Manitoba Water Stewardship reports that a storm crossing the Dakotas will bring 20 to 40 millimetres (0.8 to 1.6 inches) of rain to the U.S. portion of the Red River watershed today and tomorrow. Southeastern Manitoba, including the city of Winnipeg, is expected to receive 10 to 20 mm (0.4 to 0.8 in.). There is also a small chance of thundershowers that could produce heavier amounts locally in some areas.
The Red River level in downtown Winnipeg had declined to 5.12 m (16.78 ft.) as of this morning and will remain in the range of 4.9 to 5.2 m (16 to 17 ft.) for most of this week. When river levels are in these high ranges, the normal capacity of the city’s sewer system is reduced. If heavy rain develops, there is an increased risk of overloaded sewers backing up through house sewer lines and flowing into basements that are not protected.
Although the rain forecasted for the next few days is unlikely to cause sewer backup, there is still a risk of basement flooding if a thunderstorm with heavy rain were to develop. The extent of possible basement flooding from a heavy rainstorm would depend on the amount and intensity of the rain.
The City of Winnipeg has advised homeowners to take steps to protect their homes from basement flooding. This includes installing a sewer line backup valve and a sump pit with pump in basements to ensure maximum protection.
The Portage Diversion has been used to reduce flows on the Assiniboine River as much as possible and lower river levels in Winnipeg to reduce the potential for basement flooding. The floodway gates will also continue to be operated to provide maximum benefit to Winnipeg while still maintaining below-natural levels south of the floodway inlet.
