Yichang, China ? After a decade of construction and the forced relocation of a half-million people, China closed the sluice gate Sunday at the Three Gorges Dam, a major step toward creating the huge reservoir on the Yangtze River that will power the world’s largest hydroelectric project.

The dam will begin generating electricity for Shanghai and other energy-hungry cities by August, state officials said. But the project is still at least five years from completion, with 600,000 more people due to be moved.

Water flows through diversion holes at the bottom of the Three Gorges Dam. China's Three Gorges Project officially began to store water as the sluice gate of the dam started to be closed as scheduled. China began filling the reservoir behind its gargantuan Three Gorges Dam on Sunday in a major step toward completion of the world-largest hydroelectric project.

The official launch of the reservoir was a subdued affair here at the dam site, with a ceremony put off by the outbreak of severe acute respiratory syndrome and the water slowly starting to fill an upriver basin 350 miles long.

Still, the milestone was roundly lauded by the state media, which sometimes describe the $25 billion project as China’s grandest engineering feat since the Great Wall. But it was widely lamented by critics in and out of China, who said the project would unleash widespread ecological and archaeological harm and forever alter some of the most magnificent scenery on the world’s third-longest river.

Some of those conflicting sentiments were on display Saturday night in the relocated village of Maoping, where tens of thousands of residents who used to live along the river gazed down upon it and the gigantic dam from high-rise buildings set up in the hills. Many considered themselves lucky to at least be nearby: Some peasants have been moved by the government to factory jobs in faraway cities or to construction projects in the remote Xinjiang region of China’s northwest.

“It makes me very proud for China,” said Lu Yenshang, 34, an agricultural official who was gazing at the project with his 9-year-old son, Yingqi, as the surrounding mountains turned purple in the hazy sunset and floodlights came up on the dam. “When you build the biggest dam on Earth, people know you have a great nation.”