A rescue operation in the Upper Deschutes is planned for this weekend — but it’s not the kind involving distressed kayakers, boaters or swimmers. In need of help are trout, kokanee, sculpin and other fish that will soon be left high and dry in channels connected to the river, due to a seasonal river level fluctuations.

With Wickiup Reservoir at just 11% full, the transition from summer to autumn means slowing down the outflow of water from the reservoir into the Deschutes. This preserves water for farmers to use during the next growing season. As the outflow slows, the water level drops, creating pockets of isolated water in the side channels. As the pools dry out, the fish die en masse.

Conservation groups and volunteers coordinate with the irrigation districts to rescue the fish just as the water flows are dialed back. This year, that operation is expected to take place Saturday.

In fall, the outflow from Wickiup Reservoir is reduced to 100 cubic feet per second by Oregon Water Resources Department. The channels running off the Deschutes require 130 to 180 cubic feet per second to stay filled with water, according to Craig Horrell, managing director of the Central Oregon Irrigation District. At 100 cubic feet per second, fish get trapped in small pools and face certain death unless they are moved.

The irrigation districts are looking into water conservation solutions, such as piping canals, that will allow more water to be released in the fall and winter months.

“The conservation measures and management practices the districts are implementing will benefit the river and our region’s farmers and communities,” said Horrell. “Our long-term plan is to release more flows during the winter, keeping the side channels connected to the river and eliminating the need for fish rescues.”

During the rescue efforts, volunteers will capture the fish in the pools with nets, hike with the fish to the main channel, identify and count the fish, then return them to the river’s main channel.

The public is encouraged to watch the operation take place. However, electro-shock backpacks are used to temporarily stun the fish, so the sight of stunned fish floating in the pools may be disturbing for some visitors.

The operation will take place near the Lava Island day-use area between 9 a.m. and 4 p.m. For more information on the event, including updates on the date, call the North Unit Irrigation District office at 541-475-3625.

— Reporter: 541-617-7818, mkohn@bendbulletin.com