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The turbulent upper Huang He meanders east through a series of gorges to the fertile Lanzhou valley. Hydroelectric power dams in the Liujia gorge and at Lanzhou, the largest city on the river, generate electricity and impound irrigation water. Past Lanzhou, the Huang He becomes a wide, slow-moving stream as it begins its bend around the Ordos and separates the northern uplands from the desert and loess lands of the south and west. It is navigable in places for small vessels. The west end of the "great northern bend" passes through the heavily populated Ningxia agricultural region, an oasis c.60 mi (100 km) long, where cereals and fruits are raised. At the northwest corner of the "great northern bend," the Huang He divides into numerous branches, watering a fertile area where ancient irrigation canals have been repaired and are now in use. At the northeast corner lies the most fertile land outside the Great Wall; it was farmed without irrigation until 1929.
Turning south, the Huang He passes through the Great Wall and enters the fertile loess region (where rich coal deposits are also found on both sides of the river). Cutting deep into the loess, the river receives most of the yellow silt from which its name is derived. After receiving the Wei and Fen rivers, its chief tributaries, the Huang He turns east and flows through Sanmen gorge, site of the Sanmenxia dam, which is used for power production, flood control, and navigation. Below the Sanmenxia dam is the multipurpose Xiaolangdi dam, located in the river's last valley before the North China Plain, a great delta created from silt dropped at the Huang He's mouth over the millennia. The North China Plain extends over much of Henan, Hebei, and Shandong provs. and merges with the Chang (Yangtze) delta in N Jiangsu and N Anhui provs. The Huang He meanders over the fertile, densely populated plain to reach the Bohai. The plain is one of China's most important agricultural regions, producing corn, sorghum, winter wheat, vegetables, and cotton.
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