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~~-; -- ~~L The experimental flood consisted of: ^ Four days of 8,000 cfs discharge for pre-flood data collections ^ Ten hours of up-ramping to fhe peak flood ^ One week of a 45,000 cfs peak ^ Stepwise down-ramping to four days of 8,000 cfs flows for post- flood data collection Colorado River: Grand Canyon, Arizona The construction of Glen Canyon dam was controversial from the outset. However, critics at the time focused attention on upstream impacts -specifically the drowning of Glen Canyon. While many still lament the loss of those sculptured canyons, recent controversy has focused on the operations of the dam and their impact on the natural and cultural resources downstream in Grand Canyon National Park. In March 1996, the Bureau of Reclamation let loose a deluge from Glen Canyon Dam. The event was the culmina- tion of a remarkable consensus process that may significantly change how we manage our western rivers. Prior to its damming, the Colorado River was dominated by variability. Flows ranged from over 120,000 cubic feet per second (cfs) in the spring to less than 1,000 cfs by late summer, and temperatures varied from 65 degrees to below freezing. When the gates of Glen Canyon dam closed in 1963, the Colorado River above and below was fundamentally altered by the removal of the system's dynamics. Once characterized by muddy, raging annual floods, the river was transformed into a clear, cold stream. Seasonal water flows were stabilized and replaced by daily fluctuations in river level of as much as 15 feet, driven by electrical demands for peaking power. A band of exotic vegeta- tion colonized a river corridor no longer scoured by spring floods. Five of eight native fishes disappeared and the broad sand beaches of the pre-dam river melted away. The dam provided financing for other reclamation projects in the upper basin states of Colorado, New Mexico, Utah and Wyoming. Utilities and commu- nities within the region came to rely on the dam's low cost power. The Experimental Flood The principal goal of the experimental flood was to restore disturbance and dynamics to the river ecosystem. Planners expected that additional sand would be deposited on canyon beaches and that backwaters, important rearing areas for native fish, would be revitalized. They also hoped that new sand deposits would stabilize eroding cultural sites and that the high flows would flush some of the exotic fish species out of the system. Despite being limited to a magnitude of less than half the annual pre-dam floods, the experimental flood was successful. Over 55 new sandbars were created and the majority of existing sandbars were enhanced; few decreased in size or volume. Cultural sites were stabilized, but the restoration of backwaters was less success- ful. The impact on exotic fish populations and the long-term potential for the river's native biological community remain to be determined. Success in the Process One overarching success of the experimen- tal flood of 1.996 was evident before it even started: the unprecedented flood took place in an atmosphere of consensus and without litigation. This success was the result of a six-year process led by the