COMPONENT PARTS OF A WEIR
Introduction
Generally, inundation canals derive their supply during the rainy season only when the water level in
the river rises. Thus, the canal system comes into operation when the water is very urgent. Hence, it
is essential to construct a permanent canal system in culturable tract in order to supply the water
during low flows according to requirements. It is now needless to mention that the river discharge is
never constant and regular. So it is necessary to construct some structures at the head of canal to
take care of irregularities in river flow condition since these works are constructed at the head of the
canal system they are termed as “Canal Head Works”
CLASSIFICATION OF HEAD WORKS
The works which are constructed at the head of the canal in order to divert the river water towards
the canal so as to ensure a regulated continuous supply of water are known as “Head Works”. Since
these works are constructed at the head of the canal system they are termed as “Canal Head
Works”.
Head works may be divided into classes:
1. Storage head work
2. Diversion head work
Storage Head Work:
A storage head work comprises the construction of a dam across the river. It stores water during the
period of floods in the river and releases it as and when required to the down stream side.
Diversion Head Work:
A diversion head work is to divert the required quantity of water into the canal from the river.
SELECTION OF SITE FOR HEAD WORKS
1. The construction materials should be available locally in large quantities.
2. The section of the river should be narrow and hence it reduces cost of head works and river
training works.
3. The site should be close to the culturable area and hence reducing the cost of canal system.
4. Number of cross drainages works to be constructed should be minimum.
5. The river reach should have central flow to prevent the scouring.
6. The canal should cover maximum command.
7. At the site good foundation should be available at moderate depth.
8. The cost of connecting work at the side by rail and roadways should be minimum.
FUNCTION OF DIVERSION HEAD WORKS
A diversion head work serves the following purposes.
1. It raises the water level in the river so that commanded area can be increased.
2. It regulates the intake of water into the canal.
3. It controls the entry of silt inti the canal.
Introduction
Generally, inundation canals derive their supply during the rainy season only when the water level in
the river rises. Thus, the canal system comes into operation when the water is very urgent. Hence, it
is essential to construct a permanent canal system in culturable tract in order to supply the water
during low flows according to requirements. It is now needless to mention that the river discharge is
never constant and regular. So it is necessary to construct some structures at the head of canal to
take care of irregularities in river flow condition since these works are constructed at the head of the
canal system they are termed as “Canal Head Works”
CLASSIFICATION OF HEAD WORKS
The works which are constructed at the head of the canal in order to divert the river water towards
the canal so as to ensure a regulated continuous supply of water are known as “Head Works”. Since
these works are constructed at the head of the canal system they are termed as “Canal Head
Works”.
Head works may be divided into classes:
1. Storage head work
2. Diversion head work
Storage Head Work:
A storage head work comprises the construction of a dam across the river. It stores water during the
period of floods in the river and releases it as and when required to the down stream side.
Diversion Head Work:
A diversion head work is to divert the required quantity of water into the canal from the river.
SELECTION OF SITE FOR HEAD WORKS
1. The construction materials should be available locally in large quantities.
2. The section of the river should be narrow and hence it reduces cost of head works and river
training works.
3. The site should be close to the culturable area and hence reducing the cost of canal system.
4. Number of cross drainages works to be constructed should be minimum.
5. The river reach should have central flow to prevent the scouring.
6. The canal should cover maximum command.
7. At the site good foundation should be available at moderate depth.
8. The cost of connecting work at the side by rail and roadways should be minimum.
FUNCTION OF DIVERSION HEAD WORKS
A diversion head work serves the following purposes.
1. It raises the water level in the river so that commanded area can be increased.
2. It regulates the intake of water into the canal.
3. It controls the entry of silt inti the canal.
