Zangmu Dam

The Zangmu Dam (藏木) is a gravity dam on the Yarlung Zangbo/Brahmaputra River 9 km northwest of Gyaca in the Tibet Autonomous Region of China. This dam is built a few kilometers from the Bhutan-India border. The purpose of the dam is hydroelectric power production using run-of-the-river technology. It is part of the Zangmu Hydropower Project and supports a 510 MW power station. Construction began in 2009 and the first generator was commissioned in November 2014. The last became operational on 13 October 2015. It is the first dam on the Brahmaputra/Yarlung Zangbo River and has caused controversy in India.

Background
In 1972, the Chinese Academy of Sciences created the Qinghai-Tibet Plateau Comprehensive Scientific Expedition which in part studied conditions in the Tsangpo-Brahmaputra River basin. The study concluded that 114,000 MW of hydroelectric power generation capacity could be established in the basin, 79,000 MW from the main stem alone. A more in-depth hydrological study began in 1980 which identified 12 sites for dams. It was envisioned that the dams could alleviate power shortages in Lhasa. During the 1980s and 1990s, work failed to commence in the basin. Currently, there are 28 proposed dams in the basin, Zangmu being the only one approved for construction.

In April 2009, China's Gezhouba Group was awarded a $167 million contract for the Zangmu Hydropower Project. According to the company, the contract is for the design and construction of the dam along with its power house to control water flowing downstream to North Eastern India. The project will require 3400000 m3 of concrete and 8 million tons of aggregate. Specifications for the dam are uncertain as China has not shared much information. On 12 November 2010, the construction reached coffer dam river closure. The reservoir was impounded and the first generator was commissioned on 23 November 2014. The power station was declared fully operational on 13 October 2015.

Downstream concerns
As the Brahmaputra River flows into India and Bangladesh, China's plans to construct a dam on the river are not without controversy. Reportedly, China had previously denied that they were constructing a dam on the Brahmaputra River, even after the contract was awarded. In April 2010, Yang Jiechi, their Foreign Minister, officially revealed that they were in fact constructing the Zangmu Dam on the river. China has assured India that the dam is "a small project which will not have any impact on the river's downstream flow into North-East India." Indian officials such as the Arunachal Pradesh Power Minister Jabron Gamlin express that "China's constructing a dam is a cause of concern for us, but we are not certain how big this dam is and what affect it would have on people living downstream". Reportedly, China has refused requests to reduce the height of the dam but the Indian Minister of External Affairs at the time, S. M. Krishna, had asserted that India was not concerned with the dam due to its run-of-the-river design. In January 2013 China approved three more dams on the river as part of its Twelfth Five Year Plan. The Dagu (640 MW) and Jiexu (560 MW) dams will be constructed upstream of Zangmu and the Jiacha Dam (320 MW) downstream.

Design
The Zangmu Dam is a 116 m tall and 389 m long concrete gravity-type. On its right bank is the spillway, plunge pool and bottom outlet (for silt). On the dam's left bank, the retaining dam section is 80 m tall and the power plant sits at its toe. The entire dam is 76 m wide at its base and 19 m wide at its crest. Sitting at the head of a 157668 km2 catchment area, the dam's reservoir has a daily active capacity (pondage) of 86600000 m3 and normal reservoir elevation of 3310 m. The dam's power station contains six 85 MW Francis turbine-generators for a total installed capacity of 510 MW.