At the December 6, 2006 meeting of the Adaptive Management Working Group (AMWG), a spring flood flow was considered for the Colorado River in Grand Canyon National Park below Glen Canyon Dam. The proposed experimental flood for sediment redistribution in Grand Canyon during the month of March 2007 was rejected after consideration. The Working Group's purpose is to balance the competing interests of power, recreation and environmental concerns in the management of Glen Canyon Dam's water releases to protect and enhance the natural resources of Grand Canyon National Park.
The intent of the flood is to transfer sand from the river bottom onto the shores of the river by releasing about 42,000 cfs (cubic feet per second) from Glen Canyon Dam. Since the operation of Glen Canyon Dam began in 1963, the sediment needed to naturally replenish beaches in Grand Canyon has been trapped behind the dam. The natural deposition of sandbars in the river's eddies provided nursery habitat for spawning fish, now endangered. Additionally, wind blown beach sand enhanced dunes that can help protect cultural sites from degradation by natural erosion. Proponents of the flood hoped that it would mimic these natural processes.
During a presentation by the Grand Canyon Monitoring and Research Center (GCMRC) at the meeting, it was estimated that severe rainstorms in the fall of 2006 placed 1.5 to 2.6 million tons of fine sediments into the Colorado River below the dam. The Center predicts that most of the existing sand in the Grand Canyon will eventually be transported and deposited into Lake Mead, the reservoir downstream of Grand Canyon.
Experiments proposed by the GCMRC would include evaluating how the flood would affect the aquatic food web of the river, and determining the success of moving sand to the lowest reaches of the canyon. Previously most of the sediment has been stored in the upper reaches near the mouths of the Paria and Little Colorado Rivers.
Since some of the flow in a simulated flood comes from the dam's bypass tubes that do not spin generators to make electricity, the majority of AMWG representatives felt that the experimental flow would decrease hydropower revenues. Other Working Group members felt that the high flows would harm the non-native trout populations and the aquatic food web. Also, the short time frame for adequate planning and obtaining required environmental clearances caused concern within the group. Scheduled generator maintenance at the dam prevents an experimental flood after March of 2007.
Despite ten years of experimentation, all efforts of the Adaptive Management Program have so far failed to protect the dwindling resources of the Grand Canyon. "If Glen Canyon Dam continues to operate as in the past" notes John Weisheit, Conservation Director of Living Rivers, "the lack of adequate sediment combined with lack of substantial flood flows (over 65,000 cfs) doom the Working Group's efforts to failure. The only alternative that will truly protect the Grand Canyon is the decommissioning of Glen Canyon Dam. Anything less is ‘fiddling while Rome burns'."