Wu River (Yangtze tributary)

The Wu River is the largest southern tributary of the Yangtze River. Nearly its entire length of 1150 km runs within the isolated, mountainous and ethnically diverse province of Guizhou. The river takes drainage from a 80300 km2 watershed.

The river flows through the Liupanshui, Anshun, Guiyang (the capital), Qiannan, and Zunyi Districts of Guizhou. All nine regions of the province have at least partial drainage to the river.

Course
The river begins as the Sancha in western Guizhou and flows eastwards about 350 km. It then bends north, west and south in a 300 km reach called the Yachi, and receives the Nanming River from the right. After the Yachi reach, the Wu makes a broad arc northeast through central Guizhou, picking up fifteen major tributaries including the Yu, Furong and Ya Rivers and flowing through several large hydroelectric dams. It then crosses the border into the provincial-level municipality of Chongqing, flows past Wushan, Badong and Zigui, and empties into the Yangtze River at Fuling, some 50 mi east-northeast of Chongqing, in the Wu Gorge of the Three Gorges of the Yangtze. Part of the lower course of the river is flooded by the reservoir of Three Gorges Dam.

History
Many small river towns along the Wu, such as Gongtan, date back to as early as 200 A.D. Fuling is regarded as the first major town to be built on the river. The city was the capital of the ancient Ba state in the Sichuan area. During the Qin Dynasty, the region was brought under Chinese control.

The Wu Gorge is also known as "Golden Helmet and Silver Armor Gorge". The name originates from a helmet-shaped rock formation above the river and a silver-colored cliff of slate. Another name for Wu Gorge is "Iron Coffin Gorge".

River modifications
The Wu River has been extensively developed for hydroelectricity generation. , dams along the river had a combined capacity of 8,500 megawatts (MW). Much of this development is extremely recent, as power generation in 2010 was over four times of that in 2005. Most dams on the river were constructed and owned by the Wujiang Hydropower Corporation. The largest dam, the 232 m Goupitan Dam, was completed in 2011. Aside from producing power, dams on the Wu River also provide flood control and hydraulic head for irrigation operations.

The lower reaches of the river are heavily polluted because of poor sewage systems and dumping of agricultural waste – so much that it is not even considered suitable for irrigation and industrial purposes.

About 40 km of the river's lower course forms an arm of the Wu Gorge (Big Gorge or Second Gorge) of the Three Gorges, now submerged in up to 30 m of water from Three Gorges Reservoir. In late 2008, geological instabilities caused landslides with volumes of 20000 and 50000 m3. It is speculated that the former slide is part of a larger unstable slope with as much as 100000 m3. The latter slide caused a wave that swamped boats up to 2 km away.

The 10 dams on the river that are either completed, under construction or planned,, are listed below from downstream to upstream.
 * Daxikou Dam – Cancelled, 1,200 MW
 * Baimato Dam – Programmed, 350 MW
 * Yinpan Dam – Completed, 600 MW
 * Pengshui Dam – Completed, 1,750 MW
 * Shatuo Dam – Completed, 1,120 MW
 * Silin Dam – Completed, 1,050 MW
 * Goupitan Dam – Completed, 3,000 MW
 * Wujiangdu Dam – Completed, 1,250 MW
 * Suofengying Dam – Completed, 600 MW
 * Dongfeng Dam – Completed, 695 MW

Navigation
In the 1950s, local governments began an ambitious project to increase the navigability of the Wu River. The lower 480 km of the river were dredged of sediment and hundreds of sets of rapids were destroyed by explosive charges. Navigation on the upper river, in contrast, reflects the difficulty of traversing the Yangtze in the Three Gorges region before the construction of Three Gorges Dam. With the creation of the reservoir behind this dam, navigation on the lower reaches of the Wu has increased significantly.

Bridges
There are many spectacular bridges along the course of the Wu River. These include (from mouth heading upstream):
 * Fuling Arch Bridge
 * Fuling Wu River Bridge
 * Jiangjiehe Bridge
 * Zunyi Bridge
 * Wujiang Viaduct
 * Liuguanghe Xiqian Expressway Bridge under construction
 * Liuguanghe Bridge
 * Yachi Railway Bridge under construction
 * Yachi Bridge
 * Najiehe Railway Bridge
 * Dimuhe River Bridge