When President Carter signed the bill authorizing completion to the Tellico Dam last week, a collective cringe spread among conservationists and anglers across the country.

In the talk of the snail darter, the economics of the dam project and the seedy business of vote-trading in Congress, the fact that the Little T is widely regarded as the best trout stream in the East got lost.

Fishermen/conservationists had breathed a sigh of relief last January after the newly created Endangered Species Committee voted unanimously not to exempt Tellico from the requirements of the act. After a decade of legal battling, it looked as if the Little Tennessee and the rich archaeological and historical bottomlands around it would be saved for good. The committee said the project not only was environmentally unsound and economically ill-conceived, but also violated safety regulations and the Historic Preservation Act, among other laws.

Conservationists will likely issue further challenges to the bill's passage into law, but with the language of the bill this emphatic, there's little room for hope for the Little T.

Which means you'd better go now if you'd like to fish one of the country's legendary trout rivers before it's inundated. Just south of Knoxville, the Little T is about an eight- or nine-hour drive from Washington -- in easy range for a three- or four-day weekend.

Fall is a lovely time to fish the river, even with the sad knowledge that this is probably a premature autumn for the river's life as well. Fishing pressure is slight during this season, nights are crisp and frosty, and the Great Smoky Mountains looming up behind the river will be taking on rich hues of gold.

The Little T was born as trout water in 1944, when the new Fontana Dam gathered the clear, cold waters of hundreds of miles of Smoky Mountain and Nantahala National Forest trout streams. From Fontana, the water staircases through three more dams before being released from Chilhowee Lake at 45 to 50 degrees. Throughout its remaining 33 free-flowing miles (the first 17 inhabited by trout), the water temperature does not rise above 62 degrees.

An average width of 125 yards makes the Little T comparable to the broadest western rivers such as the Madison and lower Yellowstone. It's also one of the most fertile trout rivers anywhere: Samplings show up to 100 mayfly nymphs and 200 caddis larvae per square foot of river bottom.

"The feeder creeks that drain from the Smokies are acidic and not very fertile," says Price Wilkins, head of Tennessee's coldwater fisheries program, "but the bed of the Little T is composed of limestone and dolomite. This provides a helpful buffering effect and gives the river a pH reading approaching neutral, which is favorable for food production."

Browns and rainbows reproduce some in the river, but not enough to take full advantage of the stream's rich food supplies. Ten thousand adult fish and 100,000 rainbow fingerlings are stocked annually, but Wilkins feels that the river could support plantings of a million fingerlings a year without a strain, so rich is its invertebrate life.

Survival rate of fingerlings in the river is eight times that found in the state's best mountain streams, and growth of young trout in the Little T equals the best obtained in hatcheries. "A rainbow of 18 to 22 inches is a good fish here, but 12- to 16-inchers are common," says Wilkins. Browns may range up to 20 pounds.

A float trip is the best way to appreciate this huge river, but there are many shallow shoals up to 200 yards wide where it's fun to get out and wade. Short drifts can be taken from the public launching ramp on Tennessee Route 72, just east of Tallahassee, down four or five miles to one of a number of pull-offs along the road.

A better plan still is to float the entire 15 miles of trout water from the boat ramp down to the U.S. 411 bridge at McGhee. Take along a sleeping bag and camp on the TVA land along the river. The takeout point is on the south side of 411, on a small abandoned road at the mouth of a feeder creek. Either johnboats or canoes work fine.

Water releases from Chilhowee Dam are something to watch out for, as on any tailwater fishery. The most enjoyable angling comes at minimum flow (1,350 cubic feet per second), or slightly above this release rate. The river flows at an average depth of three feet, and the boat drifts gently downstream under these conditions. Trout rise well to flies and spin fishermen using ultra-light tackle and Mepps, Shysters and Panther Martins also take fish.

If the water is high and fast, heavier lures are required and boats will be whisked downstream. Wading is dangerous at these times. The one good thing is that heavy water releases stimulate trophy browns to feed. Casting Spoonbill Rebels, Countdown Rapalas and heavy spinners can yield fish as long as your arm holds out.

A weekend forecast of water releases is available by phoning 800/251-9242, a toll-free number for those living in Virginia. Maryland and D.C. residents can phone 615/251-9242 at standard rates to receive the same information.

To fish the Little Tennessee you need a trout stamp ($5.30) and fishing license ($3.30 for three-day; $5.30 for 10-day). They're available at sporting goods and country stores near the river.

The trout fishing typically ranges from good to outstanding, but this is one place where the beauty of the surroundings often takes the forefront, even for fanatics. On a recent fall float trip here we saw half a dozen boats on the first five miles of river, near the road, then not a single other angler for the next 10 miles, until we reached the take-out at McGhee. An osprey drifted through azure skies and doves flushed with whistling wings from yellowing trees along the bank. Marsh hawks jockeyed from tree to tree to elude pestering crows, and killdeer flitted across the silken currents.

The valleyland along the river is the former homeland of the Cherokee nation, and over a thousand artifacts have been dug up at some 285 separate archaeological sites that are soon to be flooded. We floated past Chota, the capital of the Cherokee nation, and cast our spinners and flies along the banks of Tenase, the "city of refuge," where Tennessee got its name.

But hurry if you want to see this lovely river, or catch it plentiful trout. Barring a miracle, all will soon be flooded, and a listless Tellico Lake will take its place along with the other 20 impoundments within a hundred-mile radius of the river.