Many people have already dammed a small stream using sticks
and mud by the time they become adults. Humans have used dams
since early civilization, because four-thousand years ago they
became aware that floods and droughts affected their well-being
and so they began to build dams to protect themselves from these
effects.1 The basic principles of dams still apply today as they
did before; a dam must prevent water from being passed. Since
then, people have been continuing to build and perfect these
structures, not knowing the full intensity of their side effects.
The hindering effects of dams on humans and their environment
heavily outweigh the beneficial ones. The paragraphs below will
prove that the construction and presence of dams always has and
will continue to leave devastating effects on the environment
around them.
Firstly, to understand the thesis people must know what dams
are. A dam is a barrier built across a water course to hold back
or control water flow. Dams are classified as either storage,
diversion or detention. As you could probably notice from it's
name, storage dams are created to collect or hold water for
periods of time when there is a surplus supply. The water is then
used when there is a lack of supply. For example many small dams
impound water in the spring, for use in the summer dry months.
Storage dams also supply a water supply, or an improved habitat
for fish and wildlife; they may store water for hydroelectricity
as well.
A diversion dam is a generation of a commonly constructed dam
which is built to provide sufficient water pressure for pushing
water into ditches, canals or other systems. These dams, which
are normally shorter than storage dams are used for irrigation
developments and for diversion the of water from a stream to a
reservoir. Diversion dams are mainly built to lessen the effects
of floods and to trap sediment.
Overflow dams are designed to carry water which flow over
thier crests, because of this they must be made of materials
which do not erode. Non-overflow dams are built not to be
overtopped, and they may include earth or rock in their body.
Often, two types of these dams are combined to form a composite
structure consisting of for example an overflow concrete gravity
dam, the water that overflows into dikes of earthfill
construction.
A dam's primary function is to trap water for irrigation.
Dams help to decrease the severity of droughts, increase
agricultural production, and create new lands for agricultural
use. Farmland, however, has it's price; river bottomlands
flooded, defacing the fertility of the soil. This agricultural
land may also result in a loss of natural artifacts. Recently in
Tasmania where has been pressure from the government to abandon
the Franklin project which would consume up to 530 sq miles of
land listed on the UN World Heritage register. In the land losses
whole communties must leave everything and start again elsewhere.
The James's Bay Hydroelectric project, hailed to be one of the
most ambitious North American undertaking of dams was another
example of the lands that may be lost. The 12.7 billion scheme
was to generate 3 160 megawatts of electricity a day, this power
output would be enough to serve a city of 700 000! One of the
largest problems with this dam, is that it would be built on a
region that meant a lot to 10 500 Cree and 7 000 Inuit. Lands
that their ancestors have hunted and lived on for more than 5 000
years will be flooded along with 90% of their trapping lines.6 If
this happened these people must resettle, find a new way of life
and face the destruction of a piece of their heritage if this
project is approved.
When a dam is being constructed, the river where it is
supposed to be built on must be drained. This kills much of the
life and disrupts the ecosystem and peaceful being of all the
aquatic and terrestrial animals around it. At fisheries there is
a large impact on the fish. The famous Columbia River saw it's
stock of salmon drop considerably after the dams were built,
although there were fish ladders built. The salmon were unable to
swim upstream when it was time for breeding as they usually did.7
But perhaps it is the plans for the Amazon Basin in Brazil
that shows us how large the side-effects can be. In the city
Surinam, in northern Brazil, Lake Brokopondo was created in 1864
swamping about 580 square miles of virgin rainforest. Foul
smelling gas called hydrogen sulfide was produced as the trees
decomposed. The turbine casings were attacked by the acidic water
and the decay of water allowed a chance for hyacinths to float on
the surface. This did not allow the light to shine through to the
water onto the plants which the fish feeded on. The plants were
unable to perform photosynthesis, and the fish died also because
there was a lack of food. In the lack of sun the waterweeds grew
and threaten to create diseases such as malaria, where the
whole lake's ecosystem would die out.8 Many little animals and
plants which were never discoved and may have had high economic
value were tobe lost forever.
There remains a problem with reservoirs which to date hasn't
been solved yet. A reservoir is a to store water, mainly for
hydroelectric power or irrigation. Nearly 10 000 caribou drowned
while crossing the inflated Caniapiscau River in September 1984,
because of these reserviors. The heavy rainfall created enough
water to overtop the structure and caused extra amounts of
spillages in the reservoir. The water flooded the river while the
caribou were literally submerged.
The Colarado River, known as the most litigated, controlled
and lesgislated river in the world. People who used to raft there
now say it is very insafe because of the fluctuating surges of
water meant to accomodate when the people use most energy. What
was fresh water is now being converted to salty water because of
these reservoirs. The water standing in the reservoir evaporates
when not used and the rest of the water becomes more salty.10
There is another theory that dams are causing earthquakes,
when these large structures are placed with the mass of the
unnatural weight of the lake near it, this disrupts the Earth's
surface and is a new precaution where before it was never heard
of. Many people say that dams protect people from natural
disasters, but there are some which it can intensify. For
instance if an Earthquake happens then, along with cracks in the
ground, buildings falling, there would also be a flood and large
pieces of the broken dam to cope with.
Dams are harming the environment that people live in. What was
being hailed as great accomplishments are now showing signs of
great consquence. The preservation of our environment is the key
to the preservation of people. We cannot exchange money for the
deterioration of our own animals, plants and land. The is the
environmental age and humans must respond by changing their
ways and looking at the long-term prospect instead of the short-
term. Until we as the users and protectors of the land can do
this, future of our great human civilization will continue to
look grim.
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