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Manitoba Water Stewardship

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Condition Reports

Assiniboine River & Shellmouth Reservoir Operation Update

August 30, 2007

Shellmouth Reservoir conditions - August 30, 2007

Level    -    1403.3 feet (near the desired summer level).

Outflow    -    changed from 800 cfs to 450 cfs today (Aug 30).

Inflow    -    approximately 130 cfs and falling.

Proposed Operation---The outflow will be further decreased to 250 cfs on Sept. 6 and to 100 cfs on Sept. 13. The gradual decrease is being done to reduce the chance of bank slumping along the Assiniboine River. The outflow will remain at 100 cfs until mid November at which time the winter drawdown will commence. The reservoir water level will decline slowly to 1402.5 feet by September 13. As usual, levels and operations could deviate from the plan if unusual weather conditions develop. Comments on the operation plan are invited from stakeholders along the Assiniboine River and Shellmouth Reservoir.

Fishing Lake Outflows---Saskatchewan Water Authority has advised that there will be no augmented outflow from Fishing Lake, apparently due to protests from native bands in the area. Construction of the ditch has been halted. The outflow from the lake is presently about 50 cfs and this is expected to gradually decline to zero by freeze-up.
 

Assiniboine River

The river level at Shellmouth has declined 2.5 feet during the past two weeks. It will decline another foot by tomorrow, an additional foot Sept 6-7 and another foot Sept 13-14.

River levels downstream will continue to decline significantly unless heavy precipitation develops. The declines will be progressively less than at Shellmouth as one goes downstream, dropping to about half as much by the time they reach Headingley. The time of travel for these conditions is about 5 days to Brandon, 8 days to Portage la Prairie and 10 days to Headingley.

Assiniboine River flows have been at or above the upper decile (1:10) condition during August but are expected to gradually decline to near median values during September based on normal weather conditions from now on.

Other Rivers:  Note that weekly river flows continue to be posted on our web site every Friday. Just click on this address. There are two data tables at the bottom of the page in case you find the charts difficult to read.