Why dam is important

By using concrete, the weight of the dam is actually able to resist the horizontal thrust of water pushing against it. This is why it is called a gravity dam.

An earth dam is made of earth or soil built up by compacting successive layers of earth, using the most impervious materials to form a core and placing more permeable substances on the upstream and downstream sides. A facing of crushed stone prevents erosion by wind or rain, and an ample spillway, usually of concrete, protects against catastrophic washout. A rockfill dam is built of rock fragments and boulders of large size. An impervious membrane is placed on the rockfill on the upstream side to reduce the seepage through the dam.

The membrane is usually made of cement concrete or asphaltic concrete. Buttress dams are of three types: i Deck type, ii Multiple-arch type, and iii Massive-head type. A deck type buttress dam consists of a sloping deck supported by buttresses. Buttresses are triangular concrete walls which transmit the water pressure from the deck slab to the foundation. Buttresses are compression members.

A steel dam consists of a steel framework, with a steel skin plate on its upstream face. Steel dams are generally of two types: i Direct-strutted steel dams, and ii Cantilever type steel dams.

In a direct strutted steel dam, the water pressure is transmitted directly to the foundation through inclined struts. In a cantilever type steel dam, there is a bend supporting the upper part of the deck, which is formed into a cantilever truss.

Main load-carrying structural elements of timber dam are made of wood, primarily coniferous varieties such as pine and fir. Timber dams are made for small heads m or, rarely, m and usually have sluices; according to the design of the apron they are divided into pile, crib, pile-crib, and buttressed dams.

A subsidiary dam of any type constructed across a saddle or low point on the perimeter of a reservoir. This is similar to a levee , which is a wall or embankment built along a river or stream to protect adjacent land from flooding. A weir also sometimes called an overflow dam is a type of small overflow dam that is often used within a river channel to create an impoundment lake for water abstraction purposes and which can also be used for flow measurement or retardation.

This is used to control the soil erosion. This is a small dam and it reduce the flow velocity to control soil erosion. A dry dam, also known as a flood retarding structure, is a dam designed to control flooding.

It normally holds back no water and allows the channel to flow freely, except during periods of intense flow that would otherwise cause flooding downstream. Underground dams are used to trap groundwater and store all or most of it below the surface for extended use in a localized area.

In some cases they are also built to prevent saltwater from intruding into a freshwater aquifer. Underground dams are typically constructed in areas where water resources are minimal and need to be efficiently stored. The Romans built an elaborate system of low dams for water supply. The most famous was the Cornalbo earth dam in southern Spain which had a height of 24 meters 78 feet and a length of meters feet. The building of the Marib dam in Yemen began around BC and took years to complete.

It consisted of an earth embankment 4 meters in height and stone sluices to regulate discharges for irrigation and domestic use. In , the existing dam was raised to 38 meters that created a reservoir of Mm3.

The Sayamaike dam, one of the oldest dams in Japan, was built in the early 7th century and after several modifications and a heightening is still in use today. Students apply what they learn about the salmon life cycle as they think of devices and modifications t Students learn about the importance of dams by watching a video that presents historical and current information on dams, as well as descriptions of global water resources and the hydrologic cycle.

Students also learn about different types of dams, all designed to resist the forces on dams. Students learn that dams do not last forever. Similar to other human-made structures, such as roads and bridges, dams require regular maintenance and have a finite lifespan. Where does your water come from? Mountains, rivers, reservoirs? What is a reservoir?

A reservoir is a human-made lake created by building a dam. Why do we need dams? When you turn on a faucet at home, where does that water come from? Why is there always water coming out? There is always a supply of water because we hold water in reservoirs. To do this, we must build dams. Why else do we build dams? Take suggestions; write answers on the board. Dams are important because they provide water for domestic, industry and irrigation purposes.

Dams often also provide hydroelectric power production and river navigation. Domestic use includes everyday activities such as water for drinking, cooking, bathing, washing, and lawn and garden watering. Dams and their reservoirs provide recreation areas for fishing and boating.

They help people by reducing or preventing floods. During times of excess water flow, dams store water in the reservoir; then they release water during times of low flow, when natural flows are inadequate to meet water demand. When engineers design and maintain dams, they consider all these purposes. Bagnell Dam on the Osage River in Missouri.

All rights reserved. For the next several lessons, you are going to be civil engineers working for the company Splash Engineering. Your main client is the government also known as a "municipality" of Thirsty County. The government of Thirsty County has been receiving complaints from its residents over the last decade. The main problems include:. The Thirsty County government has hired the Splash Engineering firm your class to study the needs of the community and develop a solution that addresses those needs.

Dams are usually constructed to store water in a reservoir, which is then used for a variety of applications such as irrigation and municipal water supplies. Reservoir water can also be directed to flow through hydraulic turbines, producing electric power for use in homes and industries. Hydroelectric power is considered a renewable source of energy because the reservoir water that is used to generate electricity is continuously replenished.

A dam using locks and canals, such as the series of locks on the Panama Canal, enables navigation through a human-made water route that must overcome elevation differences. The disadvantages of dams include the resulting flooding of large areas of land destroying flora and fauna , altering the physical characteristics of the river below the dam also affecting flora and fauna , impeding fish migration, and killing large numbers of fish that pass through hydroelectric turbines.

In recent years, engineers and scientists have begun to manage reservoirs and their releases to be less harmful to aquatic and terrestrial wildlife and plants, as well as humans residing below the dam—a method of water resource management called adaptive management.

Dams can be useful for a variety of reasons. What are some purposes for which we create dams? Answers: To supply water for irrigation, municipal water, flood control, hydroelectric power generation, river navigation. What might be negative effects from a dam? Answers: Upstream flooding that destroys animals, plants, ecosystems and private property; downstream alteration of terrain, ecosystems, plants and wildlife; impeding fish migration, killing fish that pass through turbines, etc.