Hydro dams are threatening large rivers, says WWF

GLAND, Switzerland, 2004-06-30 (Refocus Weekly)

Indiscriminate building of dams is threatening the world’s largest and most important rivers, according to a new report from the World Wildlife Federation.

More than 60% of the world’s 227 largest rivers have been fragmented by dams, leading to the destruction of wetlands, a decline in freshwater species and the forced displacement of tens of millions of people, says ‘Rivers at Risk’ which examines the top 21 rivers at risk from dams being planned or under construction. The Yangtze in China, the La Plata in South America, and the Tigris and Euphrates in the Middle East are likely to suffer the most from dams.

“Dams are both a blessing and a curse - the benefits they provide often come at high environmental and social costs,” says Ute Collier of WWF’s Dams Initiative. “Those most affected by dams rarely benefit from them or gain access to power and clean water.”

The Yangtze is the river at most risk with 46 large dams planned or under construction, with the Three Gorges Dam causing 1.3 million people to lose their homes and destroy the habitat of many endangered aquatic species, it claims. The Danube and Amazon rivers are included in the list, as are the Ganges and Mekong.

Downstream communities suffer most from dams, with dry rivers and decimated fish stocks, it claims. Dams disrupt the ecological balance of rivers by depleting oxygen and nutrients, which affects migration and reproduction of fish and freshwater species.

The analysis examines dams that are at least 60 m high or installed capacity of at least 100 MW. It includes dams for power, irrigation, water supply and flood prevention.

Governments are not applying the recommendations of the World Commission on Dams to their dam projects, it adds, and the benefits from dams are often overtaken by negative environmental and social impacts. Much of the water from dams is lost, mainly due to inefficient agriculture irrigation systems, it adds.

“Dam construction projects often proceed with little attention to cumulative impacts and alternatives,” says Collier. “In meeting growing global water and energy needs, we must not destroy the ecosystems that provide clean and sustainable water supplies.”

Dam construction has shifted from the developed to the developing world, with China and India implementing large dam construction programs that threaten the risk to ecosystems. “The environmental impacts associated with large dams are well documented, and recently there has been an increased emphasis on the social and economic effects of these environmental impacts,” which vary in extent and gravity, it explains. Sediment retention can interfere with dam operations and shorten their intended lifespan, with 2 km³ of reservoir storage capacity lost each year in the U.S. at a cost of US$819 million annually.

The report was produced with the World Resources Institute.


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