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Rearranging deck chairs at Glen Canyon Dam
April 13, 2008
The experimental flood release last month from Glen Canyon Dam was merely another public relations façade staged by the Department of the Interior believing three times is a charm. Luck is not how one restores the Grand Canyon.
The first media hoopla was in 1996, then again in 2004, and now in 2008. Twelve years, three experimental floods, same results: a degraded ecosystem for this prized national park. These experiments do nothing but rearrange the furniture and most of the shuffling occurs in Marble Canyon, which is the first 61 miles of Grand Canyon National Park.
Sometimes mistakes occured, such as the 2004 high flow test which, due to circumstances revolving around logistical problems, prevented any gains in scientific knowledge concerning the biological resources threatened by the fluctuating hydropower flows from Glen Canyon Dam.
How much sand has been removed from Marble Canyon since operations at Glen Canyon Dam began? According to the USGS, 16,000,000 metric tons of sand were initially scoured away in the spring months of 1965 (two years after the the initial filling Lake Powell began) between the Lee's Ferry gage (Mile 0) and the gage at Phantom Ranch (Mile 88) (Rubin, 2001). These clear water dam releases peaked at 58,100 cfs on June 13, 1965.
You can view the historic data of Lake Powell here once power generation began, upon reaching the minimum pool elevation of 3490 feet above sea level, and also during the snow melt of 1965.
During the initial filling of the reservoir, and to provide water for downstream use at the same time, the concrete plug in the left diversion tunnel was designed to bypass water through 3 steel gates (photo) that could be operated from a chamber that had access from the dam superstructure (see page 42: dam construction and specifications). After the reservoir reached the level of the penstocks to commence power generation, and the testing of the various waterworks, the bypass gates and chamber were back-filled with concrete on July 7, 1965.
The reduction of sand since the scouring event of 1965 in Marble Canyon has been 6,000,000 metric tons (Wright, 2008), and this removal rate remains ongoing despite the sand conservation mandate of the Grand Canyon Protection Act of 1992.
Even if Interior began to operate the dam with the single purpose of rebuilding the beach and habitat conditions as they existed in 1992, it would take 40 to 45 years to achieve this goal, they say. The odds are clearly against the status quo player.
To view photos of beaches near the time of Glen Canyon Dam construction and after the 2008 experimental flood click here.
To view photos of beaches as they appeared in 1889 click here and search for photographs of Grand Canyon by Robert Brewster Stanton.
Why is this charade tolerated? Why does Interior continue to stage farcical media sensations instead of providing results that are tangible and real?
The scientists explained in 2005 that the sand replenishment hypothesis from the 1995 EIS is flawed. The scientists recommended that mechanical sediment augmentation may need to be implemented afterall.
To view photos of the sediment accumulation occurring at Lake Powell, click here.
To view satellite imagery of Lake Powell sediment, click here.
It is clear: there will never be enough sediment for the ecosystem until different applications are seriously examined. Namely, mechanical sediment augmentation and restoring a free-flowing river through Grand Canyon by dismantling Glen Canyon Dam.
Scientists noted how a change in climate patterns (the intensity of summer storms have decreased overall) occurred around 1940. From 1941 to 1957, the annual sediment load in the river dropped to 85 million tons. 1957 is the year that the upper Colorado River basin dam construction began. These reservoirs now intercept the sediment load of the Colorado River basin. The flow of sediment that enters Lake Powell is now 44 million tons annually.
Click here to read a science article about sediment.
Click here to see what happens to a sediment-choked reservoir in flood stage.
Very few people have seen Cataract Canyon above Lake Powell. Those who have, like myself, will tell you how the sediment passing through Cataract Canyon creates ample beaches and sandbars every year. And yes, Cataract Canyon has endangered species too, but at least they are not extirpated (regionally extinct) like they are in Grand Canyon. Scientists are not studying Cataract Canyon sediment dynamics at all, even though the National Research Council has advised they do.
As of September 9, 2008 and reported by the Associated Press, the sandbars created by the experimental flood last March have eroded away.
Watch this time-lapse photography of eroding sandbars.
Sediment Response to Construction and Recent Adaptive Management of Glen Canyon Dam, Colorado River, Arizona. Booth, 2005.(cache)
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