A dam is a large barrier built across a river or stream to confine and utilize the flow of the water. Often they are used in the generation of hydroelectricity. The water is directed across a series of turbines before being released out of the other side of the dam. A dam traps large amounts of water and create a reservoir or lake. This water can then be diverted for irrigation of crops or stored and used as drinking water. It can also be used to control flooding as it is able to be diverted elsewhere or released slowly.
The Construction of a Dam
The first step in constructing a dam is to choose an appropriate site for the dam. Dams are usually built where there is a natural narrowing of a river in a deep valley. This way the walls of the valley can be built between to create a dam. The next step is to divert the river away from this area so that the dam can be constructed. This is usually done using a tunnel or channel. A tunnel or channel is excavated by the building team diverting the water around the area where the new dam will be.
The river bed is then stripped of soil, gravel and sand that are not needed in the construction of the dam. The soft unsuitable material is taken away and the foundations of the dam are laid using concrete. Holes are then drilled, sometimes as deep as the dam will be high, and filled with concrete to provide strong foundations for the dam, this is called grouting. Once the foundation has been built the dam is then built on top. All dams have a water proof core that is often made of clay or other highly dense materials. Once the main dam has been constructed, other parts of the dam are worked on such as the spillway. The river is then diverted back into it original course and the dam tested for leakage and other issues.