Basic Concepts and Management Issues of Rivers - River Dynamics and Integrated River Management - page 42

For reservoirs on rivers with high sediment concentration and low water runoff drawdown flushing
and empty flushing are applied. Low-level outlets are open in the flood season to drawdown or empty the
reservoirs and create riverine flows along the impounded reaches, which scour and release the sediment
deposited in the reservoirs. Retrogressive erosion is induced by drawdown and empty flushing, which
may extend the flushing far upstream of the dam. The Hengshan Reservoir on the Changyuan River in the
Shanxi Province is a gorge type small reservoir with a capacity of about 13 million m 3 . The area is arid
and there is almost no flow in the non-flood seasons. The reservoir was used to store water during the
flood season and provide water for irrigation in the non-flood seasons. It was silted up quickly in the first
8 years of operation and 30% of the capacity was lost due to sedimentation. Then, the reservoir was emptied
for flushing of sediment in the flood seasons of 1974 and 1979. Consequently, about 2 million m 3 of its
capacity was regained.
The Three Gorges Project (TGP) on the Yangtze River is the largest reservoir in China with the highest
power generation capacity in the world. Problems and strategies related to the project are discussed in
Chapter 7.
1.2.7 River Uses
1.2.7.1 Hydro-Power
By the end of 1999, the total installed capacity for hydropower in the country amounted to 70,000 MW
with an annual energy output of 210 trillion Wh, which ranked second and third among all the countries in
the world, respectively. There are about 220 large- and medium-sized hydropower stations either completed
or under construction at present, in which 20 have an installed capacity of more than 1,000 MW, 37 have
an installed capacity of more than 500 MW; and 53 have a dam higher than 100 m. (IWHR, 2000)
During the 1950s, the first large-sized hydropower station, Xin'anjiang was constructed, with a dam
height of 102 m and an installed generating capacity of 662.5 MW. After that a cascade of hydropower
development was carried out for the medium and small rivers of Xinfeng in Guangdong province, Zhexi
in Hunan province, Yili in Yunnan province, Maotiao in Guizhou province and Yongding in Beijing.
During the 1960s, a number of large- and medium-sized hydropower projects were constructed, such
as Liujiaxia in Gansu province (installed capacity 1,160 MW), Danjiangkou in Hubei province (900 MW),
Zhexi in Hunan province (447.5 MW), and Yunfeng on the Yalu River (400 MW). During the 1970s, the
hydropower projects of Fengtan in Hunan province (400 MW) in Liaoning Province, Bikou in Gansu
province (330 MW), Gongzui in Sichuan province (700 MW), and Qingtongxia on the Yellow River
(272 MW) were constructed.
During the 1980s, construction of hydropower projects was carried out on an even larger scale. The
Wujiangdu in Guizhou province (630 MW), Baishan in Jilin province (900 MW), Longyangxia in Qinghai
province (1,280 MW), Dongjiang in Hunan province (500 MW) and Gezhouba on the Yangtze River in
Habei province (2,715 MW) were completed and put into operation. (IWHR, 2000)
During the 1990s, the improvement of managerial institution for the development of hydropower
resources greatly accelerated the development of hydropower and the construction periods for the main
structures of large-sized hydropower stations were generally reduced by 1-2 years in comparison with the
past, with the examples including the Lubuge, Guangxu I, Shuikou, Geheyan, Yantan, Manwan, Wuqiangxi,
Lijiaxia, Tianhuangping, Shisanling, Lianhua, Ertan, and Tianshengqiao Hydropower Projects. The
construction of pumped-storage power stations also saw great progress, and the completed ones include
the Guangzhou Project in Guangdong province (2,400 MW), Shisanling Project in Beijing (800 MW),
and the Tianhuangping (1,800 MW) and Xikou Projects in Zhejiang province (80 MW).
In China, the total installed capacity rose from 65.9 GW in 1980 to 236.5 GW in 1996 and 254.2 GW
in 1997, a rate of increase that lagged behind that of gross domestic product (GDP) although still a relatively