Components of a dam

The Components of a dam are,

1. Dam
2. Reservoir
3. Upstream side
4. Downstream side
5. Catchment area
6. Spillway
7. Crest
8. Sluice or Gate
9. Heel
10. Toe
11. Full reservoir level (F.R.L.)
12. Gross storage capacity of the reservoir
13. Live storage
14. Dead storage
15. Mean sea level (M.S.L.)
16. Maximum water level (M.W.L.) or High flood level (H.F.L)
17. Free board
18. Drainage gallery
19. Anacut
20. Stability of dam structure

Dam

A dam is a heavy hydraulic structure, constructed across a river. It stores water on one side up to a certain level. A dam is an impervious barrier (obstruction), build across a natural stream of water so that a Reservoir is formed.

Reservoir

The total impounded water collected on the upstream side is called Reservoir

Upstream side

The side of the dam on which water gets collected is called the upstream side.

Downstream side

It is the stretch of the stream below or down the dam.

Catchment Area

The catchment area is the rainfall area on the upstream side of the dam. It is feeding water to the reservoir of the dam. The catchment area decides the capacity of the reservoir as well as the height of the dam.

Spillway

The spillway is the waterway for the overflow of a dam. It acts as a safety valve for the dam. Its function is to let out the excess water from the dam to the downstream side otherwise, the excess water in the dam may cause a breach of the dam due to over-storage.

Crest

The crest is the top surface of the dam. It may be used as a roadway.

Sluice or Gate

It is the component of a reservoir with regulating arrangements to control the quantity of water. Through the sluice, water is let out from the upstream side of the dam.

Heel

The heel of the dam is the upstream end of the base of the dam.

Toe

The Toe of the da is the downstream end of the base of the dam.

Full reservoir level (F.R.L.)

The full reservoir level is the level up to which water can be stored in the reservoir of the dam.

Gross storage capacity of the reservoir

It is the total quantity of water stored in the reservoir up to full reservoir level.

Live storage

Live storage is the quantity of water stored in the dam from the level of the lowest set of sluices to the full reservoir level

Dead storage

Dead storage is the quantity of water stored below the level of the lowest set of sluices in the dam. This water cannot be released out and used for irrigation, etc

Mean sea level (M.S.L.)

Mean sea level means the height of the dam above the sea level

Maximum water level (M.W.L.) or High flood level (H.F.L.)

During floods, water may be allowed to rise above the full reservoir level to a certain maximum level, called maximum water level (M.W.L.) or High flood level (H.F.L.). The top surface of the dam is always constructed above the maximum water level of the reservoir.

Free board

The free board is the difference in height between the top surface of the dm (crest) and the maximum water level of the reservoir.

Drainage gallery

It is a passage left inside the dam, provided along the length of the dam above the river bed. Its purposes are:

• To drain the water seeping through the foundation and upstream masonry
• To serve as a longitudinal inspection chamber

Anacut

Anacut is the area to be irrigated by a dam

Stability of the dam structure

The load of the heavy structure of the dam acts vertically downwards on the foundation. Due to the storing of water in the reservoir on the upstream side, a lateral thrust of high magnitude acts on the dam. This thrust tends to push the dam to the downstream side.

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