Yangtze Dam Nears Completion

Construction of the world's largest hydroelectric project, a dam spanning China's Yangtze River, nears completion

The Three Gorges dam is intended to provide flood control and, when all the generators are operational in 2009, massive amounts of hydroelectric power.

The bottom images shows construction underway on the partially completed dam in July 2000, when sediment-filled water still flows freely through a narrow channel near the river's south bank (bottom left). A smaller passage closer to the north bank of the river, where water appears calmer, is a system of temporary locks that allow for boat passage. A second system of locks appears to be under construction about half a mile to the north.

By May 15, 2006 (top image), workers were pouring the last of the concrete to finish the project, according to Chinese news media. The dam currently spans the entire river, and a large reservoir--which is more than 2 miles across further upstream--has filled in behind it. White spray shoots through gates at the center of the dam, and the former locks are much less prominent, giving way to the new ones near the north, which appear as thin, blue rectangles.

--Bjorn Carey

Amazing Images: Science & Nature Photos from Our Readers

Credit: Jesse Allen, NASA Earth Observatory, NASA/GSFC/MITI/ERSDAC/JAROS