Flood warnings are in effect for streams and rivers on the Assiniboine River and all points downstream of the Shellmouth Dam. Warnings also include the Dauphin Lake Basin, streams and rivers east of the Duck Mountains, the Souris River from Melita and all downstream reaches, Pipestone Creek (all reaches), Oak Lake and Plum Lakes, Plum Creek to the Souris River (including the town of Souris), and the Qu`Appelle River in St-Lazare area.
High water advisory is in effect for all major lakes in Manitoba and the community of Red Deer Lake.
A three-day unstable weather system is expected to bring widespread rain ranging from 20 to 50 millimetres across the entire southern Manitoba watershed. Due to recent rain, soils have a reduced capacity to retain water and any further rain will likely run off into streams and rivers.
Communities along the Assiniboine River between Portage la Prairie and Headingley are advised that water levels along the river will be increasing in approximately two to four days. The unprecedented flows are a result of last week’s weekend storm, the timing of the melt from the storm and additional rainfall forecast for this week.
The Manitoba government has requested military assistance from the Government of Canada to assist with urgent work required to raise the dikes along the Assiniboine River between Portage la Prairie and Headingley. Additional manpower is needed to sandbag low areas of the provincial earthen dike and raise private dikes an additional two feet over the level recommended on Friday in the rural municipalities of Cartier, St. Francois Xavier and Headingley. Approximately 2.7 million sandbags from the provincial stock and from the City of Winnipeg stock will be deployed.
Flows on the Assiniboine River are forecast to increase to 50,000 cfs at the Portage Diversion in approximately two to four days. This inflow forecast is under review and will be revised based on upcoming rain. Flows in the Portage Diversion will be increased to provide as much protection as possible to the river east of Portage la Prairie. With the forecast rain, water levels will increase approximately 0.5 to 0.8 ft. from local run-off in the Assiniboine River downstream of Portage la Prairie.
Assiniboine River
Water levels on the Shellmouth Reservoir have decreased by 0.02 ft. since yesterday to 1,414.42 ft. Inflow into the Shellmouth Reservoir is approximately 11,800 cfs. The Shellmouth Dam will be operated to maintain outflows at 12,000 cfs today.
St-Lazare’s water levels have increased 0.02 ft. since yesterday to 1,292.58 ft. St-Lazare’s community flood protection level is 1,294.4 ft., providing approximately 2.7 ft. of freeboard at current water levels.
Water levels at Sioux Valley were measured late yesterday afternoon at 1,204.08 ft., with a forecast peak between 1,204.7 and 1,205.2 ft. Dikes at the Sioux Valley First Nation will provide flood protection to 1,207 ft.
Water levels on the Assiniboine River at the First Street Bridge in Brandon are 1,182.17 ft., an increase of 0.87 ft. since yesterday. Flows at the First Street Bridge in Brandon were 37,500 cfs this afternoon. Without the Shellmouth Reservoir, water levels at Brandon would be three ft. higher. Natural flows on the Assiniboine River at Brandon today would be comparable to the 1882 flood without the benefits provided by the reservoir.
Peak water levels and dates have been reassessed for the Brandon area to account for forecast rains. Forecasters are estimating that water levels will peak between 1,182.5 and 1,183.0 ft., however, these numbers will be updated with any changes from forecast rain. Dikes are being raised to provide adequate freeboard at the upper end of the forecast range.
Flows in the Portage Diversion channel this morning were at 20,000 cfs. Inflow upstream of Portage la Prairie is 38,000 cfs. Flows on the Assiniboine River at the diversion were 18,000 cfs this morning.
A flood warning has been issued for the Assiniboine River and all points downstream.
Souris River
Water levels at Melita are 1,410.29 ft. today, a decrease of 0.07 ft. since yesterday.
If the forecast rains occur, water levels on the Souris River are expected to rise. Forecasters are assessing whether this new peak will be greater than previous levels.
The Pipestone Creek is nearing a second crest, slightly lower than the previous crest. Water levels in Oak Lake have increased to 1,412.11 ft., an increase of 0.23 ft. over the last two days.
The Souris River at Wawanesa reached 14,350 cfs today.
Red River
Water levels just upstream of the Red River Floodway inlet are 763.75 ft., with flows of 72,600 cfs. Flows in the floodway are approximately 33,300 cfs.
Water levels on the Red River at James Avenue in Winnipeg have decreased 0.06 ft. to 19.55 ft. Water levels are expected to remain high for an extended period of time. Flows at James Avenue this morning were approximately 58,600 cfs.
Other Major Waterways
The flood warning for Dauphin Lake and all inflowing tributaries remains in effect.
The flood warning for streams influenced by snowmelt in the Duck Mountains within the Lake Winnipegosis Basin remains in effect.
Lakes
Maps indicating wind-eliminated inundation areas around the south basin of Lake Manitoba are available on the Manitoba Water Stewardship website and have been provided to the rural municipalities surrounding the lake to help land owners prepare for high water levels. It is advisable the public make flood preparations that account for these forecasted high water levels.
Water levels on Red Deer Lake are forecast to reach flood stage. A high water advisory has been issued for the community of Red Deer Lake. It is advisable that the community make necessary flood preparations.
Outflows from Lake Manitoba were estimated at 14,300 cfs as of late yesterday. This flow value will be assessed later today.
Forecasters have estimated peak wind-eliminated water levels for Lake Manitoba and Lake St. Martin are both likely to reach high water levels that are unprecedented since regulation of the lakes began in 1961. These forecast elevations are preliminary at this time and may be revised with major weather changes and as computer models are refined.
Open water is visible on the lower half of Lake Winnipeg’s south basin. The risk of shoreline ice pile up today is low on all assessed lakes.
For more information, please see www.manitoba.ca/flooding and find the most up-to-date highway information at www.gov.mb.ca/mit/roadinfo or 1-877-MBRoads (1-877-627-6237) and on Twitter by following @MBGov.
