In this report, I write about the How we operate barrage, components of barrage and the working of silt controlling devices with the design

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1. Introduction
1.1 Barrage
A barrage is a type of low-head, diversion dam which consists of a number of large gates that can
be opened or closed to control the amount of water passing through the structure, and thus regulate
and stabilize river water elevation upstream for use in irrigation and other systems.
1.2 Design of Barrage
The design of any hydraulic structure comprises of two steps:
 Hydraulic design, to fix the overall dimensions and profiles of the structure.
(Dimensions are usually fixed by empirical formulae)
 Structural design, where the various sections are analyzed for stresses under different loads
and reinforcement or other structural details are worked out.
1.3 Components of Barrage
1. Divide wall.
2. The fish ladder.
3. Sheet piles.
4. Inverted filter.
5. Flexible apron.
6. The under sluices.
7. River training work.
8. Guide banks.
9. Marginal bunds.
10. Groans or spurs.

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Main barrage portion:
a. Main body of the barrage, normal RCC slab which supports the steel gate.
b. Upstream concrete floor, to lengthen the path of seepage and to project the middle portion
where the pier, gates and bridge are located.
c. A crest at the required height above the floor on which the gates rest in their closed position.
d. Upstream glacis of suitable slope and shape. This joins the crest to the downstream floor
level. The hydraulic jump forms on the glacis since it is more stable than on the horizontal
floor, this reduces length of concrete work on downstream side.
e. Downstream floor is built of concrete and is constructed so as to contain the hydraulic
jump. Thus it takes care of turbulence which would otherwise cause erosion. It is also
provided with friction blocks of suitable shape and at a distance determined through the
hydraulic model experiment in order to increase friction and destroy the residual kinetic
energy.
Divide Wall
 A wall constructed at right angle to the axis of the weir separating the weir proper from the
under sluices (to keep heavy turbulence at the nose of the wall, well away from upstream
protection of the sluices)
 It extends upstream beyond the beginning of canal HR. Downstream it extends up to the
end of loose protection of under sluices launching apron)
 This is to cover the hydraulic jump and the resulting turbulence.

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The fish ladder
 For movement of fish (negotiate the artificial barrier in either direction)
 Difference of level on the upstream and downstream sides on the weir is split up into water
steps by means of baffle walls constructed across the inclined chute of fish ladder.
 Velocity in chute must not be more than 3m/s
 Grooved gate at upstream and downstream - for effective control.
 Optimum velocity 6-8 ft/s
Sheet piles:
Made of mild steel, each portion being 1/2' to 2' in width and 1/2" thick and of the required length,
having groove to link with other sheet piles.
Upstream piles:
Situated at the upstream end of the upstream concrete floor driven into the soil beyond the
maximum possible scour that may occur.
Functions:
1. Protect barrage structure from scour
2. Reduce uplift pressure on barrage
3. To hold the sand compacted and densified between two sheet piles in order to increase the
bearing capacity when barrage floor is designed as raft.
Intermediate sheet piles:
 Situated at the end of upstream and downstream glacis. Protection to the main structure of
barrage (pier carrying the gates, road bridge and the service bridge) in the event of the
upstream and downstream sheet piles collapsing due to advancing scour or undermining.
They also help lengthen the seepage path and reduce uplift pressure.
 Downstream sheet piles: Placed at the end of downstream concrete floor. Their main
function is to check the exit gradient. Their depth should be greater than the possible scour.
Inverted filter:
 Provided between the downstream sheet piles and the flexible protection. Typically 6"
sand, 9" coarse sand and 9" gravel. Filter may vary with size of particles forming the river
bed. It is protected by placing over it concrete blocks of sufficient weight and size. Slits
are left between the blocks to allow the water to escape.
 Length should be 2 x downstream depth of sheet.
Functions:
 Check the escape of fine soil particles in the seepage water.

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Flexible apron:
 Placed downstream of the filter
 Consists of boulder large enough not to be washed away by the highest likely velocity
 The protection provided is enough as to cover the slope of scour of 1 1/2 x depth of scour
as the upstream side of 2 x depth of scour on the downstream side at the slope of 3.
The under sluices: scouring sluices
Maintaining a deep channel in front of the Head regulator on the downstream side.
Functions:
1. As the bed of under sluice is not lower level than rest of the weir most of the day whether
flow unit will flow toward this pocket easy diversion to channel through Head regulator
2. Control silt entry into channel
3. Scour the silt (silt excavated and removed)
4. High velocity currents due to high differential head.
5. Pass the low floods without dropping
6. The shutter of the main weir, the raising of which entails good deal of labor and time.
7. Capacity of under sluices:
8. For sufficient scouring capacity, its discharging capacity should be at least double the canal
discharge.
9. Should be able to pass the dry weather flow and low flood, without dropping the weir
shutter.
10. Capable of discharging 10 to 15% of high flood discharge
Guide banks:
Earthen embankments => stone pitching. Force the river into restricted channel, to ensure almost
axial flow near the weir site. (Embankments in continuation of G-Banks. To contain flood within
flood plains)
Marginal Bunds:
Provided on the upstream in order to protect the area from submergence due to rise in HFL, caused
by afflux.
Groans or spurs:
 Embankment type structures constructed transverse to river flood, extending from the
banks into the river (also transverse dykes).
 Protect the bank from which they are extended by deflecting the current away from the
bank.

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1.4 Function of Barrage:
1 To maintain and control the flow of water in the river.
2. It regulate and stabilize river water elevation upstream for use in irrigation and other
systems.
3. It is used for transportation purpose.
4. Flood control.

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2. Operation and Regulationof Barrage
2.1 Introduction
A barrage is such a structure that has gates for controlling flow across almost the whole river
section with their crest levels being very close to the riverbed. Hence operation of any gate or
groups of gates not only affects the flow pattern in the upstream, that is, in the pool and in the
downstream but also the river bed level changes associated with the changes in flow velocity.
Further the under sluice bays have to be operated in such a way that there is not significant entry
of silt into the off-taking canal. In order to prevent any unnatural flow behaviour and river
morphological changes while satisfying the requirements of maintaining the pond level and
prevention of sediment entry into the canal, a set of general guidelines have been formulated.
Some of the important ones amongst these have been enumerated below:
1. The required pond level is to be maintained both during the non-monsoon flows and the falling
flood periods.
2. The non-monsoon flows remain as far as possible near the undersluice bays so that feeding of
the canal through a head regulator is not affected. In order to achieve this, therefore, most of
the spillway bays are kept shut or opened very marginally. It is only the undersluice bays that
operate and pass most of the river discharge which, in turn, creates a deep channel in the
riverbed towards the bank where the canal is off-taking.
3. Though it is essential to draw water towards the canal head regulator side by operating the
undersluices, it is also to be seen that a fairly uniform distribution of discharge takes place
along the width of the barrage, as far as possible.
4. The gate operations should be such that the risk of deep scours or shoal formations (that is,
deposition of sediments to form mounds) in the vicinity of the barrage both on the upstream
and downstream is minimized, as far as possible. In order to achieve this, it is essential that the
gate openings of adjacent bays should not be abruptly different.
5. A gate opening sequence has to be evolved such that deposition of silt and debris is avoided as
far as possible on the upstream pool.
6. On the downstream of the barrage structure, the hydraulic jump should not be allowed to form
beyond the toe of the downstream glacis.
7. A relatively high intensity of flow is to be avoided in the regions of deep scour, if any has been
formed.
8. If a shoal has formed on either upstream or downstream it has to be washed out by an appropriate
gate opening sequence.
9. The gate operation schedule should also consider the safe rate of lowering or rising of the
pond level.
The operation and regulation of barrage gates can be divided into three distinct periods
2.2 Pre-Monsoon Operation
This is a low flow period and wastage of water has to be avoided during this time, as far as
possible. The barrage gates shall have to be regulated such that all the available supplies are
conserved and pond level is maintained. Any excess flow over and above the requirements
through the head regulators have to be released through the undersluice bays and silt excluder
tunnels, wherever provided. The releases through the head regulator of the canal have to be based

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on the accepted discharge formula. For ready reckoning they are usually converted to discharge
tables. These tables have to be occasionally checked for accuracy by taking actual measurement
of flows in the canal. For any flashy flood, the canal may have to be closed temporarily, if the
concentration of suspended sediment is in excess of the safe prescribed limits.
2.3. Monsoon Operation
Gauges to indicate flood stage have to be installed sufficiently upstream (about a kilometer or
more) of the barrage at suitable location so as to ensure adequate margin of time for operation of
gates at the barrage site. In order to create most favourable conditions for sediment exclusion from
the canal, “Still-Pond” regulation have to be adopted, as explained below. However, in locations
where the canals cannot be closed for silt removal, “semi-still-pond” regulation have to be adopted.
These two modes of operation are explained below.
2.3.1. Still Pond Operation
In still pond operation, all the gates of the undersluice bays have to be kept closed so as to limit
the discharge flowing into the pocket to be equal to the canal withdrawal. The specified or required
discharge only should be drawn into the canal and the surplus river discharge should be passed
through the spillway bays or river sluice bays, if provided. As the undersluice bays are kept closed,
the low velocity in the pocket causes the sediment to settle down and relatively clear water enters
the canal. However, the pocket gets silted up in this process after sometime.
At that time the canal head regulator gates should be closed and the deposited silt should be flushed
out by opening the gates of the undersluice bays. The canal supply may be stopped during this
scouring operation which may take about 24 hours. After the deposited silt has been flushed out
sufficiently, the head regulator gates should be opened and undersluices closed. This operation is
desirable where the crest of the head regulator is at a sufficiently higher level than that of the
upstream floor of the undersluice bays. This still pond operation should be continued till the river
stage reaches the pond level after which the undersluice gates should be opened to avoid
overtopping.
2.3.2. Semi-still Pond Operation
In the semi-still-pond operation, the gates of the canal head regulator are not closed for flushing
of the silt deposited in the pocket. The gates of the undersluice bays should be kept partially open
to the minimum necessary so that the bed material in the pocket could be passed downstream. The
discharge in excess of the canal requirement should be passed through the undersluice bays and
silt excluder tunnels, wherever provided.
During the monsoon months, it is important to keep a constant watch over the sediment entering
the head regulator, a portion of which may have to be discarded through a sediment-extractor, if
any, provided within the canal. Further, it may have to be ensured that sediment deposition takes
place only to the extent that can be washed out early in the cold weather before the full demand
develops. For these conditions to satisfy, the following actions may be necessary:
1. Sediment charge observations for both suspended sediment and bed load have to be made
at least once a day in low floods immediately below the head regulator, below the silt
ejector, if any, and at any other sensitive point lower down the canal. The frequency of
observations may have to be increased in medium and high floods as required.

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2. The cross section of the canal shall have to be taken at a few critical points to keep a
watch on the extent of sediment deposition in the canal.
3. Water surface slopes at the critical points in the head reaches of the canals have to be
kept under observation with the help of gauge observations of water levels.
4. The ponding upstream of power stations, for the case of power channels, shall have to be
restricted to the requisite extent so as to avoid harmful sediment deposition.
2.4. Post Monsoon Operation
The sediment concentration observations and cross section of the critical points on the canal have
to be continued but at less frequent intervals till satisfactory conditions have been established. Still
or semi-still pond operation, with sediment excluders or sediment extractions, depending on the
surplus water available, have to be continued till the water becomes reasonably clear.
When a canal is first opened, a low supply have to run for a few hours at least and the depth should
gradually be raised according to the requirements. The rate of filling and lowering of the canal
should be prescribed and these should not be transgressed.
If a study of the survey data indicates that shoal formation has occurred on the upstream or on the
downstream of the barrage in spite of a judicial operation of gates, during normal and flushing
operation of the pool, the shoal have to be removed by dredging to the extent possible so that
satisfactory flow conditions are established and also the desired capacity is restored.
Satellite imageries may be studied to detect significant changes of the bank-lines for over the
past years and remedial measures taken to improve the river behaviour.

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3. Silt Control Devices
The entry of silt into a canal, which takes off from a Head-Works, can be reduced by
constructing, certain special works, and called silt control works. These works may be
classified into the following two types;
3.2.1. Silt Excluder
Silt excluders are those works which are constructed on the bed of the river, upstream of the
head regulator. The clearer water enters the head regulator and the silted water enters the silt
excluder. In this type of works, the silt is, therefore, removed from the water before it enters
the canal.
Description and Design of a Silt Excluder:
A silt excluder consists of a number of rectangular tunnels running parallel to the axis of-the
head regulator and terminating near the under-sluiced weir. The tunnel nearest to the crest of
the head regulator has to be at least of the same length as the head regulator. Other tunnels may
be shorter in length. The roof slab of the excluder tunnels is kept at the same level as that of
the regulator crest, as shown in Figure.
The bottom layer of water which is highly charged with silt and sediment will pass down the
tunnels and escape over the floor of the under-sluice way, since the gates of the under sluice
way shall be kept open up to the top of the tunnels. The clearer water over the top of the roof

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of the excluder tunnels, will thus enter the canal through the head regulator. Usually, two or
three bays of the 'under-sluices of the weir or the barrage are covered by the excluder. However,
excluder covering only one bay has been designed and is usually adopted for sandy rivers.
Design of tunnels. A theoretical design, of a silt excluder is confined mainly to find out the
area of the tunnel openings required to pass the designed discharge and to determine its
structural requirements. On the basis of past experience and model studies, the design of an
excluder is finalized. The Punjab Irrigation Research Institute has carried out extensive
.research in the design of excluders. Based on their research findings, it has been found that if
the excluder discharge is restricted to 15 to 20% of the canal discharge, satisfactory silt
exclusion can be obtained. A minimum velocity of 2 to 4.5 m/sec must be maintained through
the tunnels in order to keep them free from sediment. A value of 3 m/sec is usually adopted for
ordinary straight reaches. A higher value of 4 to 4.5 m/sec may be adopted for boulder-stage
rivers. A lower value of about 2 m/sec may be adopted for sandy rivers. After fixing the
discharge and velocity, the cross-sectional area of the excluder tunnel-openings, can .be
determined. Knowing the height, the required width can be found and divided into a suitable
number of bays.
By model studies, it has been found that the tunnels should be located at selected positions;
rather than distributed uniformly over the entire length of the regulator. The position of tunnels
being more important than their number. River curvature must be taken into consideration as
far as possible. It was found by experience at Khanki that three tunnels were more efficient
than six. Also, a smaller number of pocket bays covered by the excluder, give better results as
do the openings of the tunnels confined to the mouth. Side openings into the tunnels, have been
found to decrease the efficiency. Usually, 4 to 6 tunnels are generally provided.
Approach and exit: At the entrance, the tunnels are generally given a bell mouthed shape so
as to increase the zone of suction. The radius of bell mouthing varies from 2 to 6 times the
tunnel width the radii increasing for tunnels away from canal head regulator and for shorter
tunnels. At the exit end, the tunnels are throttled for restricting the discharge to the desired
value and to increase the velocity to prevent deposition of silt.
Height of tunnels: The height of tunnels generally varies from 0.5 to 0.6 m for sandy rivers,
and 0.8 to 1.2 m for boulder stage rivers.
Body and roof of tunnels: The roof of tunnels must be strong enough to withstand the full
water load coming from its top, with no water inside. Such a condition may arise when the
tunnels are closed from upstream for repairs or for some other purpose. Moreover, the tunnel
walls and roofs must be strong enough, as not to be, damaged by debris, boulders, shingles,
etc., during floods. This is all the more important, since damage to excluder is not discovered
as they are always under water and difficult to repair. Moreover, even .the slight damage to the
tunnel roof has found to have made the excluder less efficient.
Outfall channel: It should also be ensured that a channel to take the silt laden water into the
river is maintained downstream of the .excluder. No separate outfall channel is generally
required for sandy rivers as a continuous flow through the alluvial bed, itself makes a channel

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there. However, if gravel and boulders are to be excluded and the main channel is away, a lined
channel may be necessary, or a channel may have to be created by suitable training measures.
This was done in the case of Tajewala Head Works on Yamuna river, where two short spurs
induced the river to flow· on the side of the under-sluices, and thus eliminated the construction
of a separate outfall channel.
Losses in tunnels: The following head losses may be taken into account for calculating the
tunnel sections:
1. Frictional losses
2. Loss due to bend
3. Transition loss due to change of velocity in contraction.
4. Transition loss due to change of velocity in expansion.
3.2.2. Silt Ejector
Silt ejectors, also called silt extractors, are those devices which extract the silt from the canal-
water after the silted water has travelled a certain distance in the off-take canal. These works
are, therefore, constructed on the bed of the canal, and a little distance downstream from the
head regulator.
Description and Designof Silt Extractor or a Silt Ejector: The typical layout of a silt ejector is
shown in above figure.
It essentially consists of horizontal diaphragm slab, a little distance above the canal bed, which
separates out the bottom layers. Under the diaphragm, which is normally spanning the entire width
of the canal, there are tunnels or compartments which extract the highly silted bottom water into

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an escape channel. The tunnel entrances should be designed in such a way that there is no
disturbance of flow at entry, and the escape flow is quickly accelerated under the diaphragm, so as
to prevent the clogging of tunnels. These objectives are achieved by dividing the entire span width
into a number of compartments or tunnels by means of streamlines vanes.
Location: The silt ejector should be located in the canal neither too much near the head regulator
nor too far away from the head regulator. In the former case, the residual turbulence may keep the
silt in suspension, and thus, preventing its extraction up to the desired extent. Similarly, in the
latter case, when the ejector is located far away from the head regulator, the silt may settle down
earlier and reduce the channel capacity upstream, thus, defeating the very purpose of the ejector.
Design Principles for Various Components are given below
1) Approach channel
The normal main canal section is generally widened after the canal takes off from the head
regulator, so as to reduce the flow velocity to a desired level. This will help in increasing the silt
concentration in the bottom layers. The reduced velocity should be maintained for a sufficient
length to achieve the desired sediment concentration in the bottom layers.
2) Diaphragm
The diaphragm should be placed in such a way that it causes least disturbance in front of the ejector
tunnels, so as .not to disturb silt concentration attained in the bottom layers. The diaphragm is
generally placed at the downstream bed level of the canal, i.e. the canal bed has to be slightly
depressed under the diaphragm. However, if the diaphragm has to be placed higher due to some
other considerations, the condition of fall, particularly for low Supplies, should be checked, and
energy dissipation arrangements made, if found necessary. The diaphragm should be properly tied
to the supports, so as to prevent it from being dislodged.
3) Tunnel
The tunnels or compartments shall be constructed by gradually converging vanes, as explained
earlier. The upstream noses of the vanes and piers may have cut-water· shapes, while the
downstream end of vanes may be fish-tailed. The tunnel dimensions at the entry and exit may be
so fixed, as to ensure velocities that would carry the size of sediment to be removed. The section
of the sub-tunnels at the entry may be so chosen that the velocity of flow at the intake is slightly
higher than the velocity of bottom filaments of water upstream of ejector. The section of sub-
tunnels up to their exit, where they end into the main tunnels, may be reduced gradually in such a
way that there is an overall increase of 10 to 15 per cent in the velocity of emerging flow.
At the exit of sub-tunnels, the section of the main tunnel may be designed such that the flow
velocities of the combined discharge are not less than the velocities emerging from the sub-tunnel.
The section at the exit of main tunnels may be so designed, as to attain a velocity 2.5 to 6 m/sec
depending on the grade of sediment to be ejected, but in all cases, the exit velocity has to be more

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than the critical velocity, so as to ensure super-critical flow. The height of the tunnels is generally
kept from 0.5 to 0.75 metres.
4) Gate control regulation
The discharge from ejector is controlled by gated regulation at the downstream end of the tunnels.
The amount of discharge passing down the ejector and the frequency of its operation would vary
in different parts of the year depending on the silt load carried by the canal. Proper gate regulation
is, therefore, required, as per the intelligence and initiative of the maintenance engineers. The gate
must be operated occasionally, so as to ensure it to be in working order.
5) Escape channel and Escape Discharge
The outflow from the ejector is taken to a natural drainage through an escape channel. The escape
channel should be designed to have a self-cleansing velocity, so that the ejected material is
transported without deposition. Adequate fall between the F.S.L. of the escape channel at its tail
end and the normal H.F.L. of the natural drain, is desirable for efficient functioning of the channel.

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4. Conclusion
In this study effort has been given to prepare an operation rules for barrage to relate upstream and
downstream water level of barrage with gate opening. Sedimentation and morphological factors
plays a vital role on the operation schedule. Some aspects of morphological behavior specially
affect of still pond and semi open operation systems on sedimentation and morphology has been
analyzed. Various data such as water level, discharge, river cross sections and flow required for
operation rule for barrage gate.
Silt control devices plays a vital role at the time of sedimentation and silting takes placed. We are
used the silt excluder as well as silt excluder depending on the various conditions. The silt excluder
is placed parallel to head regulator, it prevents to passing the silt into the canal. The silt ejector is
placed at downstream side, some distance from the head regulator in the canal when the water
comes with silt into the canal. The silt ejector is help to remove the silt from the canal and
maintained the free flows.

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5. References
 BWDB (1999), “Operation and Maintenance Manual of Teesta Barrage and Its Canal Head
Regulator”, Final Report, Chapter 9, Page 1-5.
 Garg, S. K. (2006), “Irrigation Engineering and Hydraulic Structures”, Khanna Publishers,
19th edition, Page 952-955.
 IS 6996 (part 1): 1989, Hydraulic Design of Barrages and Weirs- Guidelines.
 IS 6531:1992, Design of Sediment excluders-Guidelines.
 IS 7496:1974, Critesria for Hydraulic Design of Silt Selective Head Regulator for Sediment
control in off-taking Canals