PROVINCE ADVISES FLOODING MAY EXTEND ALONG UPPER ASSINIBOINE RIVER TO MILLWOOD AREA
Manitoba Infrastructure and Transportation advises a flood watch has been issued for low-lying agricultural areas along the Assiniboine River in the Millwood area. The lower Assiniboine is expected to remain within its banks.
A flood warning remains in effect for the Assiniboine River Valley immediately downstream of the Shellmouth Reservoir including the Shellmouth Bridge.
The Hydrologic Forecast Centre of Manitoba Infrastructure and Transportation reports river levels immediately downstream of the dam are exceeding flood stage. Further downstream, the river is expected to start rising, approaching flood stage as spillway outflow increases.
Portions of the upper Assiniboine River are experiencing wet conditions as a result of significant storms which produced double the normal precipitation in the months of April, May and June. Due to the wet soil conditions, additional rainfall will result in increased reservoir inflows and levels.
Little rainfall of up to five millimetres (mm) has been reported in the last 24 hours in the upper Assiniboine basin. Precipitation amounts of up to 15 mm are forecast over the upper Assiniboine and in southern Manitoba in the next three days. However, these forecast amounts are uncertain at this point.
Manitoba Infrastructure and Transportation is monitoring weather across Saskatchewan and southern Manitoba, and will provide updates as conditions evolve.
River Flow Conditions and Shellmouth Reservoir Operations:
The Shellmouth Reservoir level is at 1,410.93 feet (ft.), a rise of one-third of a foot in the last 24 hours. This level is 2.4 ft. above the spillway elevation. The inflow is 4,500 cubic feet per second (cfs). The Shellmouth gates are closed and, as a result, the conduit outflow is zero. The spillway outflow is 2,500 cfs.
Above bank-full flows will continue to affect areas immediately downstream of the dam including the Shellmouth Bridge and Millwood area. The flows of the Assiniboine River at Kamsack, Sask., and the Shell River at Inglis are 2,680 cfs and 460 cfs respectively. The river flow near Miniota is 3,900 cfs and near Brandon is at 3,970 cfs. The Qu’Appelle River flow at Welby is 1,700 cfs. Assiniboine tributaries are generally declining after seeing minor peaks. Further rises may occur if significant rains fall in the next few days.
The operation strategy for the reservoir is continually reviewed with the Shellmouth Reservoir Regulation Liaison Committee, which has representation from municipalities and conservation districts, on the reservoir and area downstream of the Shellmouth Reservoir. Water level conditions of the dam are provided daily to the committee members.