Matters of Scale: Arteriosclerosis of the Earth
The following statistics are taken from: Janet N. Abramovitz, Worldwatch Paper 128, Imperiled
waters, Impoverished Future: The Decline of Freshwater Ecosystems (Washington, D.C.:
Worldwatch Institute, 1996).
- Number of large dams (at least 15 meters high) that were blocking the world's rivers as of
1950.....5,270
- Number that have been built by 1985.....36,562
- Number of large dams in China as of 1950.....2
- Number that had been built by 1985.....18,820
- Kilometers of the world's once free-flowing rivers that had been artificially altered for
navigation by 1900.....8,750
- Kilometers altered by 1980.....498,000
- Average frequency of major floods of the Rhine River in Karlsruhe, Germany (7.6 meters or more
above flood level) between 1900 and 1977.....once every 19 years
- Average frequency during the last 19 years, after extensive river engineering which eliminated
natural flood controls.....once every 2 years
- Number on salmon caught in the Rhine River (Germany and Holland) annually, 100 years
ago.....150,000
- Number caught annually by the end of the 1950's.....0
- Millions of pounds of salmon and steelhead caught in the Columbia River by commercial fishermen
in 1884.....42.2
- Millions of pounds caught in 1994.....1.2