May 27, 2010
Rains Causing Increased River Levels in Parts of Manitoba
Manitoba Water Stewardship advises that two storms on the long weekend produced widespread rain over most of Manitoba, Saskatchewan, North Dakota and Minnesota. Most areas received 20 to 40 millimetres (0.8 to 1.6 inches) with some areas east of the Red River near the U.S. border, in the RMs of Franklin, Stuartburn and Piney receiving 75 to 100 mm (three to 3.9 in.). Heavy rain fell in the U.S. portion of the Red River watershed, mainly north of Grand Forks, with up to 125 mm (4.9 in.) in some areas.
Another storm is forecast to affect Manitoba and parts of the U.S. from today through next Monday with 25 to 40 mm (one to 1.6 in.) of rain predicted to fall in many areas with higher amounts possible where thundershowers develop.
Run-off has been very significant in the U.S. portion of the Red River and the Roseau River watershed. Elsewhere run-off has been generally minor. Run-off from the next storm will be more significant in many areas due to the wet soil conditions resulting from recent rains.
A crest on the Red River is developing in the U. S. due to heavy run-off in the Red Lake River watershed and points north to the Roseau River. Additional rises in the Manitoba portion from this morning will range from 2.1 metres (seven feet) at Emerson to about 1.5 m (five ft.) from Morris to the floodway inlet and less than 0.9 m (three ft.) from Winnipeg to Selkirk. Crests are expected at Emerson on June 4, Ste. Agathe June 6, the floodway inlet June 7, downtown Winnipeg (James Avenue) June 8 and Selkirk on June 9. The river will remain well within its banks in southern Manitoba. Although these river rises do not include the effects of the next storm expected later this week, forecasts will be updated once rainfall amounts from that storm are available.
On the Assiniboine River, the outflow from the Shellmouth Reservoir was increased to 1,000 cubic feet per second on May 23 due to concerns about excessive reservoir levels. A further increase may be necessary to guard against additional run-off from the storm expected later this week. River levels have increased by about 1.4 m (4.5 ft.) at Shellmouth recently and may increase to near bankfull by the end of May if the next storm develops as forecast. Additional rises in levels from St. Lazare to Winnipeg will be less than 0.6 m (two ft.) based on no further precipitation for the next few weeks but rises could be substantially more if the next rainstorm develops as expected.
Levels of the Souris River will decline somewhat due to recent reductions in releases from the J. Clarke Salyer Refuges in North Dakota. Some rises could develop following the next storm but flooding of low-lying haylands in the Coulter area is unlikely to exceed what occurred earlier this month.
Levels on the Roseau River have risen close to one metre (3.3 ft.) at Dominion City but the river appears to be cresting at this location due to local run-off. Run-off from the U. S. portion will cause a gradual rise from Caribou to Stuartburn during the next two weeks, but the river is expected to remain well within its banks. It is possible that flooding could develop in June if the storm later this week produces heavy rain as presently predicted.
Rivers in the Interlake, Westman and The Pas regions are rising slowly from last weekend’s rain. It is possible minor flooding could develop in the Westman region May 29 and 30 if rain from the next storm falls as forecasted.
The latest information on water levels and outlook reports is available at www.gov.mb.ca/waterstewardship/.
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