Grade 10 Geography
Units 12, 13, 14
Essay - Effects of 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.

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 ...