Why some native fish in the upper Colorado River basin are endangered (Continued)

Water development

Human population growth since the turn of the century has created a significant demand for water and hydroelectric power in western states. To meet that demand, hundreds of water projects, including dams, canals and irrigation projects, have been constructed on the Colorado River and its tributaries. Water projects have restricted the fish to about 25 percent of their former range and have blocked some of the spawning migration routes of the Colorado pikeminnow and other species. Also, tailwaters six to 20 miles downstream from dams can be as much as 15 degrees colder than the rare fishes' preferred habitat. Downstream of Lake Powell, dams have segmented the once free-flowing, silty and warm waters of the Colorado River into a series of lakes connected by cold, clear waters.

The remaining habitat has been changed considerably. The number and size of life-supporting wetlands has been cut dramatically across the nation. According to a 1990 U.S. Fish and Wildlife Service Congressional report on wetlands, over the last 200 years Colorado has lost an estimated 50 percent of its wetlands; Utah has lost roughly 30 percent; and Wyoming, about 38 percent. In the upper Colorado River basin, stream-side wetlands have been drained or cut off from the river by dikes, and many of the rivers' "backwaters" have disappeared. Young native fish have depended on these areas, which enable them to grow significantly faster and which provide warmer, slower-moving water chock-full of microscopic food.

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Endangered Colorado River basin fish Historical perspective on these fish Why these fish are endangered Upper Colorado River Recovery Program Improving habitat for the fish
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