Civilsolution.

What is Dam

Definition of Dam is as an obstruction constructed across a stream or river. At the back of this barrier water is collected forming a pool. The side on which water is collected is called upstream side and the other side of the barrier is called downstream side. The pool of water which is formed upstream is called a Reservoir.

Uses of Dams and Reservoirs

Following are the uses of Dams

• The water collected in the lake can be used for recreation, as a reservoir of drinking water or it can be supplied to the surrounding farm land through canals for irrigation.
• The energy of this collected water can be used to turn a mill to grind wheat or to turn the blades of a turbine to generate electrical power.
• In times of floods, uses of dams can serve as protections for the towns and cities downstream of the river.
• Apart from these advantages dams are very significant in times of war. As they help in planning war strategies and in controlling the advancement of enemy forces.

Dams can be classified in various ways depending upon the purpose of classification

1. Earth Dams
2. Rock fill Dams
3. Solid masonry gravity Dams
4. Hallow masonry gravity Dams
5. Steel Dams
6. Timber dams
7. Arch dams

The first three types of Dam are ancient in origin while the last four have come in general use only in the last century or so.

1. Storage Dams
2. Detention Dams
3. Diversion Dams

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Types of Dams, Earth Dam, Rock Fill Dam, Arch and Storage Dam

                                                                                                                           Types of Dams

Following are the types of Dams

Earth Dams are constructed of soil pounded and compacted into solid mass. These are constructed in areas where the foundation is not strong to bear the weight of a concrete dam and where earth is easily available.

Rock fill Dams are formed of loose rocks and boulders piled in the river bed. A slab of reinforced concrete is often laid across the upstream face of a rock fill dam to make it water tight.

Solid Masonry Gravity Dams are big and expensive to be built but are more durable and solid than earth and rock dam. They can be constructed on any dam site, where there is a natural foundation strong enough to bear the weight of the dam.

Hollow Masonry Gravity Dams are designed on the same lines on which the solid masonry gravity dams are designed but they contain about 35 to 40 % less concrete or masonry. Generally the weight of water is carried by a deck of R.C.C.

Steel Dams are used as temporary coffer dams needed for the construction of permanent dams. Steel coffer dams are usually reinforced with timber or earth fills.

Timber Dams have short life usually not more than 30 to 40 years and must have regular maintenance during that time. However they are valuable in agricultural areas for meeting low level needs.

Arch Dams ae very complex and complicated types of Dams. They make use of the horizontal arch action in place of weight to hold back water. They are best suited for sites where the dam is required to be very high and narrow.

Storage Dams are constructed in order to store water during the periods of surplus water supply. The stored water can be used in different seasons and for different uses. These dams may be further classified depending upon the specific use of the water, such as navigation, recreation, water supply and electricity etc.

Diversion Dams are small dams used to raise the river water level, in order to feed an off-taking canal. A diversion dam is generally called a weir or barrage.

Detention Dams detain flood waters temporarily so as to retard flood run-off and thus minimize the effects of floods. Detention dams are sometimes built to trap sediment. They are often called debris dams.

Overflow Dams are designed to pass the surplus water over their crest. They are often called spillways. They are made of materials that do not erode with such discharges.

Non-Overflow Dams are those which are not designed to be overtopped. This type of design gives wider choice of materials including earth-fill and rock-fill dams.

Rigid Dams -Rigid dams are constructed of earth and rock-fill.

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