training programme on engineering designs-canal structures general design principles canals

TRAINING PROGRAMME ONTRAINING PROGRAMME ON

ENGINEERING DESIGNS-CANAL STRUCTURESENGINEERING DESIGNS-CANAL STRUCTURES

GENERAL DESIGN PRINCIPLES GENERAL DESIGN PRINCIPLES

CANALS CANALS

BY BY

ROUTHU SATYANARAYANAROUTHU SATYANARAYANA

CHIEF ENGINEER (Retired.)CHIEF ENGINEER (Retired.)

FORMER ADVISOR, GOVERNMENT OF A.PFORMER ADVISOR, GOVERNMENT OF A.P

Canal & Design PrinciplesCanal & Design Principles

Introduction: Irrigation is the process of artificially supplying water to soil

for raising crops. It is a science of planning and designing an

efficient, low cost, economic irrigation system tailored to fit

natural conditions.

It includes the study and design of works in connection with

river control, drainage, and hydraulic power generation.

The source of water for irrigation is precipitation.

Artificial irrigation can be divided into lift irrigation and flow

irrigation.

Irrigation schemes consist of storage or diversion structures

and canal distribution system.

Canal & Design PrinciplesCanal & Design Principles Introduction: The NagarjunaSagar Scheme (NSS) is a multipurpose project,

comprising a dam across the river Krishna and two main canals, one on either flank of the river. Besides providing irrigation water supplies to 8, 95,547 ha of parched lands.

It is the largest and highest stone masonry dam in the world. The construction of the dam was commenced in 1957 and completed

by 1970. Erection of Spillway radial gates was completed during 1973-74. The dam comprises 1450m long gravity masonry dam flanked by

2560m long earth dam on the left side and 853m long earth dam on the right side.

The maximum height of the main dam above the deepest bed level of +59.74m is 124.66m. The top of the dam is +184.40m in masonry dam and +185.93m in earth dam portions.

The Spillway is 471m long with crest level at +166.420m and top of the 26 numbers of radial crest gates of size 13.72m x 13.41m each is at +179.83m.The Spillway can tackle a maximum flood discharge of 45,306 cumec (1.60 million cusec).

Canal & Design PrinciplesCanal & Design Principles Introduction: Nagarjunasagar canal system: The NagarjunaSagar Canal System is one of the largest in India.

• Two canals run on contour, take off from each flank.____________________________________________________________________

Detail Jawahar canal Lal bahadur canal____________________________________________________________________

1. Command area in Hectares 4 75 304 Ha. 4 20 243 Ha.2. Length in Kilometers (Kms.) 203 297 including

117 long 21st Branch3. Branch canals in Kms 269 (9 nos) 1984. Distributaries in Kms 5342 77225. Field Channels in Kms 14 400 96546. No. os blocks 22 21 + 117. Water allocation 132 TMC 132 TMC8. Water release 4th August, 1967

Smt. Indira Gandhi, PM

____________________________________________________________________

Canal & Design PrinciplesCanal & Design Principles Introduction:Introduction: Existing deficiencies in the Canal system• The canal system is in a damaged condition due to insufficient The canal system is in a damaged condition due to insufficient

maintenance over the past several years. maintenance over the past several years. • The distribution system, particularly, is in a bad shape, and have The distribution system, particularly, is in a bad shape, and have

lost their designed carrying capacity. lost their designed carrying capacity. • Several structures and canal lining have been damaged. Several structures and canal lining have been damaged. • The shutters of the OTs are either inoperable or not available. The shutters of the OTs are either inoperable or not available. • Extensive growth of vegetation and plants inside the canal prism. Extensive growth of vegetation and plants inside the canal prism. • It is impossible to approach the system for inspection and It is impossible to approach the system for inspection and

maintenance. maintenance. • There have been recurrent breaches and slips in several There have been recurrent breaches and slips in several

vulnerable embankment reaches. vulnerable embankment reaches. • The deep cut reaches have suffered extensive damages due to The deep cut reaches have suffered extensive damages due to

slope slips/rock falls, collapsed lining etc. slope slips/rock falls, collapsed lining etc. • The net result of these deficiencies is that there is significant The net result of these deficiencies is that there is significant

reduction in the irrigated area in the command area.reduction in the irrigated area in the command area.

Canal & Design PrinciplesCanal & Design Principles Introduction: The Government of Andhra Pradesh has taken up Rehabilitation and

Modernization of Nagarjunasagar Scheme under Andhra Pradesh Water Sector Improvement Project (APWSIP) with the World Bank Financial Assistance.• The APWSIP has the following four components:

(i). Component A: Improving irrigation service delivery and management

(ii). Component B:Irrigated agriculture intensification and diversification:

(iii). Component C: Water sector institutional restructuring and capacity

building:(iv). Component D:

Project Management: Component A

• The following two sub components are part of the component - A(i). Sub- component A-1:

Participatory rehabilitation and modernization of Irrigation system.

(ii). Sub- component A-2:Dam safety works.

Canal & Design PrinciplesCanal & Design Principles Introduction:

(A). The rehabilitation works will comprise the following:• Removal of silt, vegetation, bushes and plants within the canal

prism and bank• Resectioning of canals and strengthening of banks,• Resectioning of canal banks to bring the top width of banks to

acceptable design standards,• Treatment of sub-grade with cohesive non-swelling soils in the

reaches associated with swelling black cotton soils,• Mechanized placement of CC lining in vulnerable canal reaches and

providing protective CC lining on upstream and downstream of canal structures,

• Repairs/ replacement of damaged canal structures.• Repairs/replacement of damaged / non-functional mechanical and

electrical fixtures, gates and equipment.

• Remodeling of majors and minors to original designs standards and providing CC lining,

• Implementation of remedial measures in the deep cut reaches of main canals,

• Providing additional cross regulators in the 21st main branch canal,• Improvement of inspection roads on canal banks,

( cont….)


Introduction:

(B). The modernization works will comprise the

following:

• Construction of measuring devices in main canals, branch

canals, majors, and in the entire distribution system (minors/

sub – minors),

• Providing proportional distributor structures for designed

flow of water into the minor/sub-minor without gates and

installation of APM outlets,

• Introducing motorized operation of gates to the optimum

possible extent on important structures,

Canal & Design PrinciplesCanal & Design Principles Introduction:

(C). Lift Irrigation Schemes• Repairs will be carried out to the civil work and electro- mechanical

equipment including replacement of some pumping equipment of

the existing lift irrigation schemes on Jawahar Canal and Lal

Bahadur Canal.

(D). Supplementation Schemes• It is proposed to utilize the seepage/regenerated water in the

command area for supplying to the tail end areas in the gap ayacut

through construction of suitable diversion schemes.

Consultancy:• M/S SMEC International Pty Limited, Australia in association with

M/S SMEC (India) Pvt. Limited, Gurgaon have been appointed by

Government of Andhra Pradesh as Consultants for Engineering

Design for Rehabilitation and Modernization of NSS under APWSIP.

Canal & Design PrinciplesCanal & Design Principles Introduction: Consultancy:

The main tasks and activities are as follows:(i). To chalk out the programme for preparation of design/drawings

and construction drawings in consultation with CE, NSP.(ii). To review the original design parameters (hydraulic and

structural) adopted for canals and canal structures (main canals, branch canals, major and minor distributaries) and to provide revised design/drawings, ensuring that the original designed canal capacities for the canal network is maintained.

(iii). To prepare the design/drawings for the new structures, wherever required and for the damaged structures requiring large scale modification in the structural designs based on the field and other relevant data supplied by the Department and also to prepare construction drawings for these structures, in accordance with relevant IS Codes.

(iv). To prepare package wise construction drawings for canals and canal structures, which are included in the Rehabilitation and Modernization packages of canal system and Dam Safety Works packages.

(Cont….)

Canal & Design PrinciplesCanal & Design Principles Introduction: Consultancy:

The main tasks and activities are as follows:

(v). To prepare design/drawings for dam safety works based on the recommendations of Dam Safety Review Panel (DSRP) in consultation with C E, NSP and CE, C. D. O.

(vi). To prepare type designs of canal sections and canal structures to each hydraulic reach of distributary system to suit different sub-grade conditions.

(vii). To prepare design of hydro-mechanical works and to check designs/ drawings and specifications submitted by manufactures/ contractors for hydro- mechanical works.

(viii) .To impart training to the APWSIP personnel, based on the training programme to be structured in consultation with the Department.*

(ix). To computerize all design/drawings and relevant data for record and further reference and to keep the record of hard copies of design/drawings.


Introduction:

The canal structures can be divided into the following

categories based on their functional requirement.

(i). Cross drainage structures

(ii). Control structures

(iii). Communication or service structures

(iv). Flow measurement structures

Cross Drainage (CD) & Cross Cross Drainage (CD) & Cross Masonry WorksMasonry Works

Definition:

Works which are constructed at the crossing of natural drain or stream or

a canal, so as to dispose of the drainage water without interruption of

canal supplies are known as Cross Drainage (CD) works.

• Structures Carrying canal over Natural Drains:

• Aqueducts,

• Under Tunnels (UTs),

• Syphons Aqueducts,

• Culverts and Bridges,

• Inlets & Outlets.

(cont…)(cont…)


Definition: Works which are constructed to control and regulate the

discharges, depths, velocities etc, to ensure efficient function of

the Canal system are known as canal regulation works or Cross

Masonry (CM) works.

• Control Structures:

• Head Regulators,

• Cross Regulators,

• Sluices,

• Escapes,

• Canal Falls or drops,,

• Canal Outlets and Modules,

• Silt Ejectors.

(cont…..)(cont…..)


Definition:Definition:

Communication and Service Structures: Communication and Service Structures:

• Culverts and Bridges.Culverts and Bridges.

Flow Measurement Structures or Meters: Flow Measurement Structures or Meters:

• Metering Flumes and Metering Flumes and

• WeirsWeirs

• Drops or falls.Drops or falls.


Definition:

A canal is an artificial channel, trapezoidal in shape

to carry water to the field from a source, such as a

reservoir, river or a tank.

• The motive force in the flow of an open channel is the slope of

the water surface

• The water flows from higher level to lower level by virtue of

gravity.

• The resistance in the canal are surface tension, atmospheric

pressure, surface friction at the bottom and sides.


Canal Alignment:

• The canal has to be aligned in such a way that it

covers the entire area proposed to be irrigated

with the shortest possible length and at the

same time its cost includes the cost of Cross

Drainage and Cross Masonry works and they are

the minimum.

• A shorter length ensures less loss of head due to

friction and smaller loss of discharge due to

seepage and evaporation.

Canals & Design PrinciplesCanals & Design Principles Classification: Canals are classified based on

• Canal excavation in Soils: Alluvial Canals and Non- alluvial Canals

• Functions of the Canal: Irrigation Canal–Carrier Canal Feeder canal – Navigation Canal – Power Canal

• Shape of channel: Circular, Rectangular, Trapezoidal, Triangular, Parabolic

• Canal alignment: Contour Canals - Ridge Canals or water shed canals – Side Slope Canals.

• Discharge and Importance: Main Canal-Branch Canal-Major and Minor Distributaries-Water course.

• Nature of the Canal: Un-lined canal-Lined canal.

Canals & Design PrinciplesCanals & Design Principles Design parameters:

Definitions:• Water requirement of a crop:

• Total quantity of water required from the time of sown to it is harvested.

• Crop Period: • It is the time, in days required for irrigated water from

sowing to last wetting.• Base Period (B):

• The period for which water is supplied in days from ground preparation for planting to the last wetting.

• Duty of water or Duty (D): • It is the irrigation capacity of unit water, expressed in

Hectares per Cumecs (acres per cusec).• Delta Δ :

• It is the total depth of water required to a crop for its full growth may be expressed in hectare-meters (Acre-ft), in million cubic meters (million cubic feet) or simply as depth of water (without percolation or evaporation loses).

Canals & Design PrinciplesCanals & Design Principles Design Parameters:

Duty of water or Duty (D): • It can be expressed as,

1. One cumec of water can irrigate the number of Hectares during base period. i.e. 1700 hectares/cumec (120 acres /cusec)

2. Total depth of water (delta) i.e. 1200mm (4 feet) over a base period.

3. One million cubic meters can irrigate number of Hectares.Being adopted in minor irrigation Tanks (10000 acres per TMC)

4. Hectare meters water can irrigate number of hectares i, being adopted for tanks.

CROPS AND CROP CALANDER:• After deciding the cropping pattern water requirement of each

crop shall be worked out considering the soil conditions and the climatic conditions by a suitable method like modified penman’s method


Definitions: Relation ship between Delta and Duty:

Volume (V) in B days = (60x60x24xB) = 86 400 B Cubic meters or cubic feet

Δ. Depth of water = Volume/Area =86 400/104D = 8.64 B/D in meters or 864 B/D cm. in MKS System or 86 400 B/43 560D= 1.985B/D or Say 2.00 B/D in FPS System

D. Duty = 8.64/Δ in Hectors/ cumecs in MKS System or 1.985B/Δ or say 2 B/Δ in acres / cusec in FPS system

1 Acre = 0.4047 hectare 1 hectare = 104 Sq.m or 2.471 acres.1 c/s = 0.0283 cumecs 1 acre per c/s = 14.3 hectare/cumec1 day = 24x60x60 = 86 400 seconds1 cumec day = 8.64 hectare meters or 86 400 cubic meters1 cusec of water running for a day = 2 acre feet.1 acre ft. = 43 560 cu.ft.


Duty in NSP at head including losses;______________________________________________________________________________Sl. No Irrigated Area in ha. ID in ha/cum Wet in ha/cum ID CUM

Wet in ha/cum ______________________________________________________________________________1. >12 000 850 715

850>4 000 up to 12 000 900 760 925

3. >40 up to 4 000 1000 8001000

4. Up to 40 at pipe outlet 1400 850 1075

______________________________________________________________________________


Value of Delta in India

______________________________________________________________________________

Sl. No Crop Base period in days Delta in field in Hectare/cumec

_____________________________________________________________________________

1. Rice 120 900

2. Wheat 120 1800

3. Sugar cane 360 800

4. Cotton 200 1400

5. Vegetables 120 700

6. Bajri 120 500

7. Ground –nut

8. Chilies

______________________________________________________________________________


Discharge:

The discharge capacity of the canal is the maximum discharge

required for the ayacut for the given duty and the losses in the system.

It shall be fixed based on,

The cultivable command area,

Water allowance, i.e. the outlet capacity in cumecs/s per thousand

hectares considering the duty, intensity, proposed crop ratio, water

availability, etc; and

Transmission losses due to seepage and evaporation from canals

water courses and irrigated area.


Discharge: • The carrying capacities of the canals and distributaries have to be

worked out from head to tail.

• The canal and the distributaries shall be designed not only to carry the supplies at peak demand but also to carry the normal supplies at all times, with water levels sufficient to irrigate the command.

Full Supply Level (FSL): • The levels of water required in a channel are the levels that command

the land in full, or the maximum water level available at the source. • The FSLs shall be decided beginning with out lets, minors,

distributaries, branch canals, and then main canal.• The design of canals and distributaries to be carried out such that the

command of all lands is attained even when half of full supplies are carried.

Canals & Design PrinciplesCanals & Design Principles

Design parameters:

• Best Discharging Channel is that which for the same

Cross Section and slope, passes water with the

maximum velocity and the maximum hydraulic mean

radius (R=A/P), and with the smallest absorption losses

commensurate with economy.

• The canal has to be aligned in such a way that it covers

the entire area proposed to be irrigated with the

shortest possible length and at the same time its cost

includes the cost of Cross Drainage and Cross Masonry

works and they are the minimum.


The common procedure is to determine the Width (W) and Depth (D) of a canal for a given discharge (Q), coefficient of rugosity, side slopes, surface fall or bed gradient, and minimum and maximum velocity. The formula for determine the discharge capacity of the canal.

Discharge (Q) = A (area ) x V ( Velocity) The Cross section of the canal will be in

• Full cutting

• Full banking or

• Partial cutting and Partial banking

Canals & Design PrinciplesCanals & Design Principles Important Guidelines: Alignment:

As for as possible Avoid: • CM &CD works on curves. • Canal Syphons• Flume sections• Inlets and out lets• Skew crossings of Bridges and CM & CD works• Provide bridges at designated roads without foregoing

the available facility. Sluices – Discharge conditions:

• Distributaries to draw Full supply when the parent canal is running at three fourths (3/4th) discharge at the head reach or up to the parent canal decreases to 20% of full discharge at head.

• Distributaries to draw full supply when the parent canal is running at Half supply(1/2) discharge at the tail end reaches, or where the parent canal discharge is reduced to 20% of the full discharge at the head.

Canals & Design PrinciplesCanals & Design Principles Important Guidelines: Alignment:

Recommended Loss of head at structures:

______________________________________________

CM&CD works Head loss in mm

______________________________________________

Cross Regulator 75 to 150

Aqueduct 75 to 150

Canal Syphon 75 to 150

Measuring device 75

Bridges Not permitted

______________________________________________

Canals & Design PrinciplesCanals & Design Principles Important Guidelines: Statements:

HP (Hydraulic Particulars) statements reach wise with discharge calculations.

Design of cross sections reach wise. Reach wise ayacut statement. Statement of Structures with HPs reach wise

• Curves statement• Statement of culverts and Bridges• Statement of Regulators• Statement of OTs• Statement of drops• Statement of canal/surplus escapes• Statement of CD works• Statement of CM works. • Recommended Loss of head at structures:

Canals & Design PrinciplesCanals & Design Principles

Important Guidelines: Plans and Drawings:

• LS (Longitudinal section) together with site plan

with contos showing TBL/FSL/CBL GL, reach wise

CSs, HPs reach wise, TP particulars, command

boundaries survey numbers wise and, Village

wise.

• Design of cross sections reach wise.

• Condensed LS Reach wise.

• Index plan showing the head works and canal

alignment with alternatives studied, and duly

marking the final alignment.

THANK YOUTHANK YOU

training programme on engineering designs-canal structures general design principles canals

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