President Obama will propose a reduction in U.S. greenhouse-gas emissions “in the range of 17%” during a United Nations climate-change conference on Dec. 9, the White House announced on Nov. 25. The proposal that Obama will offer at the meeting, to be held in Copenhagen, would trim emissions in 2020 about 17% from 2005 levels. The climate-change bill that the House passed in June also calls for a 17% cut.
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.