Summer 1980: Steve Harris and Janet Long arrive in West Virginia about as nervous as they are excited. They manage to negotiate the beautiful Lost River in a brand-new 16- foot canoe with a minimum of capsizes. They are enthralled. Summer 1981: The Shenandoah is up. There is a picnic on a rock. Out in the fast, big current two boats come sweeping by, a high-performance open canoe and a sleek kayak, each being paddled skillfully. It's Harris and Long, one year later. The allure of rivers creates whitewater addicts. A well-planned trip offers physical challenge, unexpected beauty, good company, good food, a genuinely leisurely pace punctuated by moments of high sport, even a little fear. It's easy to get hooked the way Harris and Long have. In a year, paddling has become their sport. They've either tried or know about all the good stretches of the area rivers -- the Cacapon, the Potomac, Shenandoah, Rappahannock and the little feeder creeks that swell and rumble after a good rain. In the fall the challenge declines on these streams but the beauty escalates. So last week Harris and Long organized a five-boat assault on The Needles, a moderately gentle, scenic stretch of the Potomac that starts just above Harpers Ferry and ends below the Potomac's confluence with the Shenandoah. It was not truly autumn, but the signs of fall were everywhere. There was a cool, following breeze instead of the close stillness of August. The river was all but empty, summer crowds having abandoned the banks in favor of football games on television and work around the house. There was the faintest tinge of dry gold in the sycamore leaves, which rattled in the breeze. "There is a nice eagle," said Manuel Mu?noz, pointing at the skyline downriver where a bald eagle flapped away, its white underside brilliant alongside the black of its wings. The Needles is a short run. You could complete it in 90 minutes by hurrying. It offers a couple of perfect lunch spots. The group stopped at the first one, a stand of black boulders perched on a ledge over which the river cascaded. There was a protected swimming hole at their feet. Lunch: Roast leg of wild boar; home-made bread; a bulgur wheat salad; sliced tomatoes from the garden; fruit salad, strawberries, beer, wine, cookies. A fisherman waded the pool just downstream. First he cast lures without success. He switched to bait, set out two rods and within minutes was catching bass, bluegills and catfish so fast he often had both rods occupied and not enough hands to crank the fish in, which makes for a delightful dilemma. He threw back every fish he caught. After lunch they swam a bit. When they normally would have put in and restarted the descent down the river, they climbed back on the rocks and sat around awhile longer, lingering, soaking up the autumn sun. The trip seemed too short. The sunlight would give out at 7:30 or so. At 5 they were half a mile from the takeout. Pat Mu?noz pulled her kayak into a cove behind another rock. She waved the others over. They had lunch again.

GETTING ON THE RIVER

Washington's resident expert on canoeing and rivers is Pat Mu?noz (the same one who demanded a second lunch). She organizes river exploration trips for the American Rivers Conservation Council. She shares the view that fall is the loveliest time on the river. Here, based on her experience, are some recommendations on area outfitters who can provide rental boats, guided trips and advice to prospective paddlers on appropriate autumn voyages.

POTOMAC RIVER

RIVER AND TRAIL OUTFITTERS, Knoxville, Maryland, specializes in the area around Harpers Ferry. Knoxville is about an hour's drive from Washington. Phone 301/834-9952. POTOMAC RIVER TOURS specializes in raft trips down the Mather Gorge, 10 miles from downtown Washington. Phone 530-8733.

SHENANDOAH RIVER

SHENANDOAH RIVER OUTFITTERS specializes in the upper stretches of the river near Luray. It's about a two-hour drive from Washington. Phone 703/743- 4159.

DOWNRIVER CANOE CO. near Front Royal is a half- hour closer to Washington and handles trips farther downstream. Phone 703/635-5526.

RAPPAHANNOCK RIVER

KELLY'S FORD OUTFITTERS offers trips on the popular section near Remington, a 90-minute drive from town. Phone 703/439-8740.

SPRINGRIVER CORP. in Falls Church and Rockville rents canoes, kayaks and rafts and offers advice. Phone 881-5696.

Mu?noz also has several fall ARCC trips open to the public, including voyages to the New and Gauley Rivers and the New Jersey Pine Barrens next month. Call 547-6900. And for folks willing to drive, she recommends a fall trip down the Youghiougheny River at Confluence, Pennsylvania, a four- hour drive from Washington. The Middle Yough is wild, but not too wild for novices, and sits between two big-water stretches of the river that are considered high sport for experts. RIVER PASS OUTFITTERS runs Middle Yough trips. Phone 814/395-3136.