Dams and Impounded Rivers - River Dynamics and Integrated River Management - page 392

end of 20 th century, all but 5,000 of them built since 1950. A 'large dam' is usually defined by ICOLD as
one measuring 15 m, or more from foundation to crest-(taller than a four-storey building), or with reservoir
capacity greater than 1 million m 3 . According to ICOLD the total number of large dams in 2003 is 49,697
(Jia et al., 2004). There were only eight large dams in China in 1949. From 1950 to 1990 more than 19,000
large dams were constructed. In 2003 the country has 25,800 large dams, ranking first in the world. The
U.S. is the country with the second highest number of large dams with some 8,724, followed by the
ex-USSR, Japan, and India, as listed in Table 7.1. The U.S. is estimated to have around 96,000 small dams.
If the proportion of small to large dams is similar in other countries, then at a rough estimate there are about
800,000 small dams in the world ( McCully , 1999). Figure 7.1 shows the growth curves of the number of
large dams of the world and China. From the 1970s to 2000 the number of large dams in the world and
China increase parallelly, indicating that the dam construction occurred mainly in China in this period.
T able 7.1 The first 20 countries with the most large and major dams (as defined by ICOLD)
Large dams (1986 data) Large dams (2003 data) Major dams (1994 data)
Rank Country Number Country Number Country Number
1 China 18,820 China 25,800 U.S.A. 50
2 U.S.A. 5,459 U.S.A. 8,724 CIS 34
3 CIS c. 3,000 * Japan 2,641 Canada 26
4 Japan 2,228 India 2,481 Brazil 19
5 India 1,137 South Korea 1,206 Japan 19
6 Spain 737 Spain 1,202 Turkey 11
7 South Korea 690 South Africa 923 China 10
8 Canada 608 Canada 804 Germany 9
9 UK 535 Brazil 634 Italy 9
10 Brazil 516 Albania 630 Switzerland 9
11 Mexico 503 Mexico 575 Argentina 8
12 France 468 Italy 549 India 7
13 South Africa 452 Turkey 521 France 5
14 Italy 440 UK 517 Mexico 5
15 Australia 409 Australia 474 Austria 4
16 Norway 245 Norway 336 Colombia 4
17 Germany 191 Germany 311 Iran 4
18 Czechoslovakia 146 Zimbabwe 244 Spain 4
19 Switzerland 144 Bulgaria 215 Australia 3
20 Sweden 141 Sandi Arabia 190 Pakistan 3
* The former USSR declared to ICOLD only the 132 large hydroelectric dams under the control of the Ministry of
Energy and Electrification. If the dams built by the Ministry of Agriculture and local authorities were included,
according to ICOLD, the number of large dams in the USSR should be 2,000-3,000
Source: ICOLD, 1988; International Water Power, 1995, Jia, et al, 2004
As the number of dams increased, so did their size and geographical distribution. Hoover Dam remained
the world's highest dam for more than two decades until 1957 when it was overtaken by Mauvoisin in
Switzerland. Four years later two more giants exceeded Hoover's height, Grande Dixence (also in Switzerland)
and Italy's Vajont Dam. In 1968, Hoover Dam lost its position as the highest dam in the U.S. to California's
Oroville Dam. Seven more dams in Canada, Colombia, the USSR, Mexico and Honduras overtook
Hoover in the 1970s and 1980s. The dam, which is currently the world's highest, Nurek Dam, completed