Dam in USA

[box_out][box_in]Many of the dams in the eastern U.S. were originally built for water diversion, agriculture, factory watermills, or other purposes that are no longer useful. Because of the age of these smaller dams, most are now at risk for catastrophic failure or partial failure. In addition, these dams block eastern anadromous fish runs, such as those for Atlantic salmon and American shad, and prevent important sediments from reaching estuaries.

In the western U.S., most of the dams are larger projects that were built for agricultural water diversion in arid country, with hydroelectric power generation as a significant side benefit. As in the eastern U.S., the dams in the Pacific Northwest and California block passage for western anadromous fish species such as Pacific salmon and steelhead trout. Likewise, fish ladders and other passage facilities have been largely ineffective in mitigating the negative effects on local populations such as Pacific salmon, although they have worked somewhat for steelheads.

Because of these negative effects and the questionable usefulness of many dams today, widespread debates over dam removals are taking place across the U.S. While agricultural water diversion and clean, alternative energy sources are important, the safety concerns, ecosystem issues, and management expenses associated with many dams make removal the smarter option in most cases. Managers at the Bureau of Land Reclamation, which oversees most U.S. dams, need to focus on removing most of the smaller, outdated dams in the East and some of the “worst offenders” in the West.

One example of a large western dam that should clearly be removed is the 710 ft. Glen Canyon Dam in Arizona. The negative effects it has on the water quality and riparian habitat of the Colorado River in Grand Canyon National Park are nearly catastrophic. The lake formed by the dam has eliminated more than 160 miles of habitat for endangered Colorado River fish species. The reservoir also loses more than 6 percent of the total annual flow of the Colorado River to evaporation and seepage. With its size and prestige, removal of the Glen Canyon dam would be a monumental and unprecedented step toward improving much of the devastation caused by outdated and now unnecessary dams across the U.S.
Which of the following best describes the role of the last paragraph in relation to the passage as a whole?

A)It summarizes the main position of the author.
B)It provides an exception to the author’s viewpoint.
C) It exemplifies one important goal of the author.
D)It highlights the difficulties of the author’s goals.
E)It provides a broader example of the author’s position.