Public cautioned to stay out of Missouri River bed during drawdown

On Sept. 25, NorthWestern Energy will begin drawing down Rainbow Reservoir about 11 feet from the current full-pool level to replace wooden flash boards on the face of the dam.

The wooden flash boards were last replaced in 2004, according to NorthWestern Energy, and the aged boards are leaking water, requiring a high level of maintenance and frequent repairs. Replacing the boards will reduce maintenance and make the dam perform more efficiently.

The reservoir water drawdown begins Sept. 25 and for the following five days, the construction project will remove and replace the old boards.

The reservoir will be back to full pool by Oct. 6.

People and pet should not enter the riverbed. Deep mud, slippery rocks and the short duration of the water drawdown will create safety hazards, according to Montana Fish, Wildlife and Parks.