This 29 km (18 mile) channel diverts water from the Assiniboine River, just west of Portage la Prairie, into Lake Manitoba near Delta Beach.
The removal of up to 25,000 cubic feet per second (cfs) of flood water provides flood protection for Winnipeg and areas along the Assiniboine River and also supports flood protection along the Red River north of Winnipeg.
The diversion protects several municipalities including Portage la Prairie, Cartier, St. Francis Xavier, Headingley, Woodlands and Macdonald. Communities that benefit include Portage la Prairie, Winnipeg, Oakville, Elie, Brunkild and La Salle.
Without the Portage Diversion, during an extreme event such as the 2011 flood, there would have been flooding to the south of the Assiniboine River; the river would have naturally spilled to Lake Manitoba and substantial flooding would have occurred north of the Assiniboine. Assiniboine River water would have overflowed all the way to the Municipality of Morris.
The Portage Diversion was built from 1965 to 1970 and cost $20.5 million.
During the flood of 2011, its capacity was increased for the short term to 34,000 cfs. Since 2011, about $6 million in repairs have been completed on various sections of the diversion.
The Shellmouth Dam, Portage Diversion and the Red River Floodway have prevented an estimated $7 billion in damages from flood waters.
The Portage Diversion is operated by raising gates in the Assiniboine River, when required, to divert a portion of the river through the diversion channel. There are also gates that control flow into the diversion channel.
Since its construction, the Portage Diversion has been operated 29 out of 43 years.