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Nature demands her share Glen Canyon Dam changed that. Once the water is impounded behind the giant concrete structure, the silt and sediments settle. The water temperature drops as the lake deepens. By the time it passes through the power turbines at the dam, it is cool and clear. That's not good for the native fish species, which like warm, muddy water, but it's ideal for non - native trout, which like to eat native fish. The population of the endangered humpback chub, a fish that evolved over millennia and lives only in the lower Colorado River, has fallen by nearly 70 percent since 1989, and scientists blame the dam. Federal officials launched an adaptive management program nearly a decade ago to try to help the fish and other species. A key was to mimic the river's old flow patterns and move sediment. In 1996, then - Interior Secretary and former Arizona Gov. Bruce Babbitt oversaw an engineered flood, which was meant to move sediment and help rebuild beaches and restore fish habitat. That experiment is now considered largely unsuccessful, but others have followed, including the removal of trout from areas where chub live. Nikolai Ramsey works for the Grand Canyon Trust, a conservation group working to protect the Colorado River's geologic masterpiece. He is the group's representative on a regional committee that evaluates the adaptive management program. Ramsey works in Flagstaff, a steep 130 -mile drive from the dam, but he shuttles among Flagstaff, Page, Phoenix, Salt Lake City and the Grand Canyon often and has watched the work up close in the Canyon. He still believes it's possible to manage the river for human use and still find ways to protect endangered species and habitat. "There is some human arrogance on our part in thinking we can manage the river by mimicking natural conditions," he said. "But we can take a shot. Let's push the science as far as we can and have the science drive the management actions. Let's see if we can't have both the conserving of the human values that derive from the dam being there and also the environmental values. We still think that's possible." He said the idea of removing the dam is not without logic, but the political and practical realities are that it's there "and it does achieve its purposes." Environmental shims Along the receding shorelines of Lake Powell and Lake Mead, biologists are watching the effects of the drought as it reveals long- buried box canyons and takes water back from marshes and inlets. Already, thickets of tamarisk, a fast - spreading invasive tree, have appeared on the upper end of Lake Mead, where water levels have dropped dramatically. Tamarisk, also known as salt cedar, can kill out native plant species, but it also provides an attractive nesting spot for birds, including the endangered Southwestern willow flycatcher. That happened at Roosevelt Lake northeast of Phoenix, and the lake's operator, Salt River Project, was forced to spend millions of dollars to create a new nesting area for the bird. Without that habitat plan, SRP could not allow those areas of the lake to be inundated with water once lake levels began to rise again, eliminating critical water storage. "That could happen up there, but we can't really predict it," said Lesley Fitzpatrick, a wildlife biologist for the U.S. Fish and Wildlife Service. "it would depend on how fast the trees grew and how long the water stays low. It happened over a long time at Roosevelt." Early surveys haven't turned up any flycatchers in either reservoir, but Fitzpatrick said she has seen other changes. Habitat has dried up in some places, forcing birds and other wildlife to move on. In some ways, she said, the ebbing and flowing of the lakes mimic the old river, exposing habitat and then drowning it again later, but "the scale is different and the timing is different." Page 4of5 http:// www. azcentral .comispecialslspecia1061 articles /0722colorado- environment.html 7/27/2004