Science As It Happens - Thursday March 06, 2008
Aerial picture of Glen Canyon Dam’s four open jet tubes on March 6, 2008, during the high-flow experiment. Photo: Matthew Andersen, U.S. Geological Survey.
Impressions at Glen Canyon Dam
A visit to Glen Canyon Dam, located near Page, Ariz., on March 6, 2008, provided a great deal of stimulation for my ears and eyes. As someone who has visited the inside of the dam only a few times, I found the sensory contrasts as I moved through the dam to be dramatic.
As my escort and I made our way through tunnels and elevators to reach the bottom of the dam, we held our voices low, but the tiled surfaces made our voices echo slowly back to us, with words returning long seconds after they were first spoken. Once at the bottom of the dam, we proceeded through more tunnels toward the face of the dam, and the noise started to increase, first when we passed by the big lawn covering the earthen confines of the penstock tubes, then as we passed through the large open generator viewing room, where the generators were humming along. None of this volume, however, compared to stepping out into the bright sunlight and hearing the roaring jet tubes. The late winter sunlight shone directly down on us, refracted and magnified through the spray of the water that flew from the tubes. We stepped over to the edge of the dam, and I could see the four open jet tubes shooting water nearly halfway across the width of the river. The smooth arc of the dam, its margins and seams as crisp as the pleats of Dwight Eisenhower’s campaign jacket, gazed passively down on the boiling, rumbling, churning water below.
To get closer to the tubes, we stepped back into the cool morning shadow created by the eastern canyon wall. The transformers were humming like hundreds of synchronized cicadas, transporting freshly generated power up the lines to the transmission towers high above. As we approached the tubes, I could start to feel the rumble of the river passing through the constraints of the dam in my feet and legs.
The plume of water created by the water released from the open jet tubes as it collides with the Colorado River. Photo: Matthew Andersen, U.S. Geological Survey.
The view of the released water up close was very impressive. Continuous massive cannon bursts of water shot from the tubes. Although the water appeared very uniform and constrained immediately after leaving the tubes, it quickly disintegrated into chaos, forming big billows of water and mist, churning first through the air, then down into the river where more water and spray was released by the descending volume. Some dark plumes of sediment were visible in the spray as it churned back up into the air.
We stepped back into the base of the dam, leaving the thundering water behind. Now new noises could be heard. Our hardhats and earplugs seemed trivial protection against the Colorado River thundering and groaning through 15-ft diameter penstock tubes over our heads. As the water dropped out of the tubes, my escort described how it was dropping in vortices to release points under the dam. These vortices could be heard behind large steel plates held in place by massive bolts. Here again, the water would not be constrained to uniformity. I could picture enraged, confined bull elephants, kicking and swatting, creating irregular thumps against the steel plates, testing the bolts. The thumps were easily audible despite my ear plugs. All of the rushing water made the solid-looking concrete floor rumble, creating the distinct impression of an impending earthquake. It was not a comfortable place to be. My escort assured me that this was not a normal day at the base of Glen Canyon Dam. We re-traced our steps, and soon we were back in the Carl Hayden Visitors Center.
I passed through the quiet of the bookstore. Now there were more security and Natural History Association employees than visitors, a dramatic contrast to the hectic day before when so many visitors, dignitaries, officials, and members of the media had been passing through.
On my way back to Flagstaff, Ariz., I stopped at the dam overlook downstream for one more glimpse of the high-flow release. The billows of water and mist down at the river were dwarfed against the red cliffs, the dam face, and the crystal blue sky. Will this clear, cold, relatively modest release help recreate more natural features and habitats downstream in Marble and Grand Canyons? Many U.S. Geological Survey scientists, including geologists, hydrologists, and biologists, are moving into the swift current today to collect the data to help answer that question. Time will tell. The experiment has begun.
Thank you very much to Ken Rice and Mike Lennon of the Bureau of Reclamation for allowing me to visit Glen Canyon Dam.
Matthew E. Andersen
Supervisory Biologist
Grand Canyon Monitoring and Research Center
U.S. Geological Survey
Flagstaff, Ariz.