IDAHO FALLS, Idaho — The Idaho Water Users Association has come out against a federal bill to designate 387 miles of the Snake River as wild and scenic, out of concern that historic water rights could be impinged in eastern Idaho.

"We are dead-set against any federal protection designation for that 42-mile stretch of the Snake River below Jackson Dam," Norm Semanko, executive director of the association, told the Post Register.

That portion of the Snake River flows mostly in western Wyoming before reaching Palisades Reservoir in eastern Idaho.

The Senate Energy and Natural Resources Committee on Wednesday approved a bill to designate 387 miles of the Snake River as wild and scenic. That designation affords protection of parts of the river and its immediate environment. The bill now goes to the full Senate.

Sen. Larry Craig, R-Idaho, offered two amendments to ensure that Idaho water rights were protected after the designation. They were both defeated.

Craig said he is concerned the flow of the river would be affected once it gets to Idaho.

The river "starts in Wyoming, but its water belongs to Idaho and is Idaho's most significant water source," Craig said.

Sen. John Barrasso, R-Wyo., introduced the bill.

A spokesman for the Campaign for the Snake Headwaters, Tom Patricelli, said Idaho irrigators would not be affected by the designation.

"This bill unequivocally declares that all water rights in Wyoming and Idaho are unaffected," he said.

He added that Barrasso inserted "unprecedented" water language that declares the "sanctity and superiority" of all water rights in Wyoming and Idaho.

"Nothing shall affect the management and operation of Jackson Lake or Jackson Lake Dam," he said.

Semanko said he fears that "federal bureaucrats" will pressure agencies to change water policies that could harm irrigators in Idaho.

The U.S. has more than 11,000 miles of wild and scenic rivers, but Wyoming is at the bottom of the list with only 20 wild and scenic river miles. Idaho has 574.

Designating a river as wild and scenic protects water quality and the free-flowing nature of a river while allowing activities such as fishing, hunting, camping, boating, snowmobile riding, ATV use and livestock grazing.