Diversion headworks are structures constructed at the head of a canal to divert river water into the canal. They include weirs or barrages that raise the water level, as well as other components like canal head regulators, divide walls, fish ladders, and scouring sluices. The objectives of diversion headworks are to raise water levels, form water storage, control silt entry, and regulate water levels during different seasons. Key considerations for siting diversion headworks include river characteristics, elevation, foundation stability, and access for construction materials.

1. - Mr. Hole G.R.
Lecturer-Civil Department,
JSP,HADAPSAR

2.  The works which are constructed at the head of the canal
in order to divert the river water toward the canal, so as
to ensure a regulated continuous supply mostly silt free
water with certain minimum head into the canal, are
known as diversion headworks.

3.  Storage Headwork :
A storage Headwork is structure( Dam) which is constructed
across river to store water during excess inflow and used to
supply during less inflow and high Demand.
 Diversion Headwork:
It is structure which constructed across river (Weir) to raise the
water level in river so that it can diverted in to canal system.

4. The Following are the objective of Diversion Head works
 To Raise the water level at the head of canal.
 To form a storage by construction of dykes on both
side of banks of the river so that water is available
throughout the year.
 To control the entry of silt into the canal and to
control the deposition of silt at the head of canal.
 To control the fluctuation of water level in the river
during different seasons.

5. The following points should be considered to select a
site for this diversion headworks.
 The river should be straight and narrow at the site
 The elevation of site should be higher than the area to
be irrigated for gravity flow.
 River banks at site should be well defined and stable.
 Valuable land upstream of the barrier like weir or
barrage should not be submerged.

6.  Material of construction should be locally available.
 Roads or railway communication to the site is essential
to carry the material of construction.
 Site should be close to the cropland to minimize loss of
water due to seepage and evaporation of canal.
 The site should provide a good foundation for
construction of weir or barrage.

8. The components of diversion headworks are:
 Weir or barrage
 Canal head regulator
 Divide Wall
 Fish Ladder
 Scouring Sluices Under sluices
 Silt excluder
 Silt ejector.
 Marginal embankment or dikes
 Guide bank
 Silt pocket or trap.

9. 1.Weir
It is a solid obstruction placed across the river. Its main
function is to raise the water level so that water can be
diverted by canal to crop field due to difference of head.

11. Barrage is practically a low weir with an adjustable
gate over this low weir. Heading up of water is
affected by gate.

14. 1.Vertical Drop Weir(Masonry Weir)
 A crest gate may be provided to store more water
during flood period.
 At the upstream and downstream ends of impervious
floor cut off piles are provided.
 Launching apron are provided both at upstream and
downstream ends of floor to safeguard against
scouring action.
 A graded filter is provided immediately at the
downstream end of impervious floor to relieve the
uplift pressure.
 This type of weir is suitable for any type of
foundation.

16.  This type is suitable for soft sandy foundation.
 It is used where difference in weir crest and
downstream river bed is not more than 3 m.
 Hydraulic jump is formed when water passes over the
sloping glacis.
 Suitable for soft soil foundation.

17.  In rock fill type weir, there are no of core wall on D/S of main
weir wall and space between weir wall is filled with rock
fragments that’s why it is called as Rock fill Weir.
 Requires large quantity of rock fragments so it is economical
when rock are available easily in surrounding region.
 Suitable for fine sand foundation.

18.  Structure at the head of canal taking off from a reservoir may
consist of number of spans separated by piers and operated by
gates.
 Regulators are normally aligned at 90° to the weir.
 These are used for diversion of flow.
 Silt reduces carriage capacity of flow.

19.  Provides platform for bridges for communication facility.
 To maintain constant supply in off tacking canal during
low Discharge Period.
 To cut off the Discharge of parent canal during
maintenance on D/S side.

20.  The Divide Wall is a long wall constructed at right angle to
the weir or barrage, it may be constructed with stone masonry
or cement concrete.
 On the upstream side, the wall is extended just to cover the
canal regulator and on the down stream side, it is extended up
to the launching apron.
 The functions of the divide wall are as follows,
1. To form a still water pocket in front of the canal head so that
the suspended silt can be settled down which then later can be
cleared through the scouring sluices from time to time.
2. It controls the eddy current or cross current in front of the canal
head.
3. It provides a straight approach in front of the canal head.
4. It resists the overturning effect on the weir or barrage caused by
the pressure of the impounding water.

21.  The Scouring sluices are the openings provided at the
base of the weir or barrage at lower level.
 It is provided at same side on which off tacking canal
is located.
 The crest of under sluices is kept lower than crest of
weir due to which water is attracted towards sluice
which helps to easy diversion of water in to canal.

22.  The Fish Ladder is passage provided adjacent to divide
wall for the movement of fishes from U/S to D/S and
vice-versa.
 In general, the tendency of fish is to move from
upstream to downstream in winters and from
downstream to upstream in monsoons. This movement
is essential for their survival.
 In the fish ladder, the baffle walls are constructed in
the zigzag manner so that the velocities of flow within
the ladder does not exceed 3 m/s

24.  Silt excluder is the structure
provided in still pocket to pass silt
content water in D/S .
 This is helps to allow clear water
entry in canal.
 Water contains silt is having high
density so it is always near to bed
level.
 The tunnel nearest to the head
regulator is longest, and the
successive tunnels decrease in
length, the tunnel nearest to the
divide wall is shortest.
 The tunnels are covered by R.C.C.
Slab.
 The top level of the slab is kept
below the sill level of the head
regulator.
 So, the completely clear water is
allowed to flow in the canal
through the head regulator.

25.  Silt ejectors, also called silt
extractors, are those devices
which extract the silt from the
canal water after the silted
water has traveled a certain
distance in the off-take canal.
 These works are, therefore,
constructed on the bed of the
canal, and little distance
downstream from the head
regulator.
 It consist of tunnels parallel to
flow of canal and turns in to 90
to eject silt.
 The length provided may be
different.

26. THANK YOU