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Flood Forecast, 2007
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Flood Forecast, 2007
 

To forecast spring flood conditions, provincial flood forecasters examine what the weather could be like for the next three months.

Forecasters take statistics from the past 40 years on snowfall, melt rates and spring rain and superimpose them on top of present condition in the river basins. The terms "favourable," "average," and "unfavourable" are used to describe weather conditions that could happen from now until April.

Provincial officials say there is a 10-per-cent chance of the weather being favourable or better, and a 10-per-cent chance of unfavourable or worse.

In general, "favourable conditions" mean a very slow melt, a gradual breakup of ice, and dry weather. "Unfavourable" conditions include a rapid melt with above-average precipitation.

The flood forecasts below were issued by the province on March 23, 2007, based on conditions around the province up to that point.

Red River Watershed

Favourable weather:

No flooding expected on main stem or tributaries.

Average weather:

Red River expected to remain within its banks; only minor operation of the Red River Floodway.

Flooding not expected on tributaries, including the Pembina River.

Unfavourable weather:

Minor over-bank flows possible from Emerson to just south of Morris. Operation of the floodway would keep the crest in Winnipeg below 17.5 feet (5.3 metres). Construction on the floodway channel would not interfere with floodway operation.

Minor flooding on tributaries.

Assiniboine River Watershed

Favourable weather:

No flooding on the Assiniboine or its tributaries.

Operation of the Portage Diversion not likely.

No flooding along tributaries.

Average weather:

Shellmouth Reservoir successfully stores spring inflows; minor operation of the Portage Diversion prevents flooding from Portage la Prairie to Winnipeg.

Minor over-bank flows from St. Lazare to Griswold during April. No flooding expected downstream of Brandon.

Flooding not expected on tributaries.

Unfavourable weather:

Significant flooding along the Assiniboine River from Shellmouth to Brandon, with crests similar to those in 2006.

Flooding expected to end before mid-May at all locations unless very heavy precipitation, similar to that of 2006, develops over the basin upstream of Brandon..

Operation of Portage Diversion would prevent flooding from Portage la Prairie to Winnipeg.

Flooding could occur along the Qu’Appelle River, the Shell River and Scissor Creek near McCauley.

Souris River Watershed

Favourable weather:

Flooding not expected.

Average weather:

Little or no flooding expected.

Unfavourable weather:

Minor flooding from Coulter to Melita along main stem, similar to that of 2006.

Minor localized flooding of tributaries possible.

Interlake Region

Favourable weather:

Flooding not expected .

Average weather:

Streams experience little or no flooding.  

Flooding adjacent to the Shoal Lakes, which is ongoing, would spread somewhat.

Unfavourable weather:

Near bank-full flows possible on the Fisher River including Peguis townsite.  

Other streams would likely remain within their banks unless ice jams develop.

Flooding of agricultural lands near the Shoal Lakes increases significantly.

With unfavourable weather, peak flows in the Fairford and Dauphin rivers would be similar to those of 2006 when levels were high but flooding was avoided during the ice-free period.

Eastern Region

Favourable weather:

Flooding not expected; concern about low lake levels in southeastern Manitoba including the Whiteshell.

Average weather:

Flooding not expected.

Unfavourable weather:

Flooding not expected.

Westlake-Dauphin-The Pas Region

Favourable weather:

Flooding not expected on the Whitemud River and its tributaries or on streams flowing into Dauphin Lake.

Minor flooding on most streams from the Fork River north to the Saskatchewan River, but much less than during the spring of 2006.

Average weather:

Flooding not expected on the Whitemud River and its tributaries nor on streams flowing into Dauphin Lake, with possible exception of the Big Grass River.

On the Red Deer River, flood potential remains high but is not as high as in 2006. Inflow to Red Deer Lake will be only half of the extreme value observed in 2006, but the river would be at the top of its banks.

Swan River crests 15 to 30 centimetres lower than 2006, when flooding in the community of Swan River was narrowly avoided.

Crest on the Carrot River slightly lower than spring of 2006. Diking at Opaskwayak Cree Nation likely.

Crest on Saskatchewan River expected to be slightly lower than 2006 at The Pas.

Flooding of the Saskeram area on the Pasquia River southwest of The Pas likely to occur again this spring with levels similar to those of 2006.

Potential for flooding on streams flowing off Duck Mountain and Porcupine Mountain, especially if especially if a rapid melt occurs resulting from daytime temperatures of 15 Cto 20 C and strong winds and rain develop.

Unfavourable weather:

Flooding on the Whitemud River, but less than 2006.

Minor flooding on streams in the region, especially if there is a rapid melt in the high terrain of Riding Mountain.

Less inflow from Red Deer River into Red Deer Lake than in 2006, but significant over-bank flows.

Swan River crests similar to 2006.

Crest on Carrot River at near-record highs west of The Pas, about 15 cm higher than 2006. Diking necessary at Opaskwayak Cree Nation.

Crest on Saskatchewan River at The Pas could crest exceed crest observed in spring 2006.

Flooding of the Saskeram area on the Pasquia River southwest of The Pas likely to occur again this spring with levels similar to those of 2006.  

Potential for flooding on streams flowing off Duck Mountain and Porcupine Mountain, especially if especially if a rapid melt occurs resulting from daytime temperatures of 15 Cto 20 C and strong winds and rain develop.


Northern Manitoba:

 

Run-off north of latitude 54 generaly expected to be above average.

Flooding unlikely on the Churchill or Nelson rivesr.  


Lake Forecast

 

Lake Winnipeg: Low this year due to dry conditions last summer.  A smaller-than-usual rise is likely this spring due to below-average inflows from the Winnipeg and Red rivers.  

With average weather conditions, the lake may rise to little more than 713 feet by early summer, which is about one foot lower than average.

Lake Winnipegosis: likely to rise to last year’s levels even with average weather conditions.  Flooding of low-lying agricultural lands adjacent to the lake is expected again this year.

Lake Manitoba: somewhat lower than in 2006 unless the unfavourable weather conditions develop. Expected to remain within the operating range of 710.5 and 712.5 feet.  

Lake St. Martin: expected to be at well-above-average levels but somewhat lower than last year.

Lake of the Woods and other Whiteshell lake, including those on the Winnipeg River system: likely to be low again in 2007 unless precipitation is above average from now through May 2007.

Most lakes in southwestern and western Manitoba are at somewhat below-average levels due to dry weather last summer. Most are expected to rise to near-normal levels by the end of spring run-off.

Lakes in the vicinity of The Pas are at above-average levels and are likely to rise higher than desirable this spring.  Last spring’s flooding of low-lying lands near these lakes is likely to be repeated this spring.

The level of Reindeer Lake and most other lakes in far northern Manitoba are expected to be at average or above-average levels after 2007 spring run-off.

 

Source: Province of Manitobaa


Last Updated: Feb. 27, 2007
Web Journalist: Wendy Sawatzky
Telephone: (204) 788-3646
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