The World's Tallest Sand-and-Gravel Dam Starts Generating Power in the Tianshan
China's newest 'superproject': the 247-meter Dashixia dam, the world's tallest of its type, has begun generating power in a Tianshan gorge — electricity for some 600,000 households and 3.4 billion cubic meters of annual water for the Tarim River.
Deep in a gorge of the Tianshan range, where the Kumalak River drops out of the mountains toward the Aksu plain, the first two generating units of the Dashixia water conservancy project went onto the grid on September 29. State media carried the moment under a hashtag promising "another superproject deep in the Tianshan" (天山深处再现超级工程) — and the superlative is more than branding: at 247 meters, Dashixia's concrete-face sand-gravel dam is the tallest structure of its kind in the world.
Sand and gravel instead of poured concrete is a deliberate choice for a dam standing in one of China's more earthquake-prone corners: the material is locally sourced and can flex through shaking that would crack a rigid wall. CCTV Finance reported that builders leaned on "smart construction" systems to clear a set of world-class difficulties — high seismic intensity, high slopes, and high spillway flow speeds — before the first units could run. The turbines themselves are a first for China: Francis-type units fitted with cylindrical valves adapted to high water heads and heavy sediment, a necessity on a river that carries the Tianshan's grit down to the plain.
The completed station will hold three 250-megawatt turbines — 750 megawatts in all — generating about 1.89 billion kilowatt-hours a year, enough, by Xinhua's arithmetic, for roughly 600,000 households, with a dispatch role shaving peak load across southern Xinjiang's four prefectures. The water side of the ledger matters more locally: the reservoir will release 3.42 billion cubic meters a year toward the Tarim River, irrigate about 450,000 hectares of Aksu farmland, and lift downstream flood protection from a once-a-decade standard to once in fifty years.
On Zhihu, where a trending question asks why anyone builds a giant reservoir in arid gobi country, an account from the project supplies the texture the statistics lack: a project engineer born in the 1990s, Bai Lin, checking the dam's face joints with calipers and telling his team that "an error of half a millimeter could matter to a dam meant to stand for a century."
The third unit comes next; with it, the dam takes up its full load — power, irrigation, and the Tarim's yearly ecological supply — in a region whose binding constraint, as the project's own coverage keeps repeating, is not land but water.