JACKSON (AP) - A bill introduced by the late Sen. Craig Thomas to protect portions of the Snake River headwaters under the Wild and Scenic Rivers Act is drawing opposition from Sen. Larry Craig, R-Idaho.

Craig, who sits on the Senate's Energy and Natural Resources Committee, has said he is concerned the designation of 42 miles of the Snake River between Jackson Lake Dam and Palisades Reservoir would harm water rights held by Idaho farmers.

"That water is used to irrigate farmland in southeast Idaho," Craig spokesman Dan Whiting said Thursday. "His concern is that with the designation it wouldn't be managed for irrigators."

Irrigators in Idaho hold the rights to about 96 percent of the water in Jackson Lake.

Shortly before his death in June, Thomas, R-Wyo., introduced the Snake Headwaters Legacy Act of 2007. It would protect the "outstanding remarkable values" of 397 river miles from things like degradation of water quality and dam building.

Rivers and streams in the bill include Blackrock Creek, Pacific Creek, Granite Creek, Willow Creek, portions of the Buffalo Fork and segments of the Gros Ventre, Hoback, Lewis and Snake rivers.

Protected status does not affect private-property rights and uses or water rights, supporters of the bill stressed.

U.S. Sen. John Barrasso, who was appointed to temporarily replace Thomas, also does not believe the bill affects any existing water rights on the river, his press secretary Cameron Hardy said.

Hardy said Barrasso and Craig have been discussing the issue and Barrasso would be willing to add additional language clarifying the sanctity of those rights.

But Whiting said Craig would not support the bill as long as it includes those 42 miles of the Snake River.

"It is an over-400-mile stretch of river and we are talking about 10 percent, so it seems pretty reasonable, especially if the stretch is between a couple dams," Whiting said. "It doesn't seem particularly wild and scenic."

Tom Patricelli, executive director for the Campaign for the Snake Headwaters, said removing the 42 miles would essentially gut the bill.

"It's hard to have a Snake Headwaters Legacy Act without the Snake River in it," he said.

Patricelli noted that Idaho already has more than 600 miles of rivers and streams that are protected under some form of wild and scenic designation and said the designation "works well" for Idaho businesses and irrigators. Wyoming has 20 river miles protected under the act.

The bill has had one hearing in the Senate energy committee, but the committee has not voted to move it to the Senate floor for a vote.