Headwork

Any device or structure at the head or the diversion point of the water way is said to be Headwork. There are two types of headwork are available, they are; diversion head-work and storage head work.

Storage Headwork

The dam is constructed across the river valley to form the storage reservoir is said to be storage headwork. The water is supplied to the canal from the reservoir through the canal head regulator. This serve as multipurpose functions like hydroelectric power generation, fishery, flood control, etc.

Diversion Headwork

This diversion headwork provides an obstruction across a river, so that the level of the water is raised and water is diverted to the channel at required level. The flow of water in the canal is controlled by the canal head regulator. This increased water level helps the flow of water by gravity and the increasing the commanded area and reducing the water fluctuation in the river.  As the velocity of the river decreases, the silt settles as the bed.

Functions of Headwork

The headwork serves the following purposes,

• This will increase the level of the water in the river.
• It is used to control the intake of water into the canal.
• It also controls the silt or deposit entry into the canal.
• It is also used to store water for small period of time.
• It is used to reduce the fluctuation level of water.

Site Selection for Storage Headwork

Remember these points before selecting the site for storage headwork,

• The hill area is preferred for the storage headwork, where the river valley is available to form a deep reservoir with minimum surface area.
• In the dame site good foundation should be available.
• In the reservoir area, there should be no cracks or preamble formations.
• The required capacity of reservoir is fulfilled, if the catchment area is wide.
• The river should not carry much sediment because this will form reservoir sedimentation.
• Road or railway communication to the site should be easy.

Site Selection for Diversion Headwork

• The river should be narrow and straight at the sight.
• The river bank should be well defined.
• When the weir or barrage is constructed, the valuable land should be submerged.
• The altitude of the site should be higher than the area to be irrigated.
• This also should be easily accessible to road or railways.
• For avoiding transmission loss, the site should not be far away from the commanded area of the project.

Questions:

• What is headwork?
• How to select site for the diversion headwork?