Media Bulletin - Manitoba
March 26, 2013
PROVINCE ISSUES MARCH FLOOD OUTLOOK
– – –Increased Risk for Red, Souris, Pembina, Assiniboine, Saskatchewan, Qu-Appelle Rivers and in Interlake, but still Lower than 2011 for all Rivers Except the Red
The Manitoba Infrastructure and Transportation Hydrologic Forecast Centre’s second 2013 flood outlook calls for increased spring flooding potential on the Red, Souris, Pembina, Assiniboine, Saskatchewan and Qu’Appelle rivers, and in the Interlake, due to additional March snowfall, above‑average snowpack with high water content in many parts of the province, and low temperatures that are keeping frost in the ground longer than normal.
Provincial forecasters say, while these conditions have increased the risk of flooding to moderate to major, up from minor to moderate as forecast earlier this year, the current outlook does not foresee prolonged river flooding and high lake levels as in 2011. The outlook has trended towards the 2009 flood in the Red River Valley and the Interlake.
In addition to heavier-than-average snowfall, which was 200 per cent of normal in much of Manitoba, Saskatchewan and North Dakota this month, provincial forecasters have concluded that cooler‑than‑normal temperatures have increased the depth to which soil remains frozen. Across southern Manitoba, soil is frozen to a depth of between 50 centimetres (1.5 feet) to more than 100 cm (three ft.), mainly due to prolonged periods of very cold temperatures. Frozen soil does not absorb meltwater as easily as thawed soils, and it can increase spring run-off and overland flooding.
The colder-than-normal temperatures will also cause a later spring melt, which increases the likelihood of a rapid melt. Cool temperatures later into the year also increase the likelihood that the melting snowpack and normal spring rains will occur at the same time.
While all these factors have increased the risk of flooding to moderate to major, conditions can change quickly and the outlook is still very dependent on weather conditions from now until the spring melt.
Lake Level and River Flow Conditions
Major rivers have thicker-than-normal ice cover with flows either below or close to normal for this time of year. Overall, river flows are below those of February 2011.
At the time of freeze-up, water levels for the Red, Assiniboine, Souris, Qu’Appelle and Winnipeg rivers were below normal. The Saskatchewan River at The Pas is above normal, but lower than it was going into the 2011 flood.
The Assiniboine River is high for this time of year due to controlled releases from the Shellmouth reservoir, which have brought the reservoir down to near-record low levels to accommodate potential high water flow from Saskatchewan’s above-average snowpack. In the Interlake, the Waterhen and Fairford river flows are above normal due to the consistently high water level of Lake Winnipegosis.
Water levels for lakes Winnipegosis, Manitoba and Winnipeg are all well below the levels going into the 2011 flood. Lake Manitoba is down to its current level of 811.8 ft. above sea level, which is within its operating range of 810.5 to 812.5 ft. and below its historical long-term average level of 812.12 ft. Lake St. Martin is presently at 801 ft. with flood protection levels at 806 ft.
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Updated: 12:34 PM GMT on March 29, 2013
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