Canal Structures

1. Head regulator2. Cross regulator

3. Canal Escape4. Canal Fall

5. Irrigation outlets6. Silt Ejector

Head Regulator Functions Cons.1.Branch Canal2.Take off points

1.Regulate the water from parent /reservoir canal to branch canal2. To control entry of silt3.Use as meter

1. Components depend upon size and location.2. Consists of gated rectangular opening

Cross Regulator Functions Cons.1.To maintain the necessary depth on u/s.2.Constructed along main canal3.Constructed at off take of canal4. Distance Main 9to 10 kmBranch c/c 6 to 10 km

1.To control flow2. To feed off taking canal3.To provide road way

1.abutements with grooves and piers are constructed2. Silt of regulation kept higher than bed level of canal.3. Gates are fitted in grooves4. Combined with fall called fall regulator.

Canal escape Functions Cons.1. to escape extra water from the canal into some natural drains2.located at 5m to 10 mc/c along length of main canal near natural drain

1.wasting some of its supplied water 2. To feed off taking canal3.To provide road way

1. canal scouring escape- scoring the excess of silt from time to time2. surplus escape constructed to dispose of excess supplies of parent canal

Silt ejector Functions Cons.1 these are the divices which extract silt from canal water after silted water has travelled a certain distance2. constructed on the bed of canal3. excluder is preventive measure4. constructed from some distance apart from head

1.to extract silt 1. consists of horizontal Diaphragm placed above the canal bed2. canal bed is depressed below the diaphragm so that the height of silt tunnel below the diaphragm is 0.5 to .8m3. diaphragm wall separates the top water level from the bottom water obtaining silt4. the discharge through the tunnel are governed by gate opening of the escape tunnel5. escape channel is given a steeper slope so that

regulator silt is discharged back to the river

Falls:

1. Downstream of the takeoff canal2. To lower the bed level when the slope of the ground is steeper

fall rapid SteppedIf lowering of the canal bed is achieved at one section vertically downwards, the structure is called fall or drop

Achieved by the providing slopping ramp of same length is called as rapid fall

Instead ramp the steps are provided in continuation

Function:

1. To lower the canal bed level according to the slope of ground2. To maintain the design bed slope

Classification:

1.

2. Vertical a. Simple regulator fallb. Trapezoidal notch fall

3. Glacis type fall

4. Ogee 5. Rapid6. Stepped 7. Notch

Vertical:

The difference between u/s FSL and d/s FSl should not more than 1.2m

Suitable for 15 cumecs of discharge

Glacis type:

Notches are provided

Suitable for greater discharge

Ogee fall

First constructed by sir Proby Cautly on the ganga canal

It has gradual convex and concave curves to provide smooth transitions and to reduce the disturbance

This preserve the energy due to this ogee fall has defects:

1. Considerable drop down effect on u/s resulting in bed erosion2. Formation of the hydraulic jump is not possible until the sufficient depth scouring is not achieved

Rapid fall:

These were provided on western Yamuna coasts

Consists of glacis slopping 1 v : 10 to 20H

Long glacis assorted the formation of hydraulic jump

Construction cost is high due to gentle slope

Notch fall:

Construction-

Fall consist of one or more trapezoidal notch in high crested wall

Flat circular lip is provided to disperse the water projects d/s

Notches were designed to maintain normal water depth in u/s channel

Neither drawdown nor heading up of water

It can be used as regulator

Purpose of providing canal fall-

To avoid heavy banking

To maintain the design bed slope

Gives consideration in economy

Depth, discharge relationship can be maintained

Standing wave flume:

Construction:

An approach with rising floor

Conversing section with horizontal floor

A throat

A diverging section again with rising floor

Guage wells

For small discharge notches are used

Fitted with head regulator

Irrigation Outlets:

Outlets are the structures constructed to admit the water into water courses and field channels

Functions:

To admit water from distributaries or parent canal to minors

To draw proportionate quantity of silt to measure

The discharge release in the field channel

Requirements of good outlet

A constant discharge irrespective of variation of levels in the parents canal and the water course

Should be simple in construction and maintenance

It should be strong, cheap

It should draw Proportionate silt loading

Classification of silt

1. Simple or non-modular or pipe2. Modular outlet3. Rigid module4. Semi rigid 5. Flexible

Simple or non-modular or pipe:

Consist of pipe fixed below the bank at a level 15 to 20cm below the FSL

Sliding gate is provided

Discharge depends upon the water level in the parent canal

Modular outlet:

Constant discharge at the field channel

Rigid module:

Designed by Gibbes Punjab irri. Dept.

Cosists of pipe having a bellmouth

Water directed to the eddy chamber through 1800

Rising spiral pipe in which free circular flow is developed

In which product of velocity and raius is constant

In eddy chamber baffle plates are fixed with their lower edges slopping at required heights above the silt of outlet

Discharge is kept constant

Water discharges into a spout from the eddy chamber and further into the water course