|Lake type||Formerly part of the Glacial Lake Agassiz, reservoir|
|Primary inflows||Winnipeg River, Saskatchewan River, Red River|
|Primary outflows||Nelson River|
|Catchment area||984,200 km2 (380,000 sq mi)|
|Basin countries||Canada, United States|
|Max. length||416 km (258 mi)|
|Max. width||100 km (60 mi) (N Basin)
40 km (20 mi) (S Basin)
|Surface area||24,514 km2 (9,465 sq mi)|
|Average depth||12 m (39 ft)|
|Max. depth||36 m (118 ft)|
|Water volume||294 km3 (71 cu mi)|
|Residence time||3.5 years |
|Shore length1||1,858 km (1,155 mi)|
|Surface elevation||217 m (712 ft)|
|1 Shore length is not a well-defined measure.|
Lake Winnipeg is a large, 24,514-square-kilometre (9,465 sq mi) lake in central North America, in the province of Manitoba, Canada, with its southern tip about 55 kilometres (34 mi) north of the city of Winnipeg. It is the largest lake within the borders of southern Canada, and it is part of the most undeveloped large watershed of southern Canada.
Lake Winnipeg is the sixth-largest freshwater lake in Canada, and the third-largest freshwater lake contained entirely within Canada, but it is relatively shallow (mean depth of 12 m (39 ft)) excluding a narrow 36 m (118 ft) deep channel between the northern and southern basins. It is the eleventh-largest freshwater lake on Earth. The east side of the lake has pristine boreal forests and rivers that are being promoted as a potential United Nations World Heritage Park. The lake is elongated in shape and is 416 km (258 mi) from north to south, with remote sandy beaches, large limestone cliffs, and many bat caves in some areas. Manitoba Hydro uses the lake as one of the largest reservoirs in the world. There are many islands in the lake, most of them undeveloped.
The lake's watershed measures about 984,200 square kilometres (380,000 sq mi), and covers much of Alberta, Saskatchewan, Manitoba, northwestern Ontario, Minnesota, and North Dakota. Its tributaries include:
- Saskatchewan River (through Cedar Lake)
- Red River (including Assiniboine River)
- Winnipeg River (draining Lake of the Woods, Rainy River and Rainy Lake)
- Dauphin River, (draining Lake Manitoba and Lake Winnipegosis)
- Bloodvein River (on the East side, draining from the Canadian Shield)
- Poplar River
- Manigotagan River
Lake Winnipeg drains northward into the Nelson River at an average annual rate of 2,066 cubic metres per second (72,960 cu ft/s), and forms part of the Hudson Bay watershed, which is one of the largest in the world. This watershed area was historically known as Rupert's Land when the Hudson's Bay Company was chartered in 1670.
Lake Winnipeg and Lake Manitoba are remnants of prehistoric Glacial Lake Agassiz, although there is evidence of a desiccated south basin of Lake Winnipeg approximately 4000 years ago. The area between the lakes is called the Interlake Region, and the whole region is called the Manitoba Lowlands.
It is believed that Henry Kelsey was the first European to see the lake, in 1690. He adopted the Cree language name for the lake: wīnipēk (ᐐᓂᐯᐠ), meaning "muddy waters". La Vérendrye referred to the lake as Ouinipigon when he built the first forts in the area in the 1730s. Later, the Red River Colony to its south took the lake's name for Winnipeg, the capital of Manitoba.
Lake Winnipeg lies along one of the oldest trading routes in North America to have flown the British flag. For several centuries, furs were traded along this route between York Factory on Hudson Bay (which was the longtime headquarters for the Hudson's Bay Company) over Lake Winnipeg and the Red River Trails to the confluence of the Minnesota and Mississippi Rivers at Saint Paul, Minnesota. This was a strategic trading route for the First British Empire. With the establishment of the Second British Empire that occurred after Britain's loss of the Thirteen Colonies, a quite significant increase in trade occurred over Lake Winnipeg between Rupert's Land and the United States.
Water conditions 
Because of its long, narrow shape, the lake exhibits a variety of interesting wind and wave effects, including temporary water level rises of up to one metre in height at its southern shore, a process called seiche. This occurs when prevailing northerly winds blow along the length of Lake Winnipeg, exerting a horizontal stress on its surface. Surface waters move in the direction of the wind and pile up along the leeward south shores.
Furthermore, water depths are known to be extremely variable at the south end of the lake. Many of the recreational beaches on the southern end of the lake feature rustic, seasonal piers for swimmers. It is not uncommon to be able to walk off the end of one of these piers one day into more than waist-deep water, then return a few days later to the same spot to find the water only ankle deep, or even exposed sand.
Setups greater than 1 m above normal lake levels have been recorded along many of southern Lake Winnipeg's recreational beaches, and the associated high waves with their uprush effects have caused considerable storm damage, backshore flood and shoreline erosion. The highest setups occur in the fall, when the northerly winds are strongest.
Algae population and pollution 
Lake Winnipeg is suffering from many environmental issues such as an explosion in the population of algae, caused by excessive amounts of phosphorus seeping into the lake, therefore not absorbing enough nitrogen. The phosphorus levels are approaching a point that could be dangerous for human health.
Communities on the lake include Grand Beach, Lester Beach, Riverton, Gimli, Winnipeg Beach, Victoria Beach, Pine Falls, Manigotagan, Berens River, Bloodvein, Sandy Hook, Hecla Village and Grand Rapids. A number of pleasure beaches are found on the southern end of the lake, which are popular in the summer, attracting many visitors from Winnipeg, about 80 km south.
Lake Winnipeg has important commercial fisheries. Its catch makes up a major part of Manitoba's $30 million-a-year fishing industry. The lake was once the main source of goldeye in Canada, which is why the fish is sometimes called Winnipeg goldeye. Common carp were introduced to the lake through the Red River of the North and are firmly established. Walleye (often called Pickerel in Manitoba) and whitefish together account for over 90 percent of its commercial fishing.
Because of its length, the Lake Winnipeg water system and the lake itself was an important transportation route in the province before the railways reached Manitoba. It continued to be a major transportation route even after the railways reached the province. In addition to aboriginal canoes and York boats, several steamboats plied the lake, including Anson Northup, City of Selkirk, Colvile, Keenora, Premier, Princess, Winnitoba, Wolverine and most recently the diesel powered MS Lord Selkirk II passenger cruise ship.
As depicted in Season 6 of the History Channel series Ice Road Truckers, once the lake freezes to a sufficient depth during the winter, it can be crossed by trucks hauling freight to isolated communities in Manitoba.
- Massive flood expected to take toll on Lake Winnipeg, feed algae blooms Winnipeg Free Press
- Great Canadian Lakes
- International Lake Environment Committee
- Fur Trade Canoe Routes of Canada/ Then and Now by Eric W. Morse Canada National and Historic Parks Branch, first printing 1969.
- $1.1M for Lake Winnipeg - Winnipeg Free Press
- Canada’s sickest lake, MacLean's Magazine
- "Lake Winnipeg at 'tipping point': report". CBC News. May 31, 2011.
- "Lake Winnipeg declared threatened lake of the year". Winnipeg Free Press. 2013-02-05.
- Manitoba Water Stewardship - Fisheries
- "A profile of Manitoba's commercial fishery". Manitoba Water Stewardship (Department, Government of Manitoba). 2010-05-14. Retrieved 2011-07-29.
- Canadian Action Party (2006) Canadian action party release on devils lake ruling
- Casey, A. (November/December 2006) "Forgotten lake", Canadian Geographic, Vol. 126, Issue 6, pp. 62–78
- Chliboyko, J. (November/December 2003) "Trouble flows north", Canadian Geographic, Vol. 123, Issue 6, p. 23
- Economist, "Devil down south" (July 16, 2005), Vol. 376, Issue 8435,. p. 34
- GreenPeace, "Algae bloom on Lake Winnipeg" (May 26, 2008). Retrieved February 2, 2009
- Daily Commercial News and Construction Record, "Ottawa asked to help block water diversion project: devils lake outlet recommended by U.S. army corps of engineers" (October 20, 2003), Vol. 76, Issue 198,. p. 3
- Sexton, B. (2006) "Wastes control: Manitoba demands more scrutiny of North Dakota’s water diversion scheme", Outdoor Canada, Vol. 34, Issue 1, p. 32
- Warrington, Dr. P. (November 6, 2001) "Aquatic pathogens: cyanophytes"
- Welch, M. A. (August 19, 2008) "Winnipeg’s algae invasion was forewarned more than 30 years ago", The Canadian Press
- Macleans (June 14, 2004) "What ails lake Winnipeg" Vol. 117, Issue 24, p. 38.
- Wilderness Committee (2008) "Turning the tide on Lake Winnipeg and our health"
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