01. Methods of Irrigation.pdf

Methods of Irrigation

1. CE-402 Irrigation Engineering
1
02. Methods of Irrigation
B.Sc. Civil Engineering 8
th
Semester
Muhammad Ajmal (PhD)
Lecturer
Agri. Engg. Deptt.
Surface Irrigation Sprinkler Irrigation Drip Irrigation

2. 2
Irrigation
Flow Irrigation Lift Irrigation
Perennial
Irrigation
Inundation
Irrigation
1.Direct Irrigation (River Canal Irrigation): Diversion Scheme
2.Storage Irrigation (Reservoir Irrigation): Storage Scheme
3.Combined Irrigation: Storage and diversion scheme
Methods of Irrigation

3. ApplicationofwatertocropsmaybeofanyoftheThreebasicmethods
(a)Surfaceirrigation(b)Subsurfaceirrigation(c)Sprinklerirrigation
Thebasicrequirementforadoptionofanymethodare
(i)Uniformdistributionof6-20cmdepthofwaterdependingonthenatureofcrops.
(ii)Economicalconveyancestructure,
(iii)Largedischargeofwatercausingforreductionofconveyancelosses,andlabour
cost.and
(iv)Mechanisedfarmingispossible
SurfaceIrrigationmethodisfurtherbesub-dividedinto:
①Flooding(WildorControlled)
②FurrowMethod
③ContourFarming
MODE/METHODS/TECHNIQUES OF IRRIGATION

4. Controlledfloodingisfurtherbesub-dividedinto:(i)FreeFlooding(ii)ContourLaterals
Flooding(iii)BorderFlooding(iv)ChecksFlooding(v)BasinFlooding(vi)Furrow
Irrigation
FreeFloodingorOrdinaryFlooding:Inthistypeofirrigationditchesareexcavatedin
field,eitheroncontour(knownascontourflooding)orupanddownknownasfreeflooding.
Whenwaterisappliedonfieldwithoutleveesitisknownaswildfloodingorifleveesare
thereitiscontrolledflooding.
BorderFlooding:Inthismethodlandisdividedintoanumberofstrips,separatedbylow
leveescalledborder.Waterisallowtoflowalongthestripsandbepreventedbylevees.
(StandarddimensionsofBorderis100-400moflengthwith10-20mofwidth).After
completionofonestripwatermaybedivertedtoanotherstripandinthiswayirrigationhas
tobecompleted.
SURFACE METHODS OF IRRIGATION

5. ❖ChecksFlooding:Itsimilartofloodingmethodexceptflowiscontrolledbylevees.
Leveescanbeconstructedalongthecontoursoralongtheslopeofafield.Thismethodis
suitableforpermeableaswellaslesspermeablesoil.
❖BasinFlooding:Thismethodiscommonlyusedfortreesorofanytypeofcrops.Inthis
methodabasinwillbeconstructedandwaterwillbeallowedtoirrigatethebasin.This
methodisadoptedtolesspermeablesoil.
❖FurrowIrrigation:Inthismethodacertainpartofthefield(1/5to½)istobeirrigated
whileremainingpartwillbenotirrigated.Thismethodscanbeusedforrowcropswhere
rowtorowspacewillbemore.
❖ZigzagMethod:Inthismethodthelandisdividedintoanumberofsquareorrectangular
plots;eachplotisthensubdividedwiththehelpoflowbundsorlevees.Thismethodis
suitableforrelativelylevelplots.However,itisnotsuitableformodernfarmmachinery
SURFACE METHODS OF IRRIGATION

6. Sprinkler and Drip Methods of Irrigations
SprinklerIrrigation:Atypeofirrigationinwhichwaterissprayedoncropinformof
rainfalldrops.Suchtypeofirrigationcanbeinthefollowingcondition.
❖(i).Thelandcannotbepreparedforsurfacemethods(ii).Slopesareexcessive.(iii).
Topographyisirregular;soiliserosive;depthofsoilisshallowovergravelorsand.
❖Sprinklerirrigationmaybeeitherpermanentsystem;semi-permanentsystemorportable
system.
❖DriportrickleIrrigation:Applicationofwatertotherootsofcropindropformis
knownastrickleirrigation.Waterisconveyedthroughasystemofflexiblepipelines,
operatingatlowpressure,andisappliedtotheplantsthroughdripnozzles.Thismethodis
suitableforanytypesoftreeswherethenumberofplantsareminimum.Asanemitteristo
beinstalledateachapplicationofwaterpoint.Indripirrigationtheremustbeproper
controlofwateruse;weedsandpestcontroletc.

7. Sprinkler Irrigation

8. 8Trickle Irrigation

9. 9
Least Efficient
Most Efficient
Flood Irrigation
Furrow Irrigation
Basin Irrigation
Sprinkler Irrigation
Drip Irrigation
Efficiency of Irrigation Methods

10. Surface Irrigation
10

11. Planning a Water resource Project
Planningawaterresourcemeanshowmuchwaterisneededforanarea,what
mustbethemaximumcapacityofacanalsystem.Thefollowingbasicinformation
essentialtoknowaboutthecapacityofcanalatcertaindurations.
BasicDefinitions:
GrossCommandedArea(GCA)
Thetotalarealyingbetweendrainageboundariesofawatershedwhichcanbe
irrigatedorcommandedbyacanalsystem.
CulturableCommandedArea(CCA):Itistheareawhichisirrigatedtogrow
crops.Itisfurtherclassifiedas:
1.CulturableCultivatedArea:Itistheareaonwhichcropisgrownataparticular
timeorincropseason.
2.CulturableUncultivatedArea:Itisthatareainwhichcropisnotsownina
particularseason.

12. Some Basic Definitions
❖InPakistantherearetwomainseasons;Kharifseason(Summer)starts
from1
st
ApriltoendofSeptember.MaincropsareMaize,Cotton,
Tobaccoetc.Rabiseason(Winter)startedfrom1
st
Octoberandendat
theendofMarch.Themaincropsgrowninsuchseasonarewheat,barley,
potatoesetc.
❖IntensityofirrigationisdefinedasthepercentageofCulturable
commandedareaproposedtobeirrigatedeitheracropseasonorduringa
year.
❖ForexampleifCCAofanirrigationfieldis120hectares,outofwhich90
hectaresofthelandiscultivatedduringKharifseason,theintensityof
irrigationduringKharifseasonwillbe(90/120)*100=75%.The
intensityofirrigationduringRabicropwillbe(60/120)*100=50%.
❖However,theyearlyintensityofirrigationisequaltothesumofthetwo,
i.e.equalto125%.Itmeansyearlyintensityofirrigationis>100%.

13. Some Basic Definitions
❖Dutyrepresentstheirrigationcapacityofaunitofwater.Itistherelation
betweenthevolumeofwaterappliedandtheareaofacropirrigatedduring
theentireperiodofthegrowthofthatcrop.ItisdenotedbyD.Likeifone
cumecofwaterisappliedto100hectaresoffieldthroughoutthebase
periodBdaysthenthedutywillbe100hectares/m3sec-1forBdays.
❖Deltaisthetotaldepthofwaterrequiredbyacropduringtheentireperiod
thecropisinthefieldandisdenotedbythesymbolΔ.
❖CropPeriodisthetimeindays,thatacropstakesfromtheinstantofits
sowingtothatofitsharvesting.
❖BasePeriodforacropreferstothewholeperiodofcultivationfromthe
timewhenirrigationwaterisfirstissuedforpreparationofthegroundfor
plantingthecroptoitslastwaterbeforeharvestingandisdenotedbyB.
❖KorPeriodandKordepth:Cropsneedmaximumwateratthestartof1st
watering.Thedepthofsuchwateriskorwaterandtheno.ofdaystoapply
suchwaterisknownaskorperiod.

14. Relation between Duty and Delta
Letthereisacropofbaseperiod(orkorperiod)Bdays.Letonem3/sec(cumec)ofwater
beappliedtothiscroponthefieldforBdays.
ThevolumeofwaterappliedtothiscropforBdaysare
V = (60x 60 x24x B)m
3
= 86400 B m
3
Asdutyisthenumberofhectarestobeirrigatedbyonecumecofdischargetillthe
maturityofcropsothisquantityofwater(Volume)irrigateDhectares.Then
Depthofwaterapplied=Volume/Area=8.64B/Dmeters.LetthisdepthisΔ.So
Δ= 8.64 x B/D
Example:Waterisreleasedattherateof5cumecsattheheadofacanal.Ifthedutyatthe
fieldis100hectares/cumecandthelossofwaterintransitis30%,findtheareaoftheland
thatcanbeirrigated.
GivenData:Q=5m
3
/sec;D=100hect/cumec;losses=30%;
Required: Areaatfield?
Solution:
Area=Duty/Discharge=duty/Q=[100hectares/(m3/sec)/(5m3/sec)]=500hectaresat
theupstreamofcanal.
Area at the field = (100-30)/(100) * 500 = 350 hectares Answer

15. Irrigation Efficiencies
❖Efficientuseofwaterisessentialforoptimumutilizationofwaterforcrop
production.Varioustypesofefficienciesare
❖WaterConveyanceEfficiency:Itisdefinedastheratioofwaterdivertedfrom
asourcetodelivertoafarm.Suchefficiencyshowthelossesinconveyance
system.
❖Mathematically��=
????????????
??????�
??????100.WhereWfiswaterdeliveredtofarmandWr
isthewatersuppliedordivertedfromasource.
❖WaterApplicationEfficiency:Theratioofthequantityofwaterstoredintothe
rootzoneofthecroptothequantityofwaterdivertedtothefield
❖Mathematically�??????=
??????�
????????????
×100.WhereWsiswaterstoredintherootzone
duringirrigationandWfisthewaterdeliveredtothefieldWf=Ws+Rf+Df
whereRfistherunofffromthefarmandDfisthedeeppercolation.Itanalsobe
writtenas�??????=
????????????−(????????????+�??????)
????????????
×100

16. ❖WaterUseEfficiency:Itisdefinedastheratioofwaterbeneficiallyused
includingleachingrequirementstothequantityofwaterdelivered.
❖Mathematically�??????=
????????????
??????�
??????100.WhereWuiswaterusedbeneficiallyand
Wdisthewaterdelivered.
❖WaterStorageEfficiency:Theratioofthewaterstoredintotherootzone
duringirrigationtothewaterneededintherootzonebeforeirrigation.
❖Mathematically�??????=
??????�
????????????
×100.WhereWsiswaterstoredintherootzone
duringirrigationandWnisthewaterneededintherootzonebeforeirrigation.
❖WaterDistributionEfficiency:Itsevaluatesthedegreetowhichwateris
uniformlydistributedthroughouttherootzone.Themoreuniformlythewater
isdistributed,thebetterwillbethecropresponse.
❖Mathematically��=100[1−??????/�]whereyisthedeviationindepthofwater
storedintherootzoneduringirrigation;
distheaveragedepthofwaterstoredintherootzoneduringirrigation.
Irrigation Efficiencies

17. Determination of Irrigation Requirements of Crops
Inordertodeterminetheirrigationrequirementsofcertaincropsthefollowing
termsareused.
ConsumptiveuseorEvapo-transpiration:Thedepthofwaterconsumedby
evaporationandtranspirationduringcropgrowth,includingwaterconsumed
byaccompanyingweedgrowth.
EffectiveRainfall(Re):Thepartofrainfallduringthegrowingperiodofa
cropthatisavailabletomeettheevapo-transpirationneedofcrop.
ConsumptiveIrrigationRequirements(CIR):Itistheamountofirrigation
waterrequiredinordertomeettheevapotranspirationneedsofthecropduring
itsfullgrowth.Itis,therefore,nothingbuttheconsumptiveuseitself,but
exclusiveofeffectiveprecipitation,storedsoilmoisture,orgroundwater.
Whenthelasttwoareignored,thenwecanwriteCIR=Cu–Re

18. NetIrrigationRequirement(NIR):Itistheamountofirrigationwaterrequiredin
ordertomeettheevapo-transpirationneedofthecropaswellasotherneedssuchas
leaching.ThereforeNIR=Cu–Re+waterlostaspercolationinsatisfyingotherneeds
suchasleaching.
FieldIrrigationRequirement(FIR):Itistheamountofwaterrequiredtomeet‘net
irrigationrequirements’plusthewaterlostinpercolationinthefieldwatercourses,
fieldchannelsandinfieldapplicationsofwater.�????????????=
??????????????????
�??????
GrossIrrigationRequirement(GIR):Itisthesumofwaterrequiredtosatisfythe
fieldirrigationrequirementandthewaterlostasconveyancelossesindistributariesup
tothefield.
�????????????=
�????????????
��
;whereEcistheconveyanceefficiency
TimeFactor:Itistheratioofthenumberofdaysthecanalhasactuallyruntothe
numberofdaysofirrigationPeriod.Likeifthenumberofdaysofirrigationis15and
canalrunfor5days.ThenTimefactor=5/15=0.33
CapacityFactor:itistheratioofactualsupplytofullsupplyofthecanal
Determination of Irrigation Requirements of Crops

19. Water Resources of Pakistan
Thewatersupplyavailabletoagricultureisderivedfromthreemainsources,rainfall
whichoccursdirectlyonthecropareas,surfacewaterfromriversorstorage
reservoirs,andusablegroundwaterfromtheaquifers.
Rainfallisnormallyinadequatetosustainmorethanaverylowlevelofagricultural
production,particularlyinthesemi-aridconditionsofPakistan.
Pakistanhasoneofthelargestirrigationsystemsintheworldcomprisingthreemajor
reservoirswithadesigncapacityofabout20BillionCubicMeters(BCM),23
barrages,headworksandsiphons,45mainirrigationcanalscommandinganareaof
about16.6millionhectares.
Irrigatedagricultureisthebackboneforeconomyofthecountrywhereover93%of
theavailablewaterresourcesareconsumed.
Irrigationisusedon80%ofallarablelandandmeetsalmost90%ofallfoodand
fibersrequirements.
Agricultureisthesinglelargessectorofeconomyaccountingforaboutaquarterof
thecountry’sgrossDomesticProducts(GDP).
Itemploys44%ofthelaborforce,supports75%ofthepopulationandaccountsfor
60%offoreignexchange.

20. Water Resources of Pakistan
Theincreasedpopulation,urbanization,industrializationandagricultural
activitieshoweverwidenedthegapbetweenwaterdemandandsupply.The
watershortfallthatwas11%in2004,isexpectedtoincreaseto31%by2025.
Thepercapitawateravailabilitywhichwasabout5600m3in1947hasnow
reducedtoabout1000m3convertingthecountrytoawaterscarecondition.
Duetopoormaintenanceandoldirrigationsystem,theoverallefficiencyisless
than40%.Outof142BCMofwateravailableatthecanalheadworks,only55
BCMisusedbycrops.Theremaining87BCM(60%)islostduringconveyance
throughcanaldistributaries,minors,watercoursesandinfields.
InPakistanthedevelopmentofrainfedareaiscompletelyignored.Thedry
farmingispracticedonabout12Mhathatis40%oftheCulturableland.Itjust
contributelessthan10%tothetotalproduction.Themainreasonsforthislow
productivityare(i)lowanderraticrainfall(ii)soilerosion(iii)pooruseofland
andwaterresourcesduetosmallandfragmentedlandholdingsand(iv)low
agriculturalinputs.

21. CE 402 Irrigation Engineering
Assignment #1
ProblemNo1
Thegrosscommandareaofanirrigationprojectis1.5lakhhectares,where7,500hectares
areunculturable.Theareaofkharifcropis60,000hectaresandthatofRabicropis40,000
hectares.ThedutyofKharifis3000hectares/cumecandthedutyofRabiis4000
hectares/cumec.Find(a)Thedesigndischargeofchannelassuming10%transmissionloss.
(b)IntensityofirrigationforKharifandRabi.
ProblemNo2
Achannelistobedesignedforirrigating5000hectaresinkharifcropand4000hectaresin
Rabicrop.ThewaterrequirementforkharifandRabiare60cmand25cmrespectively.The
Korperiodforkharifis3weeksandforRabiis4weeks.Determinethedischargeofthe
channelforwhichitistobedesigned.

22. Questions?
10 of 10