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


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.