PROVINCE ADVISES OUTFLOWS INCREASED FROM SHELLMOUTH RESERVOIR TO MAKE ROOM FOR FORECASTED RUNOFF

The Hydrologic Forecast Centre of Manitoba Infrastructure and Transportation advises that based on latest inflow forecasts, outflows from the Shellmouth Reservoir will be increased down the Assiniboine River to better manage reservoir water levels.

April 21, 2016 – Outflow from the dam will be increased tomorrow from the present flow of approximately 1,900 cubic feet per second (cfs) in two stages up to 3,000 cfs.  This will result in a water level increase of about two to three feet between the Shellmouth Dam and St. Lazare.  This may be affected by other streams that flow into the Assiniboine River downstream of the dam.  The higher outflows will result in some overbank flooding along the upper Assiniboine River and will result in some flooding of agricultural land between the reservoir and St. Lazare.
Based on current forecasted weather conditions, the highest water level between the dam and Brandon is expected in the first week of May.

Without the dam, flows on the Assiniboine River in the vicinity of the dam would be significantly higher at approximately 10,300 cfs.

The operating guidelines for Shellmouth Dam and Reservoir call for outflows to be increased to keep water levels from exceeding the top of the reservoir spillway.  Higher outflows now will slow the rate at which the reservoir water level is rising and preserve storage space on the reservoir for the growing season.  The additional space also allows the dam and reservoir to be used to capture runoff from summer storms and to prevent potential flooding later in the year during the growing season.

The Shellmouth Dam and Reservoir are operated in consultation with the Shellmouth Reservoir Regulation Liaison Committee.  The committee has been meeting on a regular basis to discuss and advise on operations.