A dam as a water retaining system:
what is it, how does it work
A dam is one of the most important structures that humans build. They allow us to control the flow of water not to mention to have electricity and drinking water. People have building dams for centuries making them some of the oldest construction projects on the planet. Even today they remain an important part of our infrastructure.
A dam is a structure that is designed to impound water. The main reason that they are built is to provide a reservoir of water for use in generating hydroelectricity. In some cases dams are also used to hold water for storage, usually so that it can be used for drinking water. It is important to understand the difference between a dam and a dike. A dike is designed to control the flow of water. A dam on the other hand is intended to create a reservoir of water.
The actual construction of a dam can be quite complicated, the pressure of the water against the dam is enormous and they have to be built to withstand them. The most common design, at least for large dams is an arch dam. These are designed for the same reason that arches are used to hold up bridges or roofs on buildings, the arch is a very strong structure. There are several other designs that that can be used as well but they are usually limited to use on the smaller dams that are not subject to as much water pressure.
Dams these days are mostly built out of concrete. Again there are exceptions to this but it is usually limited to smaller dams. Early dams were built out of wood but that is fairly rare these days. It is however still fairly common to build dams using rocks or dirt to hold back the water. This is the simplest way to build a dam but the size that can be built is fairly limited. In recent years there has been some work done on building dams out of steel but these tend to be limited to dams that are designed to be opened and closed.
Although it may not look like it a dam is fairly complicated piece of machinery. This is mainly because of the need to control the water level behind the dam. It is necessary to have spillways that allow water in the correct amount to get past the dam. This is made more difficult since the level of the river often varies which means it is necessary to control how much water goes through the spillway. If the dam is being used for hydroelectricity it will also be necessary to send water running past the turbines. Again the amount needs to be properly controlled to ensure that the turbines work properly.