I've visited several controversial (有争议的) dam sites around the world. For all of them, the tension has been between the national economic advantage offered by the dam and the local environment and social damage caused by its construction. The countries often sell the power to international neighbors, rather than directly improve electricity access to the local people.
Some countries, such as Chile, which is planning to build a dam across Patagonian Rivers, and Laos, which plans to dam the Mekong, rely on energy imports and so hydro (电能) is a very attractive domestic option. Other countries, such as Brazil which is planning the world's third largest dam at Belo Monte, China which recently completed the largest dam at Three Gorges, and Ethiopia which is planning dams along the Omo, insist that these dams are essential for national economic development.
The economic benefits can be huge. The Aswan Dam on Egypt's Nile, for example, was highly controversial when it was built in the 1960's. Yet for all the environmental damage to its downstream river system, it's very difficult for you to find an Egyptian that is in favor of its removal. The dam has been an outstanding economic success, bringing improved harvests from better irrigation despite drought conditions, hydropower and flood protection worth billions of dollars.
So if we accept that many controversial dams are going to be built, how can we limit their damage? Jamie Skinner, who was senior advisor to the World Commission on Dams, and now heads the Water division at the International Institute for Environment and Development, suggests the answer might be to issue dam builders with limited-length licenses. "In America, the licenses are only for 30 or 50 years, after which there is a review. The reason why many dams are being removed there now is that their licenses have expired (到期) and the dams would no longer pass the stricter environmental planning regulations." he says.
