When river runners swap tales, they tend to focus on fearsome rapids and sneaky currents and rafts flipped like bath toys by a river's force. The channeled exhilaration of riding a tumult of white water has a way of relegating all other river attractions to the background. So it was precisely the absence of such heart-quickening excitement -- the chance to stop and smell the prickly pear -- that led me, along with my brother-in-law Simeon, to sign on for a weeklong trip down the San Juan River in Utah last May.

Though a major tributary of the powerful Colorado River, the San Juan is more forgiving and intimate, renowned for its languorous gooseneck turns and Ancestral Puebloan rock art rather than for boat-gobbling rapids. Thrillingly unexciting, it is the tributary less traveled.

The San Juan River begins its life in the San Juan Mountains of Colorado, flowing southwest into the Navajo Reservoir before continuing generally west into Utah. There, it ultimately meets its premature demise in Lake Powell, the gargantuan dam-formed reservoir that submerged the river's final 70 miles.

Our guided trip, chartered with Wild Rivers Expeditions by the anti-dam Glen Canyon Institute, was to run the lower portion of the surviving river above the reservoir, a leisurely 86-mile stretch that starts outside the tiny town of Bluff, a speck of desert sand in the southeast corner of the Utah map. Simeon, an accomplished landscape painter, hoped to take advantage of the trip's relaxed pace to do oil paintings of the silt-rich San Juan snaking between striated canyon walls.

At the Sand Island put-in, our group of 14 passengers and 5 crew members -- a good-humored bunch predominantly older and female -- loaded our dry bags into four rubber rafts, a wooden dory and a single canoe brought by a pipe-puffing Pennsylvania couple. Before long, our motley flotilla was under way, drifting lazily downriver beneath a cloudless desert sky.

The sensation of escaping modern civilization was immediate. Rowed by our trip leader, Jay Willian, a lanky, bearded vision of head-to-toe khaki, our raft glided quietly over the braided water, flanked by sandstone cliffs, one of them tiger-striped with a dark patina known as desert varnish. A blue heron glided across our bow and perched standoffishly on a tangle of river-scoured driftwood.

The river was placid, so it was only gradually that our senses grew keen enough to notice the crowds -- not of people but of ghosts. For the San Juan is a river of ghosts.

Its side canyons are brimming with the presence of the Ancestral Puebloans, desert farmers who occupied the region for more than 1,300 years, until roughly A.D. 1300. And hovering always downriver, periodically brought to our attention by our guides, was the ghost of Glen Canyon, a sandstone gorge of legendary beauty drowned when the Glen Canyon Dam was completed in 1963 to form Lake Powell.

After pulling into the right riverbank, Jay, a sometime archaeologist, demonstrated how the art and spirits of different eras intermingle along the San Juan. At the Butler Wash panel, pecked into the rock through the blue desert varnish, a row of life-size petroglyph figures greeted us, some with horizontal rays above their heads and flayed human faces below their hands. Thought by some to represent shamans, healers who navigate the spirit world, these figures were created between A.D. 350 and 550 by artists of the Basketmaker II era, who may have sought to incorporate as "spirit helpers" the still-visible smaller figures incised there by their pre-agricultural precursors as far back as 3000 B.C.

A short float downstream, we hiked up a Navajo Nation trail to see a radically different response to the San Juan's ancient spirits. On a wall known as Desecration Panel, petroglyphs had been defaced by a hatchetlike implement, some of the anthropomorphic figures obliterated, others dismembered with strikes to the neck and joints.

"The supposition is that a family was experiencing misfortune or death that indicated witchcraft," Jay said of the defacement, which is thought to have occurred in the mid-1900's. "It was then decided, probably by a healer, that these rock-art figures were related to that witchcraft, and as an attempt to restore balance, the images were defaced."

At Mile 6, our flotilla pulled onto a sand flat, and young and old alike formed a fire line to unload the bags. Our fellow travelers were an engaging lot, many with an abiding personal interest in Western rivers. Sergei was a former Idaho river guide happy to let someone else cook up the fajitas and tall tales for a change. Margie was collecting material -- butterflies as well as metaphors -- for a novel about a lepidopterist-entomologist couple in the Grand Canyon. And Jean, a 73-year-old physicist and kayaker, had actually rafted Glen Canyon before it was inundated.

Soon the after-dark camp talk turned from ancient spirits to personal ghosts, to friends lost in private-plane crashes, and marriages lost in emotional stalls and hard landings of domestic life. A certain fatalism flowed through these conversations, a calmness born, I think, of the San Juan, which never ceased adding its timeless murmur to our voices, the strands of sound braiding into a reassuring chord. This was the river that fed the corn of the Ancestral Puebloans, that mixed with mineral pigments to color their rock paintings. "It's hard to shake the feeling that you're camping in someone else's home," Simeon said.

As it happened, we'd pitched our tents on a floodplain where Ancestral Puebloans likely planted crops, and a short hike the next day brought us to a 14-room dwelling in a sandstone alcove. Called Snake House for the sinuous red-and-white-striped pictograph slithering across the wall above it, the stone and mortar structure was essentially a two-story condominium of the Pueblo III period (A.D. 1100 to 1300). On one wall, painted handprints were adorned with serpentine swirls echoing the river's goosenecks.

Hiking west, we reached San Juan Hill, a harsh incline made famous 600 years after the Ancestral Puebloans abandoned Snake House. In 1879, the Mormon expedition that would ultimately found Bluff -- 250 people and more than a thousand cows and horses -- set out from western Utah. When they neared the San Juan, they hit 700-foot-high Comb Ridge, forcing them to go down to the river and build a wagon trail up the ridge's rocky nose. As I hiked the steep trail with Lori, a vibrant Mormon poet and fellow traveler, she spotted wheel ruts in the sandstone that evoked the struggling teams of the pioneers' horses.

The Mormon expedition's accomplishment in reaching Bluff without losing anyone seemed especially remarkable when our own party began to succumb to the punishing mid-90-degree heat. Nancy was overcome by a migraine while we rowed into the upper canyon our third day, foaming rapids jostling our boats as 800-foot red-and-lime-gray striated walls reared up on either side. And at the last-exit village of Mexican Hat, named for an enormous red-rock sombrero balanced on the canyon rim, she made her escape.

Below Mexican Hat, Lori also fell ill for a day as we floated into the narrow lower canyon and into Mendenhall Loop, a lovely 1.2-mile gooseneck meander around a teardrop-shaped protrusion of land. At camp opposite its downriver side, I heard a sound and spun around, hoping to spot a bighorn sheep. Instead, I saw Simeon, scrambling up to a cliff ledge in his eagerness to paint the peninsula before the sun slipped away.

After a perfect riverside night beneath a star-flecked bowl of sky, Simeon, Sergei and I arose at dawn and paddled inflatable kayaks across the river to the teardrop of land. A trek up a rocky path brought us to the 1890's stone cabin of a gold prospector, Walter Mendenhall, perched on a lofty plateau with the river looping around it on three sides. As we watched, the first sunlight spilled into the canyon, touching the river into flame.

Later, as I retrieved my fleece top from the beach and pulled it on, I leapt back in terror at the sight of a claw-snapping scorpion inside it, inches from my face. I escaped unstung, and Simeon noted that the interloper, with his translucent yellow claws and tail, was as beautiful as he was poisonous.

Day after day, the San Juan bore us through the canyon's sinuous goosenecks, so when the river grew listless around Slickhorn Canyon on Day 6, we had the haunting sense that something unnatural was at work. That something was Glen Canyon Dam, which backs up the Colorado River into Glen Canyon and the lower canyons of the San Juan to form Lake Powell.

After a notorious flood in 1983, the lake extended nearly to Slickhorn, 15 miles upriver of the current boat takeout, laying tons of sediment on the riverbed. To this day, the once robust current is dramatically more feeble here.

A river without gumption, with only a weak whisper of its once resonant voice, is a mournful thing. So I sought out Jean, the septuagenarian naturalist, for clues to what this part of the world had once been like. As we paddled a kayak together the final day, she recalled motoring through Glen Canyon in 1962 on an ungainly vessel made of three Army surplus rubber rafts.

Jean initially had "zero interest" in the region, she told me. But as she set foot in such natural wonders as Music Temple -- a breathtaking grotto named for its marvelous acoustics by the explorer John Wesley Powell in 1869 -- she became heartsick at the canyon's imminent demise.

While Jean spoke, our paddles kept getting caught in sediment, and we ran aground. But despite these frustrating reminders of the reservoir's proximity, Jean avoided becoming mired in nostalgia. "As with any hurt, the pain fades with the years," she said.

Peering from under her straw hat as a turquoise damselfly fluttered by, she urged me to appreciate the beauty of what was left, rather than lamenting what was not.

"For example, I'm happy to see the willows along the shore there by the Russian olives," she exclaimed, sending the ghost of Glen Canyon packing, at least for the afternoon. "Oh, and look at that beautiful desert varnish on the sandstone. You don't see that every day."

A desert paddle

Cortez Municipal Airport in Colorado is about an hour by car from Bluff, Utah. Great Lakes Airlines, (800) 554-5111, www.greatlakesav.com, flies there daily from Denver.

Where to Stay

The Decker House, Post Office Box 69, Bluff, Utah 84512, (435) 672-2304, is a stucco Victorian whose five comfortable rooms with baths begin at $60, with breakfast.

River Trips

A list of outfitters is available from Utah's Canyon Country Visitors Services, (800) 574-4386, www.utahscanyoncountry.com, or on the Bureau of Land Management Web site at www.blm.gov/utah/monticello/riveroutfitters.htm.

Wild Rivers Expeditions, Post Office Box 118, Bluff, Utah 84512, (800) 422-7654, www.riversandruins.com, launches one- to eight-day guided San Juan River journeys from early March through mid-November. The seven-day trip I took to Clay Hills costs $1,095. Meals are included; a tent and sleeping bag costs $15. The three-day trip to Mexican Hat, which includes key archaeological sites, is $525.