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Wildlife Protection

Keeping It Simple: Easy Ways to Help Wildlife Along Roads

Rock vortex weirs give tired fish a break

"V" formation is the critical feature of rock vortex weirs used to increase fish habitat. The Idaho Transportation Department built several of these weirs in a swift reach of the Lemhi River along State Highway 28 north of Tendoy. The vortex or "V" of each channel-wide weir points upstream, forcing water and energy towards the center of the weir and creating holding areas below. The deepest holding area is a "plunge pool" - a favorite resting spot for fish on hot summer days. Together, the pools and holding areas help the river's migratory and resident fish, especially Steelhead and Chinook salmon that have come all the way from the ocean some 750 miles away.
--Apr 25, 2003

Tim Cramer, (208) 745-5602 or

Rock vortex weir on Lemhi River
Idaho Transportation Department photo
Rock vortex weir on Lemhi River

On or Along Waterways - Idaho
Updated: 12/12/2012
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