Saint Lawrence Seaway

The Saint Lawrence Seaway in its broadest sense is the system of canals that permits ocean-going vessels to travel from the Atlantic Ocean to the Great Lakes as far as Lake Superior. However, according to law, the Saint Lawrence Seaway extends from Montreal to Lake Erie and includes the Welland Canal while the upper section is the Great Lakes Waterway.

The seaway begins at the port of Montreal, where the South Shore Canal (St-Lambert and Cte Ste-Catherine canal locks) passes the Lachine Rapids. West of the Island of Montreal and Lac Saint-Louis, the Beauharnois canal and locks pass the Beauharnois hydroelectric dam. The seaway then leaves Quebec through Lac Saint-Franois and the Akwesasne Mohawk First Nation, and passes through New York State and Ontario. In New York, the Wiley-Dondero Canal (Snell and Eisenhower locks) passes the Moses-Saunders power dam, and the short Iroquois lock passes the Iroquois water level control structure. Altogether there are seven locks in the Montreal-Lake Ontario section (5 Canadian, 2 American).

The Welland Canal (eight locks) links Lake Ontario to Lake Erie, bypassing the formidable barrier of Niagara Falls.

The Sault Ste Marie locks bypasses the rapids on St. Marys River connecting Lake Superior with Lake Huron. They are operated toll-free by the U.S. Army Corp of Engineers[1] ( and not by the St Lawrence Seaway Management Corporation. Thus they are often not considered part of the St Lawrence Seaway although in practice they are an integral part of the Great Lakes navigation system.

The seaway is co-administered by Canada and the United States. It was first used on April 25, 1959, although it was not officially opened until June 26th, 1959 by Queen Elizabeth II and President Dwight D. Eisenhower.

To create a navigable channel through the Long Sault rapids and allow hydroelectric stations to be established at Cornwall, Ontario and Massena, New York, a man-made lake, Lake Saint Lawrence, was created. This required the inundation on July 1, 1958 of ten villages in Ontario, now collectively known as "The Lost Villages."

The creation of the Seaway also led to the introduction of foreign species of aquatic animals, including the sea lamprey and the zebra mussel, into the Great Lakes watershed.

Lock and channel dimensions

The size of vessels that can traverse the seaway is limited by the size of locks. Locks on the St Lawrence, and on the Welland Canal are 766 feet (233.5 m) long, 80 feet (24 m) wide, and 30 feet (9.1 m) deep. The maximum allowed vessel size is slightly smaller: 740 feet (225.6 m) long, 78 feet (23.8 m) wide, and 26 feet (7.9 m) deep; many vessels designed for use on the Great Lakes following the opening of the seaway were built to the maximum size permissible by the locks, also known informally as Seaway-Max. Larger vessels of the lake freighter fleet are built on the Lakes and can never travel down the Seaway to the ocean. The only lock on the Great Lakes Seaway is 1,200 feet (356.8m) long, 110 feet (33.5 m) wide and 32 feet (9.8 m) deep although the channels are not kept that deep.

Water depth is another obstacle to vessels, particularly in connecting waterways such as the St. Lawrence River. The depth in the channels of the St. Lawrence Seaway is 12.5 m (41 ft) downstream of Quebec City, 10.7 m (35 ft) between Quebec City and Deschaillons, 11.3 m (37 ft) to Montreal, and 8.2 (27 ft) upstream of Montreal. Channels in the Great Lakes Waterway section are slightly shallower: 7.62m - 8.2m (25 to 27 ft).

Channel depths when combined with the limited lock sizes mean that only 10% of the ships currently travelling on the world's oceans can traverse the entire Seaway. Proposals to expand the Seaway, dating from as early as the 1960s, have been rejected as too costly, environmentally and economically. Lower water levels in the Great Lakes have also posed problems for some vessels in recent years.

Earlier canals

In 1862, locks on the St Lawrence allowed transit of vessels 186 feet long, 44 feet wide, and 9 feet deep. The 1862 Welland Canal allowed transit of vessels 142 feet long, 26 feet wide, and 10 feet deep.

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