We are sitting in an old school bus, with the windows closed, 300 yards from a river we cannot see and should not be able to hear. But it sounds like Niagara Falls. It sounds like a river we should not ride in rubber rafts. And the last-minute instructions from our river guide do nothing to dispel that notion.

"Be sure and make friends with someone in your raft so they can grab you if you fall out," said Bud Frantz in a voice that attempted cheer. "You'll enjoy this trip a lot more if you stay inside the boat."

Welcome to the Gauley River, the most ferocious, fast-moving, beautifully challenging whitewater river in the East. This river in southern West Virginia, about 6 1/2 hours by car from Washington, is so tumultuous that guides who have made the trip a hundred times still say their prayers before every run.

"You make a mistake on that river and you're gonna pay for it," said Audie Critchley, a guide for Class VI Expeditions, one of a dozen outfitters that provide rafting trips down the Gauley in the spring and fall. Critchley grew up in the area. He wears a felt hat decorated with a snakeskin band and speaks with an accent that immediately reminds you of the movie "Deliverance." When he talks, we listen.

Here is what Paul Davidson and Bob Burrell have to say about the Gauley in their book, "Wild Water West Virginia."

"Pull out all stops on the superlatives to describe this unique wild water river. It is the absolute swirling, pounding, crashing end . . . The Gauley has become the East's qualifying cruise for the title of expert paddler. It is big, it is long, it is inaccessible, it is tough, it is dangerous, it is intoxicating."

The whitewater section of the Gauley begins just below an enormous dam at Summersville. In the next 26 miles there are 100 rapids. Half are rated difficult to extremely dangerous during the spring and fall when the Army Corps of Engineers releases water from the dam.

But last year the corps released a proposal for the river that was as turbulent as any of its rapids. The corps wants to build a hydroelectric generating station three miles below the Summersville Dam. If approved, the project would reroute all but a stream of water from the upper portion of the river through an artificial tunnel. The prospect has upset whitewater enthusiasts, fishermen, boaters and conservationists.

The corps says its $120 million project would generate 4 million kilowatt hours of electricity per year to help America lessen its dependency on foreign oil. Corps officials argue that the river would still contain more than 21 miles of good rapids and, because electricity would be generated year round, it would provide more days each year for rafting and kayaking. The corps has also appealed to anglers by promising to stock the upper river with trout.

Opponents of the plan dispute every point. They say whitewater boating on the lower portion of the river may be impractical because water from the powerhouse will not reach that section until too late in the day. Because peak generating periods occur during the week, there are no guarantees that the corps will make any releases of water on weekends when most people use the river. Another part of the corps plan, to raise the existing lake by 16 feet, would damage fishing and flood coal reserves for the sake of electricity that may not be needed, they contend.

"Our country is so shortsighted. There aren't many of these rivers left," said Chris Brown, the director of the American Rivers Conservation Council, a Washington based nonprofit group dedicated to protecting this country's wild rivers.

There is much irony in this dispute. Before the corps completed the Summersville Dam in 1966, there was no rafting on the Gauley. A handful of daring kayakers had run the river during spring thaws. But the volume of water was so unpredictable, no commercial rafting company dared take customers on a run.

"Without the dam, you wouldn't have any whitewater," said Bill Brown, an official with the corps at its Huntington, W.Va., office.

"We are in a difficult situation," conceded Edward B. Rhett, a 34-year-old computer programmer from Charleston and vice president of Citizens For Gauley River, which claims a membership of 300. "We are the same people who year after year have to ask the corps for their cooperation. Now we are the same ones opposing them. It's like biting the hand that feeds you."

The fight over this hydroelectric project has generated more than a little interest because of the river's raw power, unspoiled beauty and economic impact on the surrounding area. The money spent by rafters and other recreational users of the lake and river (772,000 in 1981) has made local motel and restaurant owners who have never put a foot in the river staunch supporters of keeping it the way it is.

The West Virginia legislature, the governor, conservation groups and the National Park Service are all involved in the dispute. Meanwhile, people continue to pay money to ride rubber rafts through rapids with names like Gateway to Heaven, Pure Screaming Hell and Mash.

"This is the most fun I've ever had in West Virginia," said one soaking-wet woman after surviving the trip. "And I've lived here all my life."