It is a magic place, this Grand Canyon of the Colorado River. Awesome, forbidding, but strangley soothing.

Through the geologic chaos of red rock fortresses, the river dives a mile into the earth. It dances past waterfalls and tamarisk trees. It surges as frothing rapids, the longest, wildest whitewater in America.

A hundred years ago, John Wesley Powell, a one-armed Civil War veteran and the first white man to explore the river, called it "the most sublime spectacle on earth." Today it is thrapy for victims of future shock.

About 12,000 adventurers -- a tiny fraction of the nearly four million a year who peer over the canyon rim-run the Colorado each summer. Eightly percent of them travel in commercial motorboats.

Now the National Park Service, guardian of the river, wants Congress to designate the canyon an Official wilderness area. As a first step, the service has proposed to phase out motor boats, forcing river-runners to travel by oar -- a longer, quieter journey.

The controversy that has erupted over this proposal in the last six weeks goes to the heart of the nationwide wilderness battle. It pits commerical outfitters and conservative members of Congress angainst environmental groups and the Carter administration.

If the Grand Canyon, one of the seven natural wonders of the work, cannot be protected from noisy traffic jams, environmentalists argue, what can? Park service opponents, on the other hand, see the plan as elitist, restricting one of the nation's premier recreational experiences to those who can afford the time and energy to travel 225 miles by rowboat. The colorado also is a test case in a broader controversy over the growing federal role in regulating the public's use of rivers. The park service and other agencies are developing river management plans and wild and scenic river proposals for dozens of waterways. Officials walk a tightrope between rpeserving the natural qualities of the public domain and encouraging its use.

In the last decade, river-running, like backpacking, has become one of the nation's most popular sports. Traffic on the Colorado River increased 700 percent in the six years before 1973, when the park service began to restrict permits.

But the river has suffered from too much popularity. Twenty-nine park service studies since 1973 document the littering of the river's bank with toilet paper blizzards, human waste and charcoal, the trampling of vegetation and archeological sites and the increasing competiotion for campsites. Conflicts between river-runners increased as flotillas of rubber boats bumped into each other at key attractions along the banks. Those in rowboats complained about the noise and gasoline from motors.

Six years of public hearings and studies produced an inch-thick river management plan. Besides banning motors over the next five years, it would reduce launches from 150 to 50 commercial passengers a day, lengthening the season from April to October to accommodate more passengers. It would increase permits for privatley organized parties from the present 8 percent to 30 percent of the traffic.

"The bottom line," says park service director William J. Whelen, is "a declaration of a value. . . . We want to make it a pure wilderness experience."

Environmentalists boat down the river wearing plastic rain gear, carrying chemical toilets, gas stoves, canned food, cameras and a park service permit.

"This isn't an argument over environment," says Gaylord Staveley, one of 22 commercial outfitters on the river. "It's a technological argument. We're fighting over what technology is going to be used. The park service says by rowing you experience the river on its own terms. I disagree -- the only way to do that is to swim it."

Those opposed to phasing out motorboats contend the action would discriminate against the "fat and flabby," the handicapped and the elderly. The park service, taking pains to disprove this contention, successfully ran a quadraplegic down the river for one study.

Others contend banning motorboats would favor the "idle rich" by lengthening the week-long trip by two days and thus increasing its expense. Trips now cost between $325 and $1000, depending on length -- six to 18 days -- and fringe services. The park service says rowboat trips coat about $75 more than motor runs.

If rowboat trips are limited to the elite, it wasn't apparent in random interviews on a recent run down the river. Joe Longbothan, 29 who delivers packages for United Parcel in Phoenix, was glad to get away from the motors he lives with every day. "Motors disturb the spirit of the place," he said. "The noise blthers me when I'm quietly enjoying a wilderness experience."

Ernest (Buck) Arbuckle 35, had driven from Palo Alto, Calif., to run the river. "There was a section yesterday when there was no sound, the said, pointing upstream. "But it wasn'ta dead silence. The silence was very loud. That was the peace and calm you don't run into anywhere. Then a motor came along with its whine. It robbed me of being out the wilderness."