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  3. Removing Dams P1: In the last century, many of the dams in the United States were built for water diversion, agriculture, factor

Removing Dams P1: In the last century, many of the dams in the United States were built for water diversion, agriculture, factor

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问题 Removing Dams
P1: In the last century, many of the dams in the United States were built for water diversion, agriculture, factory watermills, and other purposes that allowed farming on lands that would otherwise be too dry, with low-cost hydroelectric power generation being a very significant side benefit. Building these dams was rather labor-intensive, which created jobs for workers and stimulated regional economic development. But those opposed to large dams can marshal a sobering array of criticisms based on those already built, which have provided some benefits but have without exception destroyed river environments and the human communities that depend on them.
P2: Many, perhaps most, of the more than 90,000 dams in the country are now obsolete, expensive, and unsafe, and were built with no consideration of the environmental costs. As operating licenses come up for renewal in 1999, habitat restoration to original stream flows will be among the options considered. As these dams age and decay, they can also become public safety hazards, presenting a failure risk and a dangerous nuisance. Worse still, with the growth of the American population, more people are moving into risky areas. Dams that once could have failed without major repercussions are now upstream of cities and development. In 1998, the Army Corps announced that it would no longer be building large dams. In the few remaining sites where dams might be built, public opposition is so great that getting approval for projects is unlikely.
P3: For many years, the United States Fish and Wildlife Service had advocated the removal of the Edwards Dam, which was built in 1837 on the Kennebec River in Augusta, Maine, to ease navigation and generate electricity. The Kennebec River was once home to all ten species of migratory fish native to Maine, along with several thriving commercial fisheries. Damming the river not only transformed the natural landscape, but it also prevented migration of salmon, shad, sturgeon, and other fish species up the river.
In 1999, the Federal Energy Regulatory Commission (FERC) refused the renewal of the dam license due to excessive negative environmental impact, and the dam was removed, freeing a 17-mile stretch of the Kennebec River that had been submerged for 162 years. P4: The cost of keeping outdated hydroelectric equipment running decades after it was installed or upgrading dam safety systems may not be worth it. This was proven true on the Elwha River in the Olympic National Park in Washington when an extraordinarily rich salmon habitat was being disrupted by an outdated hydroelectric plant. Before dams were built on the Elwha River, 400,000 salmon returned each year to spawn, but that number dropped to fewer than 3,000 after dams were put up. Once the hydroelectric power generating capacities of the dams had outlived their useful lives, the importance of this salmon habitat necessitated the removal of the dams on the Elwha River. Simply removing the dams will not restore the salmon, however. Where 50-kilogram king salmon once fought their way up waterfalls to lay their eggs in gravel beds, there are now only concrete walls holding back still water and deep beds of muddy deposits.
P5: When the negative environmental effects outweigh the benefits, a dam may be considered for removal. The Hetch Hetchy Dam, whose construction was one of the first major defeats of the nascent American environmental movement, was approved in 1913 to assist earthquake-ravaged San Francisco. Environmentalists and nature lovers, who said the valley’s beauty surpassed even Yosemite Valley’s, have constantly fought for its removal. They claim that restoring Hetch Hetchy Valley could reclaim an area that is half the size of Yosemite Valley and nearly identical in terms of beauty. Revenue and increased local spending from tourism could offset some or all of the losses from removing the dam. This problem can be thought of as appraising the relative value of two scarce resources, water and space, in Yosemite National Park.
P6: How does one weigh the many different economic, cultural, and aesthetic considerations for removing or not removing these dams? Do certain interests, such as the rights of native people or the continued existence of native species of fish or wildlife, take precedence over economic factors, or should this be a utilitarian calculation of the greatest good for the greatest number? And does that number include only humans, or do other species count as well?
P4: ■ The cost of keeping outdated hydroelectric equipment running decades after it was installed or upgrading dam safety systems may not be worth it. ■ This was proven true on the Elwha River in the Olympic National Park in Washington when an extraordinarily rich salmon habitat was being disrupted by an outdated hydroelectric plant. ■ Before dams were built on the Elwha River, 400,000 salmon returned each year to spawn, but that number dropped to fewer than 3,000 after dams were put up. ■ Once the hydroelectric power generating capacities of the dams had outlived their useful lives, the importance of this salmon habitat necessitated the removal of the dams on the Elwha River. Simply removing the dams will not restore the salmon, however. Where 50-kilogram king salmon once fought their way up waterfalls to lay their eggs in gravel beds, there are now only concrete walls holding back still water and deep beds of muddy deposits.
An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Drag your choices to the spaces where they belong. To review the passage, click on View Text.
Many dams were built in the United States during the last century, and they provided a broad range of economic benefits.
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Answer Choices
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 dam on the Elnha River and the Hetch Hetchy Dam in the valley.
C The removal of dams remains controversial because of complex factors that are involved in weighing their advantages and disadvantages.
D Since the late 1990s, dams constructed without considerations for environment costs, especially those negatively impact human and aquatic creatures, have been considered to remove.
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.
选项
答案A，C，D
解析 【文章总结题】本文主要讲了20世纪美国的大坝，大坝具有提供低成本的水、电，促进经济发展等优点，但是建造大坝带来的问题也很严重；20世纪90年代末，一些危害性很大的水坝被建议拆除：但是是否拆除一个大坝是非常复杂的事，因为涉及多个影响因素。因此涉及美国大坝优缺点及是否拆除问题的A、C、D选项正确。B、E、F三个选项属于细节偏离主旨，或者与文章内容不一致。
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