The Colorado River and Dam

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The Colorado River and Dam

• Case Study

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Back ground information

• With a drainage basin covering 630000 km, the
  Colorado is the third largest river in North
  America, after the Mississippi and the Columbia.
  Its source is the snowfields of the Rocky
  Mountains in Colorado and Wyoming Its mouth is
  the Gulf of Columbia in Mexico, 2300km to the
  southwest. (see picture 1 on picture page)
• Apart from the Rocky Mountains, most of the
  Colorado drainage basin is desert. The climate at
  Moab on the Colorado Plateau is typical.
• Mean annual rainfall is low and
  evaportransiration in summer, when temperatures
  routinely rise above 40c, is high.
• On the Colorado Plateau, the combination of
  erosion by the Colorado River, tectonic uplift
  and desert climate have produced some of the
  worlds most spectacular landforms. They include
  the Grand canyons horse shoe bend ( picture 3),
  The grand canyon (picture 2) and the entrenched
  meanders or goosenecks on the San Juan River
  (picture 4) .

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Managing water resources in the Colorado basin

• The Colorado River flows across the arid Colorado
  Plateau and Great Basin. There water is scarce
  significant amounts are only available from the
  Colorado River and its tributaries. This explains
  why the Colorado is the most dammed river in the
  USA.
• In its lower course in Nevada, Arizona and
  California, the Colorado is little more than a
  series of reservoir is created by the Hoover,
  Davis, Parker and Imperial Dams.
• The Colorado River is used between 8 states. It
  is all tied up in a legal agreement (CRC- The
  1992 Colorado River Compact) Ninety of the
  water is used for irrigation and agriculture. The
  rest is used by authorities from L.A, San
  Diageo, Phoenix, Denver, Salt lake city and Las
  Vegas.
• Since the states have all had surges in their
  population and economic growth, they have all
  started to exceed their legal share. This is
  mainly in California. Now, Arizona, Nirvana and
  Colorado have put a squeeze California and called
  upon its sustainability of the current waters
  supplies.
• The four dams I mentioned earlier Hoover, Davis,
  Parker, Imperial Dams control the water resources
  in the lower basin. Nevada already uses its full
  allocation of water under the CRC and is urgently
  searching for new ground water supplies in the
  Mojave Desert north of the city.
• 50 of southern California's water comes from the
  Colorado River. Series of aqueducts of the Hoover
  Dam provide water for irrigated agriculture in
  the imperial Valley and the Paulo Verde and Yuma
  irrigation areas. Also water is supplied to the
  metropolitan areas of L.A and San Diego.
• Like Nevada's demand for more water, Arizonans
  need for water has increased immensely over the
  last 30 years.
• What is left of the Colorado's flow when it
  finally reaches Mexico is diverted mainly to
  irrigation. There have been major issues
  concerning the quality of this water. Much of it
  is run off from irrigated land in southern
  California, and has high levels of salinity that
  make it unfit for agriculture.

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Glen Canyon dam

• The Glen Canyon was the last major dam built on
  the Colorado. Completed in 1963, it was sited at
  the narrowest point in the canyon close to the
  Utah-Arizona border. Its location was so remote
  that a small town, page, was built tom
  accommodate the workers.
• The primary purpose of the glen canyon dam was to
  improve water management in the lower basin.
• The dam created a huge reservoir-Lake Powell
  over 300km long and with a surface area of nearly
  1650km. This is very useful lake in times of
  flooding and securing water supplies for drought
  periods.
• The other purposes of the dam include
  Generating power (1300MW OF HYDRO) This power
  goes to the 7500 inhabitants of Page and to the
  near by power station. Also the lake offers a
  wide variety of water based sports and leisure
  activities such as Sailing, rowing, fishing,
  walking.
• What ever the dam has achieved has come at the
  cost of the environment. The impact is greatest
  down stream of the dam. Creating the dam has
  degraded the rivers ecosystem between Glen Canyon
  and Lake Mead.
• The lake has changed The Colorado River. Before
  construction its channels flooded every spring
  and the water was warm and muddy. Because the
  Dam acts as a sediment trap, the water leaving
  lake Powell is clear and because of how deep it
  is the water temp is now a constant 8c.
• Effects of these changes are Deprived of
  sediment and flood waters, sand banks that
  previously formed within the river channel have
  been eroded. The loss of Important habitats for
  fish, amphibians and birds have been lost. Also
  the fish migration was unable to occur with the
  dam. Because of all this 3 fish species have been
  extinct and 5 more are now endangered. With out
  the floods to clear out bank side vegetation,
  alien plant species like Tamarisk have been able
  to colonize the canyons, which now dominate large
  tracts of the river bank. These create new
  habitats for animals.
• Up stream the effects have been just damaging
  Beautiful scenery has been flooded dew to lake
  Powell.
• There have been attempts to drain lake Powell by
  conservationist groups. They want to restore
  Colorado to it wild state, rehabilitate its
  unique ecosystems and reclaim hundreds of square
  km of desert canyons. People have obviously been
  fighting for the lake to stay where it is. No
  more then the people of Page whose lively hood
  depends on its existence. Especially the tourism
  it brings and the money that comes with it.
• Losing the dam would also mean losing all the
  power that is generated from its dam. And the
  counties supplied would be effected in terrible
  ways, and it would be a monster of a task finding
  other sources that could satisfy.