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Painted Rocks Reservoir back in action after spillway shutoffs

 

By Michael Howell

Irrigators and recreationists are all happy that water is once again spilling over the dam at Painted Rocks Reservoir. Flows from the dam were incrementally reduced and then shut down for repairs at the end of April. As a result, a stretch of the West Fork of the Bitterroot just below the dam was essentially dewatered until receiving input from springs and streams further down.

Painted Rocks Reservoir was built in 1938. The reservoir captures about 32,656 acre feet of water to be used by both irrigators and recreationists. 10,000 acre feet is leased to the Painted Rocks Reservoir Association for irrigation and 15,000 acre feet is leased to the Montana Department of Fish, Wildlife and Parks for instream flows to protect the fishery in the Bitterroot River. The river flows are chronically low in the mid valley in late summer and the FWP water is released to supplement those flows.

There was some concern about fish dying during the repair process due to lack of water flows when photos of a few dead fish were placed on the internet. According to DNRC water specialist Larry Shock, some mortality among the fish population is expected when the water is shut off at the dam. He said every effort was made to minimize the impact upon the fishery by staging the flow reductions so that fish would have a chance to migrate into pools. He said the photos of dead fish that he saw were taken just below the dam where the effects of the shutdown are most severe. Further downstream springs and streams begin contributing to the flow once again.

The first reduction in flows took place on Friday, April 26. Further reductions took place on Monday, April 29, and the final shutoff came on April 30. Shock said that in consultation with FWP officials it was decided to limit the shutdowns to four hours. On Wednesday, May 1, it was shut off for another four hours and then again for a few hours on Thursday, May 2.

Shock said the purpose of the shutdown was two-fold. The seals on the head gates at the dam needed to be adjusted and some concrete repairs made inside the discharge tunnel. Not all the concrete repairs were completed due to the short time frame. Tentatively, the plan is to do the remaining repairs in the fall when the dam is shut down for its annual inspection.

The good news for everyone is that the ordeal is over and water from a full reservoir began spilling over the dam last Saturday evening.

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