It's a long way to the source of the Mekong: a three-day journey by four-wheel drive from the nearest airport in the city of Xining, about 825 miles southwest of Beijing, and then another day on horseback.

But early on, I met some travelers whose journey made mine seem easy.

Step, Step, Slide

Two young Buddhist monks on a pilgrimage to the Tibetan city of Lhasa — the first of several groups I'll come across on this road — will walk and slide on their chests, protected by leather aprons, all the way. Their hands are strapped to wooden blocks covered in a thin sheet of metal, as they fling themselves to the pavement — and closer to their goal.

It's more than 400 miles from their monastery to Lhasa. Their journey, one of the monks says, will take six months.

It will be hard, he says, but worth it: a chance to pray at the Jokhang Temple in Lhasa — considered by most Tibetans to be the most sacred and important temple — and accumulate merit and good karma along the way.

This makes perfect sense to my Tibetan colleagues, who are also looking for good karma, or at least a little help, on our journey. And they regularly ask for it — shout for it, actually — at the high mountain passes on our way.

The passes are draped in brightly colored prayer flags left by previous travelers. The shouting, the guide explains, is an offering both to God and to the local mountain deities to protect us on our journey.

A little luck doesn't hurt on this highway, where landslides or avalanches can cut the road for days, even weeks.

Birthplace Of Great Rivers

The Tibetan plateau is the source of almost all of Asia's great rivers — the Yangtze, the Ganges and the Mekong among them. It's the largest source of freshwater outside the polar ice caps.

The Chinese occupied the area some 60 years ago, but they stick mainly to the towns. The countryside is still the domain of Tibetan nomads.

Three days into our journey, we go off-road and upriver, traveling along the rocky bed of the Mekong. Here, it's a glacial stream — clear, icy cold and sweet.

Our destination for the evening is a small, mud-walled shack on a bluff overlooking the river. Outside the house, three Tibetan mastiffs bark, demanding to know why we're here.

Our host, Sonam Yarpel, spends the harsh Tibetan winters here with his yaks and his family. He says he gets to the nearest town maybe twice a year, to sell yak butter and cheese. The family burns dried yak dung for heat, but has a solar-powered television and DVD player.

Politics And Song

The solar panel is a gift from the Chinese government, he says. The government would probably be less than happy to know he has a picture of Tibet's exiled spiritual leader, the Dalai Lama, hanging on the wall.

The next morning, our host lends us a few horses for the final push to the source of the Mekong. Sure-footed and even tempered, the horses pick their way carefully through the icy river and boggy terrain. The previous day, we spotted a pack of wolves loping alongside the river. On this day, we spy mountain gazelles, eagles and wild donkeys.

My guide — a Tibetan country boy who now lives in the city and doesn't get out nearly enough — surprises me when he starts singing as we ride.

To be honest, this kind of behavior is usually embarrassing to me. But not this time.

And when I ask him why he's singing, he just laughs, as if I'm the idiot. Of course, he's right. He's Tibetan; he's on a horse, in the mountains, far from anyone or anything that could bother him. Why wouldn't he be singing?

His mood changes, though, when we talk about the Chinese government's efforts to rein in the nomads, to fence in their traditional grazing areas, and resettle them in towns. The government says it's an effort to avoid environmental degradation. The Tibetans in this region see it as another attempt by China to wipe out their traditions and their culture.

The weather turns abruptly. The sun disappears. Snow begins to fall, and I start to worry.

A Tiny Trickle

But by early afternoon, in a near whiteout, we finally reach our destination: a tiny marker and an even tinier trickle coming from rock more than 3 miles above sea level, some 3,000 miles from where the Mekong finally empties into the South China Sea.

My guide declares that we are at the "real" source of the Mekong, which is known in Chinese as the Lancang Jiang and in Tibetan as the Dzachu.

"This is the original source. We can see the tiny stream coming under the rock, and this is the real source of the Mekong River, I think," he says.

But the source of the Mekong, like many other things in Tibet, is under dispute. We are at the location that the Chinese government says is the river's source, while some Tibetans believe the river originates elsewhere.

Either way, my guide agrees, both trickles meet and form the river known as the Dzachu, which has spiritual significance for Tibetans, who have a reputation for being close to nature.

Water Spirits

My guide says his people believe in spirits of water known as nagas.

"When we are kids, we are told by our parents, if you do anything to the spring or to the river, nagas will pay you back, like make you sick or [give you] bad fortune or bad luck," he says.

Some Tibetans say that bad luck has come already to the river, to the town named for it, Dzato, which lies some 40 miles to the southeast of the source.

A decade ago, Dzato was a frontier outpost of single-story buildings. Today, it is a boomtown — apartment blocks and businesses sprouting like weeds in the shadow of the mountains and the stupa, or holy Buddhist structure containing relics, on the hill.

On the southern bank of the mocha-colored river, construction of a new entertainment complex — complete with cinema and Internet cafe — is under way. Raw sewage flows into the water directly across from us, near a small mountain of trash.

All of this is too much for one longtime resident, who doesn't want to give his name.

"All the sewage from the town — from the hospital, from the restaurants, from the houses — everything gets thrown into the river. And it's not just the Chinese doing it, it's young Tibetans, too. All they care about is making money," he says.

Taming The River

A few miles downriver, a small hydropower station has been built to provide electricity for Dzato and the surrounding area. The Chinese have already built several dams on the river they call Lancang Jiang, which means "turbulent river" — with more dams planned. The largest is at Manwan, several hundred miles downriver in China's southwest Yunnan province, where the river has been tamed.

Above the massive Manwan Dam, the Mekong is now a large, deep reservoir that stretches for miles, and the power it generates has helped fuel China's economic boom and the jobs that have come with it.

While environmentalists worry about the dam's effects on local communities and on fisheries downstream, boatman Zhi Huazhou is having none of it.

"I make a lot more money giving boat rides to tourists than I did as a farmer," he says.

"Sure, some villages were destroyed when this place was flooded, but the people were compensated. Some complain it wasn't enough, but everyone has a different perspective, I guess. But for me, the dam has been a good thing," Zhi says.

Others who live along the river in Yunnan province aren't convinced.

Local Cultures Under Threat

Mai Yan, 35, runs a small hotel not far from where the Mekong tumbles out of the Tibetan plateau in a torrent, in an area that is home to many ethnic minorities. The government is planning several more dams that may leave her town and several others in the valley underwater, she says.

Like many here, she is uneasy with the prospect and troubled by the influx of majority Han Chinese that development has brought to the area. Her father is from the ethnic Hui minority; she is a mix of Hui and Bai; and her husband is from yet another ethnic minority, the Lisu.

"Before, this village was mostly Bai, and that was the language spoken here. But now, the majority is Han, and the main language is Chinese," she says. "The older generation still speaks their own language, but for younger people like me, our first language is Chinese."

A geologist working for a local mining company listens intently from a nearby table, then pulls me aside as we're leaving. He's ethnic Bai, too, and views the Han Chinese with suspicion. There are a lot more Han than the government says there are, he says, and more and more are moving here.

The Chinese, he says softly, are dangerous.

To whom? I ask.

To the ethnic minorities, and to our neighbors, he says.

Downriver To Myanmar

On the dock in Guanlei, a Mekong River port in Yunnan across the river from the Myanmar border, workers load fresh fruit — mainly apples — onto Chinese riverboats bound for the markets of Bangkok and beyond.

The trip down the Mekong to northern Thailand will take 10 hours or so — longer, a crew member says, if the boats have to wait for the dam upriver to release enough water to allow their heavily laden vessels to pass.

Our captain eases his 100-foot-long boat downriver, where it quickly gathers speed in the swift current. The ship seems too big to navigate its way through the narrow and rock-strewn rapids, where the river isn't much wider than our vessel.

But the captain knows what he's doing. And where the river widens, other boats pass us heading north, stacked high with timber and cars, feeding China's growing appetite for both.

At sunset, the boat heads downriver from Guanlei, China, to Thailand.

There's a light rain falling and a magnificent rainbow, which I take as an auspicious sign. To the boat's right is Myanmar, the hills carpeted in forest. To the left — for a while at least — it's still China.

More than 1,000 miles from its source, the Mekong is almost three times lower here in southern China than it was when it started, as a tiny trickle high in the mountains.

But even in southern China, the river is still more than half a mile above sea level.

Producer Tung Ngo contributed to this report.

Still ahead: Myanmar, Laos, Thailand, Cambodia and Vietnam.