Canal Regulation Works

Canal Regulation Works:
Canal Fall- Necessity and Location- Types of Falls- Cross Regulator and Distributory Head Regulator- Their Functions, Silt Control Devices, Canal Escapes- Types of Escapes.

1. Canal
Regulation
Works
PREPARED BY
ER SANJEEV SINGH
[email protected]

2. Syllabus
•CanalRegulationWorks:
•CanalFall-NecessityandLocation-Typesof
Falls-CrossRegulatorandDistributoryHead
Regulator-TheirFunctions,SiltControl
Devices,CanalEscapes-TypesofEscapes.

3. What is Canal Fall?
•Whenevertheavailablenaturalgroundslopeis
steepthanthedesignedbedslopeofthe
channel,thedifferenceisadjustedby
constructingvertical‘falls’or‘drops’inthecanal
bedatsuitableintervals,asshowninfigure
below.Suchadropinanaturalcanalbedwill
notbestableand,therefore,inordertoretain
thisdrop,amasonrystructureisconstructed.
SuchastructureiscalledaCanalFallora
Canaldrop.

4. Canal Fall

5. CanalFall
•Irrigationcanalsaredesignedforaprescribedbedslope
sothatvelocitybecomesnonsiltingornonscouring.Butif
thegroundtopographyissuchthatinordertomaintain
thecanaldesignedslope,indefinitefillingfromfalling
groundlevelistobemade.Thisindefinitefillingisavoided
byconstructingahydraulicstructureintheplaceof
suddenbedlevel.Thishydraulicstructureiscalledcanalfall
ordrop.Beyondthecanalfall,canalagainmaintainsits
designedslope.

6. CanalFall
•Thus,acanalfallordropisanirrigationstructure
constructedacrossacanaltolowerdownitsbed
leveltomaintainthedesignedslopewhenthereisa
changeofgroundleveltomaintainthedesigned
slopewhenthereischangeofgroundlevel.This
fallingwateratthefallhassomesurplusenergy.The
fallisconstructedinsuchawaythatitcandestroy
thissurplusenergy.

7. Necessity of CanalFalls
•Whentheslopeofthegroundsuddenlychangesto
steeperslope,thepermissiblebedslopecannotbe
maintained.Itrequiresexcessiveearthworkin
fillingtomaintaintheslope.Insuchacasefallsare
providedtoavoidexcessiveearthworkinfilling

8. Necessity of CanalFalls

9. Necessity of CanalFalls
•Whentheslopeofthegroundismoreorless
uniformandtheslopeisgreaterthanthe
permissiblebedslopeofcanal.

10. Necessity of CanalFalls
•Incross-drainageworks,whenthedifference
betweenbedlevelofcanalandthatof
drainageissmallorwhentheF.S.Lofthe
canalisabovethebedlevelofdrainagethen
thecanalfallisnecessarytocarrythecanal
waterbelowthestreamordrainage.

11. Necessity of CanalFalls

12. Types of CanalFall
•Dependingonthegroundlevelconditionsandshape
ofthefallthevarioustypesoffallare:
OgeeFall
•TheogeefallwasconstructedbySirProbyCautleyon
theGangaCanal.Thistypeoffallhasgradualconvex
andconcavesurfacesi.e.intheogeeform.Thegradual
convexandconcavesurfaceisprovidedwithanaim
toprovidesmoothtransitionandtoreduce
disturbanceandimpact.Ahydraulicjumpisformed
whichdissipatesapartofkineticenergy.Upstream
anddownstreamofthefallisprovidedbyStone
Pitching.

13. OgeeFall

14. Types of CanalFall
SteppedFall
•Itconsistsofaseriesofverticaldropsintheformof
steps.Thisstepsissuitableinplaceswheresloping
groundisverylongandrequirealongglacisto
connectthehigherbedlevelu/swithlowerbedlevel
d/s.itispracticallyamodificationofrapidfall.The
slopingglacisisdividedintoanumberdropstobring
downthecanalbedstepbysteptoprotectthecanal
bedandsidesfromdamagebyerosion.Brickwallsare
providedateachdrop.Thebedofthecanalwithinthe
fallisprotectedbyrubblemasonrywithsurface
finishingbyrichcementmortar.

15. SteppedFall

16. Types of CanalFall
VerticalFall(SardaFall)
•Inthesimpletype,canalu/sbedisonthelevelof
upstreamcurtainwall,canalu/sbedlevelis
belowthecrestofcurtainwall.Inboththecases,
acisternisformedtoactaswatercushion.Floor
ismadeofconcreteu/sandd/ssidestone
pitchingwithcementgroutingisprovided.This
typeoffallisusedinSardaCanalUPand
therefore,itisalsocalledSardaFall.

17. VerticalFall

18. Types of CanalFall
RapidFall
•Whenthenaturalgroundlevelisevenand
rapid,thisrapidfallissuitable.Itconsistsof
longslopingglacis.Curtainwallsare
providedonbothu/sandd/ssides.Rubble
masonrywithcementgroutingisprovided
fromu/scurtainwalltod/scurtainwall.
Masonrysurfaceisfinishedwitharich
cementmortar.

19. RapidFall

20. Types of CanalFall
StraightGlacisFall
•Itconsistsofastraightglacisprovidedwitha
crestwall.Fordissipationofenergyofflowing
water,awatercushionisprovided.Curtain
wallsareprovidedattoeandheel.Stone
pitchingisrequiredatupstreamand
downstreamofthefall.

21. Straight GlacisFall

22. Types of CanalFall
TrapezoidalNotchFall
•ItwasdesignedbyReidin1894.Inthistypea
bodyorfoundationwallacrossthechannel
consistingofseveraltrapezoidalnotchesbetween
sidepierandintermediatepierisconstructed.
Thesillofthenotchesarekeptatupstreambed
levelofthecanal.Thebodywallismadeof
concrete.Animperviousfloorisprovidedto
resistthescouringeffectoffallingwater.
Upstreamanddownstreamsideofthefallis
protectedbystonepitchingfinishedwithcement
grouting

23. Trapezoidal NotchFall

24. Types of CanalFall
WellorCylinderNotchFall
•Inthistype,waterofcanalfromhigherlevel
isthrowninawelloracylinderfromwhere
itescapesfrombottom.Energyisdissipatedin
thewellinturbulence.Theyaresuitablefor
lowdischargesandareeconomicalalso.

25. Types of CanalFall
MontagueTypeFall
•Inthestraightglacistypeprofile,energy
dissipationisnotcomplete.Therefore,
montaguedevelopedthistypeofprofile
whereenergydissipationtakesplace.His
profileisparabolicandisgivenbythe
followingequation,

26. Montague TypeFall

27. Montague TypeFall

28. Types of CanalFall
InglisorBaffleFall
•Hereglacisisstraightandsloping,butbaffle
wallprovidedonthedownstreamfloor
dissipatetheenergy.Mainbodyofglacisis
madeofconcrete.Curtainwallsbothattoe
andheelareprovided.Stonepitchingare
essentialbothatu/sandd/sends

29. Inglis or BaffleFall

30. CanalEscape
•Itisasidechannelconstructedtoremove
surpluswaterfromanirrigationchannel(main
canal,branchcanal,ordistributaryetc.)intoa
naturaldrain.
•Thewaterintheirrigationchannelmaybecome
surplusdueto-
•Mistake
•Difficulty in regulation at thehead
•Excessive rainfall in the upperreaches
•Outletsbeingclosedbycultivatorsastheyfind
the demand of water isover

31. CanalEscape
•Itisthestructurerequiredtodisposeofsurplusor
excesswaterfromcanalfromtimetotime.Thus,a
canalescapeservesassafetyvalveforcanalsystem.It
providesprotectiontothecanalfrompossibledamage
duetoexcesssupplywhichmaybeduetomistakein
releasingwateratheadregulatororheavyrainfall
thatmakessuddenregulardemandofwater.The
excesssupplymakesthecanalbanksvulnerableto
failureduetoovertoppingordangerousleaks.
Therefore,provisionfordisposingthissurpluswater
informofcanalescapesatsuitableintervalsalongthe
canalisessential.Moreoveremptyingcanalforrepair
andmaintenanceandremovalofsedimentdeposited
inthecanalcanalsobeachievedwiththehelpof
canalescapes.

32. Escapes are usually of the following
threetypes.SurplusEscape
•Itisalsocalledregulatortype.Inthistypesill
oftheescapeiskeptatcanalbedlevelandthe
flowiscontrolledbyagate.Thistypeof
escapesarepreferrednow-a-daysasthey
givebettercontrolandcanbeusedfor
employingthecanalformaintenance.

33. SurplusEscape

34. SurplusEscape

35. Escapes are usually of thefollowing
threetypes.TailEscape
•Atailescapeisprovidedatthetailendofthe
canalandisusefulinmaintainingthe
requiredFSLinthetailreachesofthecanal
andhence,theyarecalledtailescape.

36. TailEscape

37. Escapes are usually of the following
threetypes.ScouringEscape
•Thisescapeisconstructedforthepurposeofscouring
ofexcesssiltdepositedintheheadreachesfromtime
totime.Hence,itiscalledscouringescape.Herethe
silloftheregulatoriskeptatabout0.3mbelowthe
canalbedlevelatescapesite.Whendepositedsilttobe
scoured,ahigherdischargethantheFSLisallowedto
enterthecanalfromtheheadworks.Thegateofthe
escapeisraisedsoastoproducescouringvelocity
whichremovethedepositedsilt.ThistypeofEscape
hasbecomeobsoleteassiltejectorprovidedinthe
canalcanproducebetterefficiency.

38. ScouringEscape

39. HeadRegulator
•RegulatorsConstructedattheofftakingpointarecalledhead
regulators.Whenitisconstructedattheheadofmaincanalit
isknownascanalheadregulator.Andwhenitisconstructed
attheheadofdistributary,itiscalleddistributaryhead
regulator.
•Function:
•Tocontroltheentryofwatereitherfromthereservoiror
from the maincanal.
•To control the entry of silt into off taking or maincanal.
•To serve as a meter for measuring discharge ofwater.

40. HeadRegulator
•Construction:Thecomponentsofheadregulator
dependsuponthesizeofcanalandlocationofhead
regulator.Itconsistsofoneormoregatedresearch
openingswithbarrelsrunningthroughthebank.
Forlargecanalsheadregulatorsareflumedto
facilitatethemeasurementofdischarge.

41. HeadRegulator

42. CrossRegulator
•CrossRegulator
•ARegulatorConstructedinthemaincanalorparent
canaldownstreamofanofftakecanaliscalledcross-
regulator.
•Itisgenerallyconstructedatadistanceof9to12km
alongthemaincanaland6to10kmalongbranch
canal.
•Functions:
•(i) To Control the flow of water in canalsystem
•(ii) To feed the off takingCanals
•(iii) To enable closing of the canal breaches on thed/s
•(iv) To provide roadway for vehiculartraffic

43. CrossRegulator

44. CrossRegulator
Construction:ForCrossRegulatorsabutments
withgroovesandpiersareconstructedparallel
totheparentcanal.Thesillofregulationiskept
littlehigherthantheu/sbedlevelofcanal
acrosswhichitisconstructed.Verticalliftgates
arefittedinthegrooves.Thegatescanbe
operatefromtheroad.

45. Canalregulators

46. Canalregulators

47. CrossRegulator

48. HeadRegulator

49. Silt ControlDevices
•ScouringSluicesorUndersluices,siltpocketandsilt
excluders
•Theabovethreecomponentsareemployedforsilt
controlattheheadwork.Dividewallcreatesasilt
pocket.Siltexcluderconsistsofanumberunder
tunnelsrestingonthefloorpocket.Topfloorofthe
tunnelisatthelevelofsilloftheheadregulator.
•Varioustunnelsofdifferentlengthsaremade.The
tunnelneartheheadregulatorisofsamelengthof
headregulatorandsuccessivetunnelstowardsthe
divide wall are short. Velocity near the silt ladenwater
isdisposeddownstreamthroughtunnelsandunder
sluices.

50. Silt ControlDevices
•SiltExcluder:Thesiltexcluderislocatedon
theu/sofdiversionweirandinfrontofthe
headregulator.Theobjectistoremovesilt
thathasenteredinthestillingbasinthrough
scouringsluices.
•SiltEjector:SiltEjectorislocatedinthecanal
takeofffromthediversionweirat6to10km
inthecanalreach.Itejectsthesiltthathas
enteredinthecanal

51. Silt ControlDevices
SiltExcluder

52. Silt ControlDevices
SiltEjector

53. Silt ControlDevices

54. CanalOutlet/modules
•Acanaloutletoramoduleisasmall
structurebuiltattheheadofthewater
coursesoastoconnectitwithaminorora
distributarychannel.
•Itactsasaconnectinglinkbetweenthe
systemmanagerandthefarmers.

55. CanalOutlet/modules

56. Non-ModularModules
•Non-modularmodulesarethosethroughwhichthe
dischargedependsupontheheaddifferencebetween
thedistributaryandthewatercourse.
•Common examplesare:
(i)Opensluice
(ii)Drowned pipeoutlet

57. Types ofOutlet/modules
•Non-modularmodules

58. Semi-Modules or Flexiblemodules
•Duetoconstruction,asuper-criticalvelocityis
ensuredinthethroatandtherebyallowingthe
formationofajumpintheexpandingflume.
•Theformationofhydraulicjumpmakestheoutlet
dischargeindependentofthewaterlevelinwater
course,thusmakingitasemimodule.Semi-modules
orflexiblemodulesarethosethroughwhichthe
dischargeisindependentofthewaterlevelofthe
water course but depends only upon the water levelof
the distributary so long as a minimum working headis
available.
•Examples are pipe outlet, open flume typeetc.

59. Semi-Modules or Flexiblemodules

60. Rigid Modules or ModularOutlets
•Rigidmodulesormodularoutletsarethosethrough
whichdischargeisconstantandfixedwithinlimits,
irrespectiveofthefluctuationsofthewaterlevelsof
eitherthedistributaryorofthewatercourseorboth.
•AnexampleisGibb’smodule:

61. Gibb’sModule