The Idaho Water Users Association says the bill, which passed the Senate Energy and Natural Resources Committee on Wednesday, could impinge on Idaho's historic water deals.

The bill now goes to the full Senate.

The bill calls for the "wild and scenic" designation for 387 miles on 13 rivers.

The Idaho water users are against designating 42 miles of river that is atop the Minidoka Project.

Norm Semanko, executive director of the Idaho association, said in a news release that he fears what will happen if "federal bureaucrats" decide to pressure the Bureau of Reclamation to change water policies that might harm Idaho irrigators.

"We are dead-set against any federal protection designation for that 42-mile stretch of the Snake River below Jackson dam," he said.

Tom Patricelli, a spokesman for the Campaign for the Snake Headwaters, said Idaho irrigators have nothing to fear from the wild and scenic designation.

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

Wyoming Sen. John Barrasso inserted "unprecedented" water language that declares the "sanctity and superiority" of all water rights in Wyoming and Idaho, Patricelli said.

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

Idaho Sen. Larry Craig, a Republican, offered two amendments to the bill to ensure that Idaho water rights are protectd after the designation. They were both defeated.

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

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

There are currently more than 11,000 miles of wild and scenic rivers in the country.

Wyoming ranks near the bottom of the list, with only 20 wild and scenic river miles. Idaho has 574 miles, mainly in the Frank Church-River of No Return Wilderness.

Wild and scenic designations protect water quality and the free-flowing nature of a river while allowing continued multiple use, such as fishing, hunting, camping, boating, snowmobile riding, ATV use and livestock grazing.