Flushed With Success The Report Card Isn't Quite In, But The Great Grand Canyon Flush Of '96 Appears To Be A Success. By Gregory McNamee Q: WHAT DO YOU do with a long-dammed river whose channel is choked with silt? A: Flood it. Which is precisely what the Bureau of Reclamation did during a two-week experiment last spring that sent 117 billion gallons of water from Lake Powell roaring through the upper reaches of the Grand Canyon. The river in question was the Colorado, the dam Glen Canyon, built amid great controversy in 1963. In addition to forcing accumulated sediments downriver--where they would have traveled naturally had the dam not been there--the flood carved out a series of new beaches, which may provide expanded habitat for area wildlife. The river normally flows at a controlled rate of about 10,500 cubic feet per second (cfs), but the flood came down as fast as 45,000, and stir things up it did. According to the experiment's designers, the release--conducted at a reported cost of nearly $75 million--was an unqualified success, so much so that Interior Secretary Bruce Babbitt was moved to remark, "These early results confirm our conviction that a new era has begun in the management of the Colorado River and the Grand Canyon." An initial Bureau of Reclamation report, released late in May, says the flood created more than 55 beaches alongside the river, most within the 62 miles from Glen Canyon Dam to the confluence of the Colorado and Little Colorado rivers. Using computer simulations, geologists had modeled comparatively slow changes to the riparian environment in the wake of the flood; but, as the report notes, they were surprised to find some 80 percent of the new beaches and sandbars formed during the first two days. Explains Tucson-based United States Geological Survey scientist Julia B. Graf, "The release showed us things happen very quickly in floods." (Project scientists have not yet tabulated the flood's effects farther downriver; a more complete, and final, report is expected to be released early in 1997.) Built from nutrient-rich sand that had previously covered the river channel, those beaches offer the hope of providing renewed habitat for area wildlife. The report also observes that those nutrients, along with the mostly non-native vegetation torn from the riverbanks during the course of the flooding, seem to have given the fish below the dam an uncharacteristically good feed. Those fish, the report continues, among them the endangered humpback chub and razorback, stand to benefit from a secondary result of the flooding: the formation of backwaters along the riverbank. Existing backwaters had stagnated because the low-flowing river often did not reach them; now recharged with fresh water and sediments, these backwaters, "perhaps the key habitat area for fish species" below the dam, appear to be decidedly healthier than before. Fish were not the only beneficiaries of this revitalization; one field biologist quoted in the report observed that "peregrines were actively feeding through Marble Canyon on the birds who were feeding on the insects that were hatching due to the high flow stimulus." Finally, the report notes, an endangered gastropod, the amber snail, may have benefited from the flood as well: A particularly voracious population of deer mice that had been feeding on the snails appears to have been destroyed by the surging waters. Plans for the controlled flood began 13 years before its execution, when the results of unusually heavy flooding in the fall of 1983 alerted scientists to the possibilities of regulating the riparian environment by imitating the course of nature. That year, Glen Canyon Environmental Studies, a Bureau of Reclamation-funded study group, also set about analyzing the effects of hydroelectric power-plant releases into the river, noting the dramatic changes that occurred when those releases surpassed 33,000 cfs. Noting, however, that flood flows before the construction of Glen Canyon Dam normally reached 90,000 cfs, Graf remarks, "The river is never going to be like it was before the dam. The idea behind our experiment was not to duplicate natural floods exactly so much as to test the feasibility of controlled flooding, and, if it was successful, to establish a pattern for release." The release was not without controversy. Some environmentalists were opposed to the controlled flood because of concern that it might damage wildlife habitat harboring endangered bird species like the willow flycatcher; the report suggests that no damage occurred. Similarly, local fishing groups and river runners feared the cold-water release might harm introduced trout populations below the dam. Again, the report maintains those populations appear to have remained stable. "Without active management," the report concludes, "ecosystems like the Colorado River will continue to ecologically degrade in the face of ever increasing demands for their resources." Scientists are divided on just how that active management is to be undertaken, and especially on how often to release high flows of water from the dam. Graf believes an annual release may disturb the newly created beaches and backwaters, and she advocates less frequent releases until the long-term effects of the flood have been tracked. Susan Anderson, a Tucson-based Nature Conservancy biologist who has analyzed Grand Canyon vegetation change over the last two decades, agrees. "This is a dynamic system," she says. "There are complicated interactions, and we don't understand them perfectly. We have to get more information." Whatever the case, Glen Canyon Environmental Studies researcher Michael Kearsley volunteers, "Disturbance is the most important organizing force in riparian habitats in the desert Southwest. Even if we can only introduce a wimpy substitute for natural flooding, I think this is a good thing." Secretary Babbitt, too, holds that the controlled flood within the Grand Canyon is "a very encouraging model for restoration across the American landscape." And, echoing the conclusions of the Bureau of Reclamation report, Graf believes some of the techniques will be applied to other rivers, like the Missouri, that have been damaged by siltation and other effects of damming. "I may be a Pollyanna," she says, "but I see a situation in which we can both generate power and improve the environment."

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