Rivers, Dams, and Levees
A global and local environmental issue
By Jack Van Holland
6/9/15
a. A river is “a body of water with current moving in one general direction”
(“River.”).
b. Rivers are vital parts of the environment and of human life.
i. Rivers are essential in moving sediments; “rivers drain nearly 75% of the
earth’s land surface” (Barrow).
ii. Rivers contain ecosystems that house numerous plants and animals
(Barrow).
iii. These plants and animals feed a massive amount of humans. For instance,
the Mekong River feeds an estimated 60 million people (Nijhuis).
iv. Rivers drain and collect fresh water, making them an important source of
water for humans (Barrow).
v. Rivers create fertile land and provide nutrients to agriculture (Barrow).
c. Alteration of river flow, such as dams and levees, cause serious implications on
both global and local levels.
II.
What are the major environmental problems facing the global community today?
a. River alteration causes major environmental problems in river ecosystems. Since
rivers are such an important resource to humans and the environment, any
environmental problems facing them become a large concern for the global
community as a whole.
b. Dams can be built for flood control, irrigation, hydropower, water storage, river
navigation, and recreation (Born). These dams have serious environmental
repercussions, however.
c. Blocking river flow with dams affects fish migrations. For instance, in the
Columbia River, fish populations have declined because of dams. In the mid-19th
century, wild salmon populations range from 10 million to 16 million. By the late
20th century, however, wild salmon populations declined to 375,000. This decline
in population was largely due to the dams built in the Columbia River. This has
caused a $6.5 billion loss of potential fishing. Dams have also caused 20% of
global freshwater fish to become endangered or extinct ("Damming Statistics.").
d. Dams also collect sediments, preventing them from contributing to fertile flood
plains or coastal wetlands ("Environmental Impacts of Dams."). In large
reservoirs caused by dams, for instance, 98% of sediments is trapped (“Damming
Statistics.").
e. Dams cause large amounts of flooding because they slow water flow, causing
reservoirs to form. This flooding caused 400,000 km 2 of land to be flooded and
caused 30 to 60 million people to be evicted ("Damming Statistics.").
f. Dams change the water chemistry of rivers, changing levels of dissolved oxygen,
nitrate, turbidity, and temperature. These changes affect the aquatic plants and
animals of the ecosystem ("Environmental Impacts of Dams.").
g. A global issue is persistent, transnational, interconnected, and significant. River
alteration is a persistent issue because dams, levees, and other changes to river
flows have been occurring since ancient Egypt ("When Did People Start Building
Dams."). This is transnational because it is occurring across the globe, not only in
one country. This is significant because rivers are so important to people and the
environment and changes to the river can have serious affects for people who rely
on the rivers. This issue is interconnected because it is involved in many other
issues. For instance, dams are built to provide electricity without carbon emission,
helping reduce effects on climate change.
h. Overall, changing the flow of rivers by implementing dams or levees affects the
ecosystem, causing a major problem for the global community.
III.
How do environmental issues impact our local community?
a. The Snake River levee system was constructed from 1957 to 1964 in order to
provide protection from severe flood protection (Anthony). This levee system,
however, had severe environmental effects on the Snake River.
b. The levee constricted and altered the flow of the river.
i. Naturally, the river had a “complex braided structure” that was
transformed into a “single or double main channel” (Anthony).
ii. This channel is 1000-1600 feet in width compared to the natural 10004000 feet river width. The Snake River floodplain has been reduced from
25,000 acres to 2500 acres, reducing wetland areas (Anthony).
iii. This constriction of the river caused an increased water flow rate
(Anthony).
iv. This increased water flow rate caused increased erosion of the river bed,
lowering the bed’s elevation (Anthony).
v. This eroded material may have been deposited downstream in slower
moving sections of the river (Anthony).
c. Due to these changes in the river, numerous species of plants and animals were
affected (Anthony).
i. One cause of this is changing of habitat. For instance, large portions of
the Snake River floodplain were dewatered, the current of the Snake River
was increased, and the width of the Snake River was decreased. Due to
these changes and many others, an estimated 1/3 to ½ of habitat was lost
(Anthony).
ii. The levees have caused decreased population in young cottonwood
seedlings and saplings. This has been largely due to less water
disturbance on the ground from flooding, causing older cottonwood trees
to have increased lifespans. These older trees blocks sunlight for reaching
the ground, causing smaller cottonwoods to die. To have a healthy
population of cottonwoods, however, young cottonwood trees must be
allowed to replace the older ones (Anthony).
iii. Since some areas beside the river in which the water formerly flowed have
been dried, different species of plants, such as spruce, are now growing
there (Anthony).
iv. Unvegetated shore along the river has been decreased. The remaining
unvegetated shore is located closer to mainland, decreasing the value for
bird nesting (Anthony).
v. The levee has a huge impact on cutthroat trout populations. The increased
velocity of the river cause is challenges for fishes’ feeding. The
channelization of the Snake River eliminated spawning areas on the main
channel. Trout usually spawn in tributaries of the river. Before the levee,
the river’s flooding would replace gravel necessary for trout spawning.
Overall, the levee has increase the difficulty of trout spawning and in turn
decreased trout populations. (Anthony).
vi. Jackson Hole is a popular tourist destination greatly due to the natural
scenery and wildlife. Problems with the environment could impact the
scenery and wildlife and decrease tourism in Jackson Hole. Since tourism
is large part of the economy in Jackson Hole, a decrease in it would affect
people who live there greatly.
d. Overall, our local community has been affected by the levee along the Snake
River. The levee has changed the flow of the river, causing changes and problems
in the environment. These changes threaten the ecosystem of the Snake River, the
ecosystem of Jackson Hole, and Jackson Hole’s economy.
Works Cited
Anthony, Paul. "The Snake River Levee System Report." Jhalliance.org. Jackson Hole
Conservation Alliance, 1 Sept. 1998. Web. 2 June 2015.
<http://www.jhalliance.org/Library/Reports/levee.pdf>.
Barrow, Mandy. "Why Are Rivers Important?" Primaryhomeworkhelp.co.uk. Mandy Barrow.
Web. 1 June 2015. <http://www.primaryhomeworkhelp.co.uk/rivers/importance.html>.
Born, Sara. "Lesson: Why Do We Build Dams?" Teachengineering.org. Regents of the
University of Colorado. Web. 1 June 2015.
<https://www.teachengineering.org/view_lesson.php?url=collection/cub_/lessons/cub_da
ms/cub_dams_lesson01.xml>.
"Damming Statistics." Internationalrivers.org. International Rivers, 22 Oct. 2007. Web. 1 June
2015. <http://www.internationalrivers.org/es/damming-statistics>.
"Environmental Impacts of Dams." Internationalrivers.org. International Rivers. Web. 1 June
2015. <http://www.internationalrivers.org/environmental-impacts-of-dams>.
Nijhuis, Michelle. "Harnessing the Mekong or Killing It?" Ngm.nationalgeographic.com.
National Geographic Society, 1 May 2015. Web. 1 June 2015.
<http://ngm.nationalgeographic.com/2015/05/mekong-dams/nijhuis-text>.
"River." Fcps.edu. Fairfax County Public Schools. Web. 1 June 2015.
<http://www.fcps.edu/islandcreekes/ecology/river.htm>.
"When Did People Start Building Dams." Damsafety.org. Association of State Dam Safety
Officials. Web. 1 June 2015. <http://www.damsafety.org/community/kids/?p=c8a91672d611-44b4-b744-5a02c6c32eb4>.