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Cold-water bypass gains steam

News editor | April 8, 2018 1:00 AM

PRIEST RIVER — A proposal to direct water from the chillier deeps of Priest Lake to aid native fish populations in the Priest River is gaining momentum.

Idaho Department of Fish & Game officials advised the Idaho Lakes Commission meeting on Friday that $70,000 has been obtained to pay for an alternatives assessment for the project.

Originally referred to as a siphon concept, Fish & Game has rechristened it a cold-water bypass concept to avoid the baggage the term “siphon” can carry with it, particularly the impression that something is being taken, according to Kiira Siitari, an environmental staff biologist with Fish & Game.

Siitari told lakes commissioners the assessment funding was secured through the Clark Fork Settlement Agreement involving federal hydroelectric projects in the basin.

“The alternatives assessment is really the first step,” Siitari said.

Sketched broadly, the concept involves running a pipe from the hypolimnion — the dense bottom layer of the thermally stratified lake — and directing the water to the river to improve habitat conditions for native species such as bull trout. The concept caught the attention of Fish & Game and the commission after a similar project on Washington state’s Sullivan Lake showed success in cooling downstream temperatures.

Modeling performed by Portland State University indicated that a conservative amount of water drawn from the hypolimnetic portion of the lake can bring the river temperatures to about 66 degrees, a sweet spot for cold-water trout species.

“Even small changes here are going to make a difference,” Siitari told commissioners.

In addition to aiding bull trout, conditions for other trout species will also improve, which could be used to market the river as a high-quality angling destination on par with the Coeur d’Alene and St. Joe rivers. The Coeur d’Alene River generates $3.1 million in annual tourism revenue, while the St. Joe generates $4.1 million, according to Fish & Game estimates.

The bypass concept is not expected to diminish the level of Priest Lake or affect its hypolimnion. As little as 4 percent of that layer of water could be directed into the river.

However, Fish & Game isn’t taking any chances and said a hard look will be taken at potential impacts.

“It’s a pretty small slice, but it’s not something we want to overlook,” Siitari said.

Keith Kinnaird can be reached by email at and follow him on Twitter @KeithDailyBee.

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