Dam Building

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.2 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.3 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.4 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.5 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