m) in elevation from Lake Huron to Lake St. Clair. The flow rate averages around 182,000 cubic feet per second (5,200 m³/s), and the drainage area is 222,400 square miles (576,000 km²). This takes into account that the combined drainage areas of Lakes Huron, Michigan, and Superior.

The shipping channel on Lake St. Clair itself is 35 miles (56 km) long from the end of the St. Clair River to the beginning of the Detroit River. The Detroit River is 32 miles (51 km) long and drops 3 feet (1 m) in elevation from Lake St. Clair to its mouth at Lake Erie. The Detroit River discharges an average of 186,000 cubic feet per second (5,300 m³/s) into Lake Erie.


In the 1700s, French Voyageurs travelled on the river in canoes loaded with furs destined to adorn Europe's royalty. Ships built at Marine City, Michigan during the mid-1800s carried immigrants up the river on their way to new homes in the American West. During the 20th century, freighters returned from the upper Great Lakes with iron ore, copper, grain - products of some of these settlers' labor.


The St. Clair River and its Lambton County tributaries in Ontario contributes 418 km² (103,210 acres) to the watershed, although this does not include the Sydenham River watershed. In Michigan, the Black River, Pine River, and Belle River drain 3,159 km² (780,600 acres) in Lapeer, Macomb, Sanilac, and St. Clair counties; the watersheds around Bunce Creek and Marine City are relatively small.


Stag Island lies between Corunna, Ontario and Marysville, Michigan.
Fawn Island is near Marine City, Michigan.
Walpole, Seaway, Bassett, Squirrel, Pottowatamie, St. Anne, Dickinson, and Harsens islands are located where the St. Clair River flows into Lake St. Clair; these islands form the "St. Clair Flats", the only major river delta in the Great Lakes and the largest freshwater delta in North America. Six of the islands in this delta are territory belonging to the Walpole Island First Nation.

Land usage

Most of the watershed away from the river in Ontario and Michigan is used for agriculture. A few forest and wetland remnants are present, although their area has declined significantly since European settlement.

Much of the shoreline on both sides of the St. Clair River is urbanized and heavily industrialized. Intensive development has occurred in and near the cities of Port Huron, Michigan and Sarnia, Ontario. The heaviest concentration of industry (including a large petrochemical complex) lies along the Ontario shore south of Sarnia.

Several communities along the St. Clair rely on the river as their primary source of drinking water. About one-third to one-half of the residents of Michigan receive their water from the St. Clair/Detroit River waterway.

Industries -- including petroleum refineries, chemical manufacturers, paper mills, salt producers and electric power plants -- also need high quality water for their operations, although there have been some cases in recent years where these industries have contaminated river waters after discharging pollutants.

Land habitat

Land areas of the St. Clair River shoreline and flats consist of two biological zones: upland and transitional, both of which are normally above the water table, but which may be flooded periodically.

The upland forests consist of deciduous species, many of which are near their northern climatic limit. Most pre-European settlement trees have been cleared for agriculture, industry, or urbanization. Remaining forest stands, such as oak savannas as well as lakeplain prairies, are found along the southern reaches of the river, particularly on the islands of the St. Clair River Delta and on the Michigan shore in Algonac State Park.

Transitional species are abundant in the low-lying regions, categorized as shrub ecotones, wet meadows, sedge marshes, and island shorelines and beaches. This habitat is home to water and land mammals, including humans, as well as songbirds, waterfowl, insects, pollinators, reptiles, and amphibians.

Water habitat

The aquatic habitat of the St. Clair River ranges from deep and fast near the Blue Water Bridge to shallow and slow in the lower river near its discharge point into Lake St. Clair.

Each area provides a unique habitat for aquatic life:

  • macrophytes (visible marine plants),
  • benthic macroinvertebrates (organisms that live at the bottom of a lake or stream),
  • phytoplankton and zooplankton (floating plants and animals),
  • emergent vegetation (plants seen above the water surface),
  • fish (from minnows to large sport fish).

Area of Concern

The St. Clair River is listed as an Area of Concern (AOC) because of pollutants such as bacteria, heavy metals, and toxic organics, which had come from municipal and industrial discharges, urban and rural runoff, combined sewer overflows (CSOs), and contaminated sediments.

The St. Clair River AOC includes the entire river, from the Blue Water Bridge to the southern tip of Seaway Island, west to St. Johns Marsh and east to include the north shore of Mitchells Bay on Lake St. Clair. Anchor Bay is not included.

Through the Great Lakes agreement, a Remedial Action Plan (RAP) was created to initiate cleanup measures. It consists of six steps:

  • Restrictions on fish consumption
  • Bird and animal deformities
  • Degradation of benthos
  • Restrictions on dredging activities
  • Restrictions on drinking water consumption
  • Beach closings
  • Degradation of aesthetics
  • Added cost to agriculture and industry
  • Loss of fish and wildlife habitat

The RAP for the St. Clair River AOC was initiated in 1985. A binational group, called the RAP Team, was established in 1987 to develop the plan and ensure adequate and appropriate public involvement. The RAP Team included representatives from federal, state, and provincial Clair River fr:rivière Sainte-Claire


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