Water is a natural resource that is used by all living things to maintain life. The flow of water varies from one water source to another. To get control over fast flowing waters, man has built dams. A dam or a reservoir is considered as man’s triumph over nature.

Fact 1 What Is A Dam?
A dam is a massive barrier built across a river or stream to confine the water and utilize the flow of water for human purposes. When water is confined in this method lake and reservoirs are created. Innumerable dams have been built all over the world to use the natural resource in various ways and with the development of civilization, the number of dams increased. The first known was built across the River Nile in 2900 B.C. to protect the city of Memphis from flooding. Thereafter, other dams were built during the Roman Empire after which there was a halt in the construction of dams until the 1800s. It has been fund that dams are not only built by man, but they are present in nature also. Beavers build dams to keep the water deep enough to cover the openings to their homes for protection against predators.

Fact 2 Why Dams Are Built
Scientists found that if the flow of water can be restricted and then allowed to flow through water gates at great speed, it can be used to generate hydroelectricity. There are other reasons for building dams across rivers especially the fast flowing rivers and also streams.
Some dams are built to divert the natural flow of the river water and use it for irrigation purposes.
Dams are also constructed to control floods. They are called detention dams and are constructed to either stop or slow down the amount of water in a river.

Fact 3 How Dams Benefit Humans
However the two main functions of dams are to store water to compensate for fluctuations in river flow or in demand for water and energy. The storage system allows the dams to generate electricity which is nearly a fifth of the world’s electricity. Dams supply water through cut out channels to agricultural lands, industries and also to homes. Another important advantage of constructing dams is assisting river navigation by providing regular flows and drowning rapids. Dams are sources of leisure activities like boating and reservoir fisheries.

Fact 4 Uniqueness Of Dams
Every river has its own specialty and uniqueness and so also the watersheds. So dams built across rivers are different from one another. There are three types of dams namely the arch, gravity and embankment dam. The type of dam design is selected according to the site of the dam, geology and topography of the area. Most of the large dams are the embankment dams and they are the cheapest to build. They are made of earth and rocks and are generally built across broad valleys near sites where the raw materials required for construction are available in large quantities. These dams are the largest structures erected by humans. Gravity dams are actually very thick and have straight walls and the arch dam looks like a normal architectural arch pushed onto its back while the curved top faces upstream and feet braced against the sides of the canyon.

Fact 5 Effects Of Dams On Humans
Large dams have forced millions of people to leave their lands and homes. The tribal, peasants and all those who live near the rivers and farmlands are worst hit and psychologically devastated. Many people have lost access to clean water and food sources and also diseases that large irrigation projects and dams bring in to the tropical areas. Earthquakes can also be induced by dams.