Winnipeg Free Press - PRINT EDITION

Where all that water is going -- and how

  • Print

As the flood of 2011 spreads across more of Manitoba, Winnipeggers may wonder how the provincial capital remains so high and dry.

The answer involves the co-ordinated use of three flood-mitigation measures completed four decades ago: The Red River Floodway east of Winnipeg, the Portage Diversion west of Portage la Prairie and the Shellmouth Dam and Reservoir north of Russell.

Thanks to all three, the flood threat for Winnipeg actually subsided on Monday, as flows on the Assiniboine River within the city subsided by approximately 40 per cent since Sunday and flows on the Red River remained static within the city.

Here's how the flood-mitigation measures work:

Red River Floodway

Completed: 1968 for $63 million; expansion completed in 2009 for $665 million.

How it works: The floodway diverts part of the Red River's flow at Winnipeg around the east side of the city through a channel that re-enters the river at Lockport. A control structure at the Courchaine Bridge in St. Norbert allows gates to be raised, forcing water over a spillway and into the diversion channel.

Flood mitigation: The expanded floodway can handle 140,000 cubic feet of water per second (CFS), which is roughly equal to the entire flow of the Red River south of Winnipeg at the peak of the 1997 "Flood of the Century."

On Monday: The Red's flow was 59,000 cubic feet per second south of Winnipeg. Of that, 23,000 CFS was diverted into the floodway while the remaining 36,000 CFS entered Winnipeg.

Portage Diversion

Completed: 1970 for $20.5 million

How it works: The diversion sends part of the Assiniboine River's flow southwest of Portage la Prairie north to Lake Manitoba instead of allowing it to continue east toward the Red River at Winnipeg.

Flood mitigation: As much as 25,000 cubic feet per second can be diverted to Lake Manitoba.

On Monday: The Assiniboine's flow was 26,400 cubic feet per second west of Portage la Prairie. Of that, 20,300 CFS was diverted to Lake Manitoba, with the remaining 6,100 CFS flowing toward Winnipeg.

 

Shellmouth Dam & Reservoir

Completed: 1972 for $10.8 million

How it works: The Shellmouth Dam on the Assiniboine River can hold back flows from the upper Assiniboine drainage area, most of which sits inside Saskatchewan. The resulting man-made lake is called Lake of the Prairies. Manitoba Water Stewardship draws down the reservoir before floods to create more capacity in the reservoir, which is designed to spill over the lip of the dam when the lake level reaches 1,408.5 feet above sea level.

Flood mitigation: The reservoir can hold back most of the Assiniboine River's flow until it fills. Typically, 400 CFS is released at all times.

On Monday: Approximately 6,560 CFS was flowing into the reservoir, with 480 CFS being released downstream. Lake of the Prairies rose to 1,390.4 feet above sea level.

 

-- Bartley Kives

More at winnipegfreepress.com

-- FLOOD CAMS: Check out our nine live river cameras

-- MAP: See flooding trouble spots, and add your own

-- YOUR VIEW: Reader-submitted flood photos

-- VIDEO: Flood update and Flood danger demo

Republished from the Winnipeg Free Press print edition April 19, 2011 A7

Fact Check

Fact Check

Have you found an error, or know of something we’ve missed in one of our stories?
Please use the form below and let us know.

* Required
  • Please post the headline of the story or the title of the video with the error.

  • Please post exactly what was wrong with the story.

  • Please indicate your source for the correct information.

  • Yes

    No

  • This will only be used to contact you if we have a question about your submission, it will not be used to identify you or be published.

  • Cancel

Having problems with the form?

Contact Us Directly
  • Print

You can comment on most stories on winnipegfreepress.com. You can also agree or disagree with other comments. All you need to do is be a Winnipeg Free Press print or e-edition subscriber to join the conversation and give your feedback.

You can comment on most stories on winnipegfreepress.com. You can also agree or disagree with other comments. All you need to do is be a Winnipeg Free Press print or e-edition subscriber to join the conversation and give your feedback.

Have Your Say

New to commenting? Check out our Frequently Asked Questions.

Have Your Say

Comments are open to Winnipeg Free Press print or e-edition subscribers only. why?

Have Your Say

Comments are open to Winnipeg Free Press Subscribers only. why?

The Winnipeg Free Press does not necessarily endorse any of the views posted. By submitting your comment, you agree to our Terms and Conditions. These terms were revised effective April 16, 2010.

letters

Make text: Larger | Smaller

Poll

Do you think e-cigarettes should be banned by the school division?

View Results