T o a person more comfortable in the last century than this one, Up the Yangtze gives the sense of what the next decades will be like. It all looks about as welcoming as an open grave. Director Yung Chang, a master documentary filmmaker from Canada, starts with immense iron walls closing in on the camera. They are the vast locks on the Yangtze River.

The chamber fills with water. In claustrophobic close-up, we are pressed against the narrow clearance between a wall and a ship. We rise with the boat to get the lay of the land. The images open to the wide top of a dam and a snarl of electrical transformers.

Up the Yangtze 's subject is the Three Gorges Dam project. I'm relying on stats from TreeHugger.com, which claim that Three Gorges is five times as wide as the Hoover Dam and is inundating 244 square miles of territory, causing the eviction of a million people. We have all heard that the Great Wall of China is an object big enough to be seen from the moon. It isn't; this dam is.

This plan has been desired ever since Mao Zedong was alive. The soundtrack has an opera singer groaning out a musical version of Mao's poem on the subject: "The mountain goddess, if she is still there, will marvel at a world so changed." And the change has no end in sight in Up the Yangtze 's view. The film takes this massive undertaking and boils it down to a simple matter of scarce arable land being submerged and pleasure craft for the rich cruising over it.

Yung contrasts two different young people to illustrate the change. The Yu family, who come from the so-called ghost city of Fengdu, has been relocated to a handmade shanty. They add to their scarce money by farming corn and rice on the ever-receding margin of the river. Father Yu is a scrawny, hard-muscled worker of the kind who has been exploited ever since the emperors.

The eldest daughter, Yu Shui, wants to go to school, but there's no money for that. To support her family, she must take a job as a "barbarian handler," if that's still the slang—specifically, a job as a hostess aboard a riverboat for tourists. Yung had remarkable access to the crew of the Victoria Princess on a "farewell tour" of the Yangtze. Renamed "Cindy" for the trip, Shui is brought up to speed the hard way, taught forced smiles and etiquette.

Chen Bo Yu, no relation, gets the friendly-for-Westerners nickname "Jerry." He's the slicker, more self-assured single son of an affluent family. The Yu family's life is candle-powered, but Chen's world is neon. The camera circles around him as he walks downtown in a riot of signs and electric advertisements, as if he is dizzied by the vortex of light. After an evening of karaoke and shots of European vodka, this 19-year-old gets the cushier job of bartending on the boat.

Yung's specialty is the no-comment compare-and-contrast, with careful attention paid to the passing of time. We can see it pass by watching the Yus' squatter cabin become an island on the water. The director needs no additional commentary when traveling on the river road. In one flooded town, a small-time antique dealer collapses into shockingly sudden tears over political corruption: "Some officials are like bandits, beating, robbing."

Up the Yangtze doesn't stick it to the tourists, so infantilized by luxury that they are bussed out to see a model home for the relocated in a strategy that wouldn't fool a time-share sales sucker. But what can they do except smile politely when their guide warbles, "Seeing is believing! Would you like to look with your own eyes?" A tour guide named Campbell has a joke about the direction of things in China: the trick is to make a show of communism while going capitalist. Then Campbell quotes Mao on the idea that the color of a cat doesn't matter as long as it catches rats.

Are the rats being caught? The sights we see suggest not. Yung got a lot of news out of this secretive nation, showing us a violent protest of displaced citizens who haven't been given houses yet. The ever-increasing class struggle is masked with paeans to new opportunities. The downside of such remorseless central planning only gets exposed after catastrophes, such as the recent quake.

While watching the ancient, legendary China drown by inches, Yung sticks with the human costs. The Yus end up stashed in a concrete bunker that looks like an air-raid shelter. We last see the river's titanic iron lock at night, glowing in iodine-colored light. Oliver Goldsmith's poem—"Ill fares the land"—runs through one's mind, seeing all this suffering. We have no clear idea what happens next.

'Up the Yangtze' opens on Friday, June 13, at the Smith Rafael Film Center, 1118 Fourth St., San Rafael. 415.454.1222.

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