Assiniboine River

The Assiniboine River (/əˈsɪnɪbɔɪn/; French: Rivière d'Assiniboine) is a 1,070-kilometre (660 mi) river that runs through the prairies of Western Canada in Saskatchewan and Manitoba. It is a tributary of the Red River. The Assiniboine is a typical meandering river with a single main channel embanked within a flat, shallow valley in some places and a steep valley in others. Its main tributaries are the Qu'Appelle, Souris and Whitesand Rivers. For early history and exploration see Assiniboine River fur trade.

Assiniboine River
A view of the Assiniboine River looking southeast from the Maryland Bridge in Winnipeg
Red River drainage basin, with the Assiniboine River highlighted
Location
CountryCanada
Provinces
Physical characteristics
SourceWindy Lake east of Kelvington
 • locationSaskatchewan
 • coordinates52°18′15″N 103°06′01″W
 • elevation640 m (2,100 ft)
MouthRed River of the North
 • location
The Forks in Winnipeg, Manitoba
 • coordinates
49°53′09″N 97°07′44″W
 • elevation
230 m (750 ft)
Length1,070 km (660 mi)
Basin size182,000 km2 (70,000 sq mi)
Discharge 
 • average45 m3/s (1,600 cu ft/s)
Basin features
River systemRed River drainage basin
[1][2]

The river takes its name from the Assiniboine First Nation. Robert Douglas of the Geographical Board of Canada (1933) made several comments as to its origin: "The name commemorates the Assiniboine natives called by La Vérendrye in 1730 'Assiniboils' and by Governor Knight in 1715 of the Hudson's Bay Company 'stone Indians.' Assiniboine is the name of an Indian tribe and is derived from 'assine' a stone and 'bwan' native name of the Sioux, hence Stony Sioux name was possibly given because they used heated stones in cooking their food."[3]

Course
Junction of the Red and Assiniboine rivers in Downtown Winnipeg

The Assiniboine River rises in eastern Saskatchewan east of the community of Kelvington on the upper prairie level above the Manitoba Escarpment. The Assiniboine River flows through three basic zones with different channel characteristics. Upstream of Brandon, the main stem of the river and its most important tributaries flow within a very large valley. The valley was cut by huge glacial melt water flows at the end of the last glaciation. The floor of this spillway valley provides a natural floodplain for the river and the valley provides a significant storage volume making the construction of the Shellmouth Dam north of Russell both technically and economically viable. The major tributaries in this reach are the Qu'Appelle, Shell and Little Saskatchewan Rivers.

The glacial flows created a large delta east of Brandon extending almost to Portage la Prairie. The river has eroded down through sediments of the delta cutting a narrow valley through these sediments as it drops through a vertical distance of about 150 metres (490 ft) to the Lake Agassiz – Red River Plain . In this valley, the river is confined with a narrow valley floor. The Souris River is the primary tributary contributing flow to the Assiniboine in this reach. Near Portage la Prairie the river emerges from the delta reach onto the relatively flat Red River plain (the floor of former Glacial Lake Agassiz) and at this point it can flow in any direction from roughly northwest to roughly southeast. The gradient of the river channel within the delta reach to the west is relatively high, so the river water velocities are fairly high and the waters of the river carry significant amounts of sediment. The gradient in the flat Red River plain is much less and the velocity of the river water flowing over this plain is much lower. Therefore, the sediments carried by the river waters as they flow through the delta reach are deposited onto the plain. The Assiniboine winds its way east eventually joining the Red River at "The Forks" in Winnipeg, Manitoba.

Today, Assiniboine Herald at the Canadian Heraldic Authority is named after the river. Asessippi Provincial Park, an RV park was built on the east shore of the Shellmouth Reservoir.

Tributaries include the Whitesand River which joins it near Kamsack, Saskatchewan, the Souris River, which joins it near Wawanesa, Manitoba, the Birdtail River which joins at the Birdtail Sioux First Nation, the Little Saskatchewan, which joins west of Brandon, and the Qu'Appelle River, which joins near the site of the Hudson's Bay Company historic Fort Ellice site.

Flow rates and flood potential
The Assiniboine River flooding the Forks Marina in Winnipeg

There are three hydrometric stations on the river that have been taking measurements since 1913. The Assiniboine River near Headingley has an average discharge of 45 cubic metres per second (1,600 cu ft/s).[4] One millimeter of runoff from half the watershed would take 70 hours to drain at flow rates of 360 cubic metres per second (13,000 cu ft/s). The following discharge rates were recorded during the 1995 flood:[5]

Location Peak flow, 1995
(m3/s)		 Mean flow, April '95
(m3/s)		 Mean flow, May '95
(m3/s)		 Max flow, date
(m3/s)
Russell 360
May 4		 34.2 46.3 504
April 29, 1922
Brandon 566
April 26		 81.1 104.0 651
May 7, 1923
Headingley 300
April 20		 115.0 142.0 614
April 27, 1916

It is prone to spring flooding. Some flood flows can be diverted into Lake Manitoba at Portage la Prairie. In 1967, the Shellmouth Dam was built in Shellmouth to help reduce flood peaks and to supplement flows during dry periods. The Portage Diversion was completed in 1970. Despite these efforts, in May 2011 it was necessary to breach one of the dikes beside the river to relieve flood stresses east of Portage la Prairie. A Manitoba-wide state of emergency was declared in the wake of one in three hundred-year floods on the Assiniboine River at Brandon.[6][7][8] Below are the actual observed flow rates for major floods at different locations along the river:

Location 1882 Peak Flow (cfs) (Estimated) [9][10] 1976 Peak Flow (cfs) [11] 2011 Peak Flow (cfs) [9] 2014 Peak Flow (cfs) [12][13] 2017 Peak Flow (cfs) [14][15][16]
Brandon 43,000 21,700 36,700 38,870 23,500
Portage la Prairie 51,414 49,000 53,100 52,100 39,000
Headingley 32,000 21,700 19,200 TBD 15,360
  • Note: Flows in 1882 occurred before any flood protection measures such as the Shellmouth Reservoir and Portage Diversion were built.

Looking specifically at the Assiniboine River at Portage La Prairie, where maximum river flows occur prior to historical spillovers (prior to construction of the Portage Diversion and the Lower Assiniboine River Dikes) into the watersheds of Lake Manitoba and the La Salle River, the top 10 calculated natural peak flow rates before construction of the current flood infrastructure are:

Year Calculated peak flow (cfs)[17][18]
1882 51,414
1902 32,322
1904 41,806
1974 30,121
1976 50,137
1995 31,551
2009 27,202
2011 60,114
2014 54,369
2017 40,350

Fauna

Fish species include walleye, yellow perch, northern pike, mooneye, burbot, channel catfish brown bullhead, rock bass, white sucker, shorthead redhorse and common carp.

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See also

References
  1. "Natural Resources Canada-Canadian Geographical Names (Assiniboine River)". Retrieved 2014-08-29.
  2. "Atlas of Canada Toporama". Retrieved 2014-08-29.
  3. R. Douglas, Place names of Manitoba, Geographic Board of Canada, Department of Interior, Canada, 1933
  4. Atlas of Canada. "Rivers of Canada". Archived from the original on January 25, 2008. Retrieved 2008-02-15.
  5. Natural Resources Canada. "The Assiniboine River bursts its banks". Archived from the original on 3 February 2008. Retrieved 2008-02-15.
  6. (CTV)
  7. (The Canadian Press)
  8. (CJOB 68) Archived March 31, 2012, at the Wayback Machine
  9. "2011 Flood: Technical Review of Lake Manitoba, Lake St. Martin and Assiniboine River Water Levels" (PDF). Province of Manitoba. October 2013. p. 25. Retrieved July 25, 2015.
  10. "MARCH OUTLOOK REPORT FOR MANITOBA March 23, 2018" (PDF). Province of Manitoba. March 23, 2018. Retrieved March 31, 2018.
  11. "Daily Water Levels and Forecasts Assiniboine River June 22, 2012" (PDF). Province of Manitoba. 2012. Retrieved July 25, 2015.
  12. "Summer Flood Bulletin #15". Province of Manitoba. July 10, 2014.
  13. "Flood Report For Manitoba - July 12, 2014" (PDF). Province of Manitoba. July 12, 2014.
  14. "Flood Report For Manitoba - April 11, 2017" (PDF). Province of Manitoba. April 11, 2017.
  15. "Daily Flood Sheet - April 17, 2017" (PDF). Province of Manitoba. April 17, 2017. Archived from the original (PDF) on April 18, 2017. Retrieved August 24, 2017.
  16. "Red River Floodway Operation Report Spring 2017" (PDF). Province of Manitoba. June 29, 2017.
  17. "MARCH OUTLOOK REPORT FOR MANITOBA March 23, 2018" (PDF). Province of Manitoba. March 23, 2018. Retrieved March 31, 2018.
  18. "Red River Floodway Operation Report Spring 2017" (PDF). Province of Manitoba. June 29, 2017.
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