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Brent Jolley
Professor Dursema
English 1010-050
May 1, 2011
“Dammed If You Do, Dammed If You Don't”
The Colorado River has been moving sediment for years, which created one of the most
beautiful National Parks in the United States, the Grand Canyon National Park. The sediment
that was being delivered to the Gulf of California has been stopped from making the journey. It
is now being deposited in popular recreation areas known as Lake Powell and Lake Mead. The
dams holding back the water are not designed to handle the sediment that is filling up these
lakes. Sediment management is crucial, and something needs to be done to move this material
before Lake Powell becomes useless and unusable for all the resources it creates.
The source of the Colorado River is at an elevation of 9000 ft. above sea level. La Poudre
Pass Lake, located high in the Rocky Mountain National Park just west of the Continental
Divide. It travels for 1450 miles before emptying into the Gulf of California. The river has one
natural lake, Grand Lake, the largest natural lake in Colorado. It is dammed twice before leaving
Colorado. It travels through Utah picking up tributaries along the way, before it’s dammed by
Glen Canyon Dam at the Utah-Arizona border. It holds back the waters for the reservoir Lake
Powell. The river continues through Arizona and the Grand Canyon. When reaching the
Arizona-Nevada border, it is dammed again by Hoover Dam, located in Black Canyon; forming
the reservoir Lake Mead. There are four more dams on its route to the gulf. They are used for
recreation and irrigation. The New World Encyclopedia states that “The Colorado’s last drops
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evaporate in the Sonora Desert, miles before the river reaches the Gulf of California; 90% of the
water is used for irrigation purpose.”
Glen Canyon Dam had begun development in late 1956 and was completed on November
22, 1963 (Powell 79). Glen Canyon Dam is a hydroelectric arch dam made of concrete. The
Hoover Dam is concrete gravity-arch dam. Construction of this dam started in 1931 and was
completed in 1936. It was built for the purpose of supplying water and electricity to Arizona and
California. Also to gain control of the water that was flooding southern California and Mexico.
Since before these two dams where constructed; the Colorado River ran as a river that
was heavily laden with sediment and silt, the elements that created the Grand Canyon. The
Hoover Dam was the first to trap this sediment from making it to the west coast. Then Lake
Powell was created, it began to trap the sediment there at the intake of the lake. Creating a lake
of crystal blue water that is extremely colder than it was naturally, changing the habitat through
the Grand Canyon.
These measurements of sediment transportation were heavily monitored until the gates of
the diversion tunnels where close to fill up Lake Powell. Powell tells us,
In 1986, the bureau turned to sonar to measure the amount of silt on the floor of
Lake Powell. The study found that 868,000 acre-feet had accumulated, most of it
in a delta at the head of the lake, but some in a small wedge piled against the
upstream face of the dam. Over the lifetime of the lake, the average accumulation
calculates to 37,000 acre-feet per year (about 45,000,000 million tons). (203)
That would fill the lake in about seven-hundred years. With the recent drought, the water may
reduce but the sediment does not. At this same rate the lake will fill in 51 years (Powell 203).
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Since the Glen Canyon Dam is a hydro-electric dam, there are not drainage gates at the
foot of the dam to move the sediment through. The intakes for the eight turbines, which create
the power, are at an elevation of 3,470 feet above sea level. If the sediment reaches this level it
will damage the turbines and block these outlets. Leaving nowhere for the water to leave the
lake, “except for a trickle from the Paria River, between Lee’s Ferry and the mouth of the Little
Colorado, the mainstem Colorado River in the Grand Canyon would run dry” according to Dead
Pool. (Powell 204).
Rivers transport more water than sediment. The thought of sediment was over looked
when these dams where designed and built. Sediment inflow and outflow is a delicate balance.
Dam construction dramatically alters this balance. (Morris and Jiahua 2.3)
It is estimated the rate of storage loss in the coterminous 48 states in the United States at
0.22 percent per year (2020 millions of cubic meters) of annual storage loss. (Morris and Fan
2.13) If these numbers are true then Lake Powell will be filled in, in less time than it took the
Colorado River to make it. Lake Powell is in desperate need of sediment management. (Morris
and Jiahua 1.2)
There are five elements to sediment management:
1. Reduce sediment inflow
2. Route sediment
3. Sediment removal
4. Provide large storage volume
5. Sediment placement
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All of these elements should be looked at for Lake Powell. Reduction of the sediment
inflow could be done by capturing the sediment at the head of the reservoir. But what should be
done with this sediment once it is captured? It would cost millions of dollars to transport the
sediment, unless there is somewhere close to store it. It could be piped to bypass the reservoir. It
would still cost millions. Trying to redesign the dam; so that it has a gate at the foot of the dam,
would work very well. It would help move the sediment down into the Grand Canyon and restore
the ecological system of the canyon. This is a very dangerous and costly solution. It would be
better to dismantle the dam and let the river run its course. Dredging the lake as pointed out by
the Reservoir Sediment Handbook:
It is not feasible to recover the capacity of the larger reservoirs by
dredging because of high costs, which in the United States presently start at about
$2.50/meter cubed and increase as a function of longer pumping distances, deeper
digging depths, and increasing complexity of disposal. For example, at
$2.50/meter cubed it would cost 83 billion to restore Lake Powell fully
sedimented, assuming a suitable disposal site could be found for 33 km cubed of
sediment. (Morris and Jiahua 2.21,2.8)
Hydro suction dredging siphoning (Utah Division of Water Resources 63) is a very
resourceful way that sediment could be removed from the dam. It consists of pumping the
sediment over the top of the dam and down the other side to the river below the dam. This would
only reduce the sediment at the dam. If a combination of all of these methods where used it
would help in prolonging the life of Lake Powell. Also, it secures the resources that the dam
provides for the surrounding areas.
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Works Cited
“Colorado River.” NewWorldEncyclopedia.org. New World Encyclopedia, 7 June 2008.
17 Apr. 2011.
“Hoover Dam.” NewWorldEncyclopedia.org. New World Encyclopedia, 29 Aug. 2008.
17 Apr. 2011.
Morris, Gregory L. and Jiahua, Fan Reservoir Sedimentation Handbook. New York: McGrawHill Book Co., Web. 15 Apr. 2011.
Powell, James Lawrence. Dead Pool: Lake Powell, Global Warming, and The Future of Water
In The West. Los Angeles: U of California. P, 2008. Print.
Utah Division of Water Resources. Managing Sediment In Utah’s Reservoirs. Mar. 2010
Water.Utah.gov. Web. 15 Apr. 2011.