TOEFL Reading: ETS-TOEFL阅读机经 - 6JW4645Y3W3B1M3DL$

Many dams were built in the United States during the last century, and they provided a broad range of economic benefits. A. Until recently, the emphasis in dam building was on the economic benefits of low-cost energy and water that dams provided, but more attention is now being paid to the damage they cause. B. Environmental groups now have a very good chance of forcing the removal of two major dams, the Glen Canyon Dam on the Colorado and the Hetch Hetchy Dam in Yosemite. C. The removal of dams remains controversial because of high restoration costs, loss of low-cost electricity, and the loss of water storage facilities. D. Since the late 1990s, the government has stopped building large dams, instead focusing on removing existing dams and restoring natural habitats. E. Until recently, the main reason for removing dams was to restore salmon runs, but it is now recognized that a more important reason to remove dams is that they are no longer safe. F. Although the U. S. government originally planned to remove the Elwha and Glines Dams in Washington, the enormous expense of removal has resulted in a postponement of this effort.