Hey there, time traveller!
This article was published 2/11/2014 (2317 days ago), so information in it may no longer be current.
The province is considering building a major retention dam on the Assiniboine River, larger than the Shellmouth Dam that created Lake of the Prairies.
A provincial spokesman confirmed engineering company KGS Group is studying a host of options for reducing the volume of water in the Assiniboine and Lake Manitoba, including a very large dam, to fortify the province's flood defence.
The dam would be either west of Brandon, at Alexander, or southwest of Portage la Prairie, near Holland. The one being considered at Alexander would easily be the largest retention dam in Manitoba, creating a reservoir three times the size of Lake of the Prairies.
This is the second study by KGS as part of the province's flood-mitigation efforts. The first study, already released, looked at improving drainage from Lake Manitoba via a new drainage channel, in addition to the existing Fairford River outlet. Various options proposed will cost up to $500 million.
The second study, which includes dams upstream on the Assiniboine River, looks at what can be done to the feeder system into Assiniboine and Lake Manitoba to ease flooding, the provincial spokesman said. The second study is expected to be released in November, with open houses for public input held in December.
A dam at Alexander would create a reservoir nearly 100 kilometres long between the towns of Alexander and Miniota, said Stan Cochrane, president of the Assiniboine Valley Producers Association. It would reduce the flow in the Assiniboine River during flood years by about 30 per cent, he said. The producers association met with KGS several times during preparation of the study and was privy to some of its information. KGS refused to comment.
If the Alexander dam is built, "you could call me in Hawaii," Cochrane said, because the government would have to expropriate his farm, plus thousands more acres of cropland. Cochrane said he'd almost welcome it as his farm fields, west of Brandon, have been flooded four times in the last five years by the Assiniboine River.
While such a mammoth project seems almost inconceivable due to the cost and environmental considerations, people close to the study say the dynamics have changed after the Lake Manitoba floods in 2011 and 2014. Due to greater frequency of flooding, what was once considered a one-in-300-year flood is now viewed more like a one-in-100-year flood.
That changes the cost-benefit ratio dramatically. The study will show cost-benefit ratios for the various options.
The study also looks at building a dam near Holland, but one considerably smaller, said Lorne Henry, who farms on both sides of the Portage Diversion, and who has also been privy to information in the KGS study. A Holland dam would also hold back less water. Henry said both Alexander and Holland dams were studied back in the 1960s, along with the Winnipeg floodway and Portage Diversion, but were considered too costly at the time.
Another option being considered is to build a series of smaller dams on the 20 or 30 tributaries that empty into the Assiniboine and Souris rivers. Smaller dams are considered less disruptive to the environment and might be more palatable to environmental groups. However, they would reduce the floodwaters by just 10 per cent, Cochrane said.
The study will also look at shoring up dikes along the Assiniboine River from Portage la Prairie to Winnipeg. In 1976, a massive construction effort, which included the military, built up those dikes in two weeks. As a result, that stretch of the Assiniboine was able to carry 26,000 cubic feet per second.
However, in the 2011 and 2014 floods, only 18,000 cfs were allowed down that part of the Assiniboine. As a result, the Portage Diversion had to reroute 34,000 cfs of water over several months into Lake Manitoba, while the Fairford channel's capacity was just 15,000 cfs.
The study also looks at individual retention ponds on farm fields. That may be the most practical from a cost and environmental standpoint.
The study even looked at expanding the Portage Diversion. That would presumably be contingent on the government choosing the largest and most expensive channel option for Lake Manitoba capable of draining 15,000 cfs.
Cochrane is pessimistic anything will get done. "Once they dig that ditch between Lake Manitoba and Lake Winnipeg, they won't have five cents left to get anything else done," he maintained.