Dams are obstructions constructed across the water bodies to control the water flow and water levels. Each components of dams play specific roles in managing their prime responsibility of managing water. This article is about the components of dam and their functions.

The part of the dams where the water is collected is known as the upstream side. On the upstream side, the water level is high. The portion of the dams with a low water level is known as the downstream.

Also read : Dams- Importance, Site selection, Advantages

Also read : Types of dams- Three classification criteria explained

Components of Dams

Components of dams play an important roll in their functions and essential parts of the dams are broadly classified as follows.

• Heel
• Crest
• Parapet wall
• Toe
• Abutment
• Conduit
• Cutoff
• Galleries
• Diversion tunnel
• Spillways
• Sluice way
• Free board

Heel 

The part of the dams meeting with the groundwater or upstream side is called the heel. (Ref fig.)

Toe

The portion of the dams meeting with the groundwater or downstream side is called the Toe.(Ref fig)

Crest/Roadway of Dams

The section of the dams used as a roadway or walkway is the crest. It is the upper area of the dam.

Also read : Components of a bridge – Types and functions

Also read : Components of a road pavement structure – Parts of a road

Parapet wall

The parapet wall is seen below the crest near the roadway. This assists in the dam investigation and safety barriers.

Abutment

Abutments support the lateral pressure. These are sides of the valley. These are concrete or masonry structures. 

Galleries

These are hollow openings passing through the dam as shown in fig. The main purpose of providing drainage gallery is to collect seepage water from the foundation and body of the dam, and drain it out. The seepage water received by foundation galleries is drained away under gravity. The galleries are broadly divided into …

• Grouting gallery
• Inspection gallery
• Drainage gallery
• Valve gallery
• Transformer gallery

Diversion tunnel

The purpose of the diversion canal is to redirect the water. Diversion tunnels are constructed during the construction stage of dams.

A diversion tunnel may also be constructed to divert floodwaters to divert water from mountainous regions to low lying areas experiencing a water shortage supply.

Conduit

These are closed pipe structures. Conduits act as a passage for the water supply. Bottom discharge conduits are pipes that cross the body of the dam from the upstream to the downstream sides enabling water flow.

Cut off 

Cut off is an impervious barrier constructed beneath the earthen dams .The main function is to reduce the loss of stored water in the reservoir by preventing seepage.

Spillway

The role of the spillway is conveying excess water and preventing damages. The water passes from upstream to downstream. Spillway helps in the emergency discharge of water. 

They are two varieties

• Controlled spillway 
• Uncontrolled spillway

In a controlled spillway the flood flow is regulated by the gate. 

Also Read : Spillway types and features – A comprehensive guide

Sluice way

The role of the sluiceway is to remove the silt accumulated. 

Freeboard

The interval between the dam heads to the maximum water level on the upstream side.

Examples of some major dams

Bhakra Dam ( Gravity dam )

The Bhakra Dam is an Indian gravity dam built across the river Sutlej in Himachal Pradesh. This dam is constructed in 1963. The height of the dam is 226 meters. The length of the dam is 518 meters.
Gobind Sagar is a reservoir of this dam. The Bhakra Dam composed of alternating layers of light red clays and sandstone.
This dam has four spillways. It helps in irrigation, hydroelectric power generation and recreation. The major source of irrigation water supply in Haryana, Punjab and Rajasthan is this dam.

Idukki dam ( Arch dam )

Idukki dam is an arch dam constructed across the Periyar river in Kerala. It is 554 feet high. One of the biggest arch dam in Asia. The dam provides hydroelectricity, irrigation and tourist destination. It is built between Kuravan and Kurathi hills.

Nagarjuna Sagar Dam (Masonry Dam)

Nagarjuna Sagar Dam is a stone masonry dam completed in 1967. The dam is the symbol of modern architecture. The purpose of this project was to generate hydroelectricity. It has a 26 crest gate.

The Hirakud Dam (Earthern dam)

The Hirakud dam is located in Orissa state over the river Mahanadi near Sambalpur. The length of the dam is 4800 meters and 59 meters high. It is the oldest multipurpose dam completed in 1957.
The Hirakud Dam is the 4800-meter length and 59 meters high. The gross storage capacity of the dam is 1841 million cum.

KARIBA DAM (Double curvature arch dam)

Kariba Dam is a double curvature arch dam constructed in 1960. It has been built over the Zambezi river. The crest length is 620m and 128m high. The dam provides an example of improving the quality of rocks.