Dams are widely distributed throughout the U.S. Their impact is perhaps most apparent in western cities, many of which lack a sufficient local ...
KTEH Public Television and Sony Pictures Television
Original program ©1997 Public Television Station KTEH. All rights reserved. A Co-Production of Trans Pacific Television and KTEH. Courtesy of KTEH Public Television and Sony Pictures Television. Teachers' Domain version ©2006 WGBH Educational Foundation. All Rights Reserved.
Assessing the value of dams is a complex matter. Damming can serve many of society's needs, especially those of a thriving community or region. For example, water released from reservoirs that form upstream from a dam can be used to generate electricity. By smoothing out the natural, seasonal variation in water flow, dams also provide a reliable water supply to regional populations, help reduce the risk of floods and droughts, and provide recreational opportunities.
However, there are also many reasons not to build dams. For example, the presence of a dam and the regulation of water flow greatly reduce the amount of sediment carried by the river. Such sediment creates riverside beaches and coastal wetland features like marshes that provide habitats for many animals and plants. In addition, some native fish species are unable to adapt to the unusually cold water released by the dam, or to pass these huge blockades to return to upstream spawning grounds. Upstream, the artificial lakes that dams create can destroy entire canyon ecosystems when the canyon fills with water and, ultimately, too much sediment. The pressure to preserve rivers in their natural, or wild, state has led to the decommissioning of several large dams and has thwarted plans in many states to build new dams.
In the early 1980s, population growth in Denver and the surrounding areas created a need for additional water supply. However, a proposed dam that would have enabled the city to store water for longer-term use met with opposition from local citizens, fishermen, and environmental groups. In 1990, President George H. W. Bush vetoed the plan for Two Forks Dam. As an alternative to the dam, opponents urged residents, businesses, and the city itself to conserve the water they already had.
Water-conservation initiatives like those described in this video segment have been tried successfully in Denver and elsewhere. Although the pressures of population growth and short supply continue — and are likely to continue for some time — it's clear that, dams or no dams, conservation is a necessary component of any overall water management strategy.
- How do dams benefit people? How may they be harmful?
- The narrator says that the era of building dams in the United States is coming to a close. What are some reasons that big dams are less likely to be built today than in years past?
- How does Denver encourage the conservation of water?
- What are two ways you can conserve water where you live?