OUT IN IDAHO, Sen. Frank Church reports, the Salmon River basin and the land adjoining it are known as "God's country." Quite so. The area, rich in mountains, streams and wildlife, is among the nation's most beautiful and unspoiled places. The House of Representatives has a chance to keep it that way this week when it takes up the River of No Return Wilderness bill.

The Senate voted last November to set aside 2.2 million acres of federally owned land -- almost 5 percent of the state of Idaho -- in this new wilderness area. The tract would be the largest in the continental United States to be placed in this category of federal property where controls on development and exploitation are most stringent.

Unfortunately, the bill has emerged from the House Interior Committee with 50,000 acres carved out. This land, winter home of a large herd of bighorn sheep, may contain cobalt, and a majority of the committee apparently believed access to that important resource would be too severely impaired if it were included in a wilderness area. But this is not a justified anxiety: the Senate bill made provision for mining of the cobalt -- if it exists -- in ways that would permit some of the wild values of the area to be maintained. The Senate provision strikes a careful balance between exploitation and preservation. The House should overrule its committee's exclusion of the West Panther Creek/Clear Creek areas from the bill.

It seems likely that an attempt will be made on the House floor to use this bill as a vehicle for opening up all the other roadless areas in Idaho. The idea sounds plausible: with this much wilderness, why not ease the restrictions on how the rest of the federal land in the state is used? The answer is that the proper disposition of each large tract of federal land, in Idaho or elsewhere, should be decided independently after careful consideration of whether it should be used as wilderness or national forest or something else.

The version of the River of No Return Wilderness bill that Sen. Church skillfully guided through the Senate produced an unusual accord among loggers and backpackers and even some miners. They recognized that the real value of this large area of Idaho is its unspoiled condition and that it is unspoiled because it has been inaccessible until recent times. By voting to designate it as a wilderness, the House can help keep it that way.