Practical Irrigation 400 Bad Request nginx/1.2.9

7/29/2019 Practical Irrigation 400 Bad Request nginx/1.2.9

1/22

PRACTICALRRIGATION.By..OHNSTON,..,and.D.TANNARD,

AssistantsinIrrigationInvestigations,fficeofExperimentStations.INTKODUCTIOX.

Whenafarmerentersanewountiywhererrigationsnecessaryhemustdetermine(1 )howhema}^bestdeliverwatertohisland,and(2)whatcropsareadaptedothesoilandforlocaluses.verj^thingwithhimistentative.nlessheisfortifiedbyanincomeoutsideofthatobtainedromhisfarm,hefirstewyearshehasastruggleforexistence.hatthepioneerisoftenovercomeinthisunequalfightisevidencedbymanydesertedhomesndnfinishedrrigationworks.Owingohisinexperienceinirrigation,hemaylosehisropsb } ^notusinghepropervolumefwaterrbyusingitathewrongtime.Onefailureoftenmeanstheabandonmentofeverythingandaretreattoaregionwhereconditionsseemmorefavorable.nanewcountrywheretherainfallsampleforthegrowthfropseriousobstaclesmustbeovercomebeforereturnsarereceivedforthelaborexpended.If,nadditiontohesedifficulties,watermustebroughttothelandforirrigationanddomesticpurposes,theproblemsbecomemuchmorecomplicated,andorrespondinglygreaterreditsduewhenuccessrewardstheattempt.ToheEasternarmer,hoseultivatedandsreollingndbroken,heproblemofspreadingwateroverthesurfaceofthegroundfromditcheshassomeseriousphases.ftenhetreamassingisfarmisborderedbyteepblufis,anditsfallseldomexceeds3or4 feetpermile.nisudgmentheostfaisingwaterromuchsourceinsufiioientc|uantitiesforrrigationwouldnotbejustifiedytheslightincreaseinyieldsorthesavingofanoccasionalcrop.TheWesternIrrigatorwouldarriveatthesameconclusionifhehadtodealv/ithsimilarconditions.isagriculturallandisnearlyalwayssmooth,andusuallyhasagentleslopewithandowardsomenaturaldrainagechannel,ndwouldearnoropswithoutrrigation.hestreamfromwhichheproposestodraw hissupplyofwaterhasalargefall,othataditchakenromtwithamoderateradeanecede491


2/22

492 YEARBOOKOFTHEDEPAETMENTOFAGRICLTEE.rapidl} ,andhencecoveralargeareainashortdistance.combina-tionofhesefeaturesmakestpossibleorndividualsoonstructirrigationworksonthesmallerstreams.his paperwilldeal withthekindfditch ettlerofimitedmeansouldbuildn egionofabundantwatersupply.SMALL. DITCHESWITH VARYING GRADES AND CROSS-SECTIONAL AREAS.

ThepioneerIrrigatorknewbutlittleregardingthemeasurementofwater,hearryingapacityofditches,orhevolumedemandedbyvariouscrops.heexperienceofthefirstfewyearsoftenconvincedhimthathisditchwastoosmall,andhewascompelledtoenlargeittoprovideanamplesupplyofwater.hevolumeone mancouldhandlehealledan'irrigatinghead."hiswasisirstunitofmeasure-ment,andhisditchcarriedone,wo,orthree irrig^atingheads,accord-ingtohisestimate.rudemeasurements wereafterwardsadoptedtoaidhisudgment.eoundtomparativelyasyomeasurehecross-sectionalareaofastream.isfirstgaugingsweremadeinthismanner,usuallydisregardingthevelocityofthecurrent.xperienceinbuildingditchesaughthiminaewyearshowtoadjustthesizeandgradeofhisditchsoastofurnishanadequatesupplyofwaterfortheareatobeirrigated.omeofheollowingonsiderationshavebeensuggestedbyhisexperience.Manythingsaffecttheeasewithwhichditchescanbebuiltandwaterdistributedromhem.heengthofditchnecessarytocoveranypieceoflanddependsonitsfallcomparedwiththatofthestreamandupontheelevationofthelandtobeirrigated.hesmallerthegradeoftheditchandthegreaterthefallofthetream,otherthingsbeingequal,heshortertheditch.owever,hegradeoftheditchshouldnotbeoolight;therwisetsectionmustbegreatlyncreasedodeliverthedesiredvolumeofwater.hegrademustnot beexcessiveor theincreasedvelocityofthecurrentwillresultintheerosionoftheditchbanks.hereforetherangeofgradewhichaditchmayhaveislimited,anditslengthlargelydependsonthefallofthestream.Onheualityofheoilhroughwhichheditchmustecon-structeddependthepermanencyofitschannel,heateofvelocityatwhichwateranafelybecarried,hecostofirstonstruction,andtheeconomicvalueoftheditchasawatercarrier.sheapnessisarequisitefortheconstructionoftheclassofditchestobedealtwithinthispaper,ockworkorexpensiveflumesandotherstructureswillnotbeconsidered.Inordertomorelearlyshowtheifficultiesobemetandover-come,apracticalcasewillbeconsidered.ssumethatitisdesiredtoirrigateanreaof40acresyingnearacreekurnishingasufficientsupplyofwater;ssume,also,hatthecreekhasafallof0feetpermile,andthatthehighestpointofhelandobeirrigatedis5eet


3/22

PRACTICAL IRRIGATIOlsr. 493abovehebottomofhereekthenearestpoint.twillbeseenthatapointonthecreekthree-quartersofamileaboveisonthesamelevelwithheighestpointofhe40acres.tsvidenthatheheadgateoftheditchmustbeabovethispointifweexpectthewaterofthecreektoflowtothefarm,unless dambebuiltinthecreektoraisethewaterhigherthanitsusuallevel.Itmaybeinteresting,aswella sprofitable,ocompareafewofthe-possiblelinesuponv/hichtheditchmightbebuilt.hatwatertendstoseekitsownlevelsaprinciplethatneedsnodemonstration,anditmightbesupposedthatheleastgradewouldcausethewatertoflowthroughheditch.hilethisstrue,itdoesnotentirelyanswerthepurpose,ortheditchmustnotonlybeoneinwhichwaterwillflow,butitmustallowthewatertounfastnoughodeliverattheplacewhereusedadefinitevolumeinagiventime.Theaccompanyingdiagramfig.4)howstheelationbetweenhegradesofheditchesndhefallfhetream. Theline03repre

oFIG.64.Diagramshowinglengthsofditcheswithdifferentgrades.

sents levelinehroughhebottomofhereekathearmandrunningupstreamromhearm.15is evelinehroughhehighestpointofthefarm.heline6^îshegradeofthetream,20feetpermile.henumbers0 ^1, ,and athebottomofhedia-gramindicatemilesupstreamfromthefarm,andthenumbers15 ^(9,o O ^fO ând60 âtheright,howelevation,nfeet,abovethebottomofhereekathefarm.JBÂ( 7 ,AJ)ândAEareheinesfditchesbuiltongradesofone-half,,0,and15feetpermile,respec-tive3^hedistancesfromthepoint0 totheperpendicularsdroppedfromthepointsj?,^DândE^measuretheapproximateengthsoftheditchesbuiltonhecorrespondinggrades.sabovetated,hegradeofhestreamis0feetpermile.fhegradeofheditchis15eetpermilehewolineswouldapproachachotheratherateof feetpermile,andwouldcomeogethertthepoint^ milesabovehearm.ollowingthelineESothebasefhediagram,itseenhatheengthfheditchis miles. Ifheminimum


4/22

494 YEARBOOK OF THE DEPARTMENT OF AGEICLTUEE.gradesakenatone-halfootpermile,heengthsabouthree-quartersofamile.hecorrespondinglengthsofheditcheshavinggi'adesofand10feetpermileare1and1^miles,espectively.Toillustratehowthelengthofheditchdependsuponheallofthestream,lettheline0-SO representthegradelineof streamhav-ingafallof10feetpermile.Oproducedto30showsthataditchhavingafallof5feetpermileis3mileslong.Thefollowingtablegivesdimensionsofanumberofmallditches,withhecorrespondingvelocitiesanddischargesfordifferentgrades;alsothevolumeofmaterial,ncubicyards,toberemovedpermile:

Velocitiesanddischargesofditcheswithdifferentgrades.Dimensionsofditch. Gradeofditch,6inchespermile. Gradeofditch,1ootpermile. Gradeofditch,2feetpermile. Gradeofditch,3feetpermile.

Topwidth.Bot-tomwidth.Depth.

Areaofcrosssection.Veloc-ity. Dis-charge. Veloc-ity. Dis-charge. Veloc-ity. Dis-charge. Veloc-ity. Dis-charge.

Feet. Feet. Feet. Sq.ft. Feetpersec. Cu.ft.persec. Feetpersec. Cu.ft.persec. Feetpersec. Cu.ft.persec. Feetpersec. Cu.ft.persec.1.5 1 0.5 0.625 0.18 0.10 0.34 0.21 0.50 0.31 0.61 0.383.0 2 1.0 2.5 .35 .86 .48 1.21 .72 1.81 .87 2.274.5 3 1.5 5.625 .46 2.56 .67 3.77 1.00 5.60 1.20 6.726.0 4 2.0 10 .50 5.00 .85 8.50 1.24 12.40 1.49 14.9 7.25 5 2.25 13.78 .67 9.23 .96 13.23 1.38 19.02 1.69 23.298.5 6 2.50 18.12 .74 13.40 1.06 19.20 1.52 27.54 1.87 33.889.75 7 2,75 23.03 .81 18.65 1.15 26.48 1.66 38.23 2.04 46.98

11.0 8 3.0 28.50 .88 25.08 1.26 35.91 1.78 50.73 2.18 62.1312.25 9 3.25 34.53 .93 32.13 1.34 46.27 1.93 66.64 2.36 81.4913.50 10 3.5 41.12 1.00 41.12 1.44 59.21 2.04 83.88 2.50 102.78

Dimensionsofditch. Grade4feet ofditch,permile. Grade5feet ofditch,>ermile. Gradefditch,6feetpermile. Gradeofditch,7feetpermile.TopWidth.

Bot-tomwidth.Depth.Areaofcrosssection.

Veloc-ity. Dis-charge. Veloc-ity.

Feetpersec.

Dis-charge. Veloc-ity. Dis-charge. Veloc-ity. Dis-charge.

Feet. Feet. Feet. Sq.ft. Feetpersec. Cu.ftpersec. Cu.ft.persec. Feetpersec. Cu.ft.persec. Feetpersec. Cu.ft.persec.1.5 1 0.5 0.625 0.71 0.44 0.81 0.51 0.91 0.57 0.96 0.603.0 2 1.0 2.5 1.01 2.53 1.16 2.89 1.29 3.23 1.37 8.424.5 3 1.5 5.625 1.39 7.84 1.59 8.97 1.78 9.97 1.88 10.566.0 4 2.0 10 1.74 17.40 1.99 19.90 2.21 22.10 2.34 23.407.25 5 2.25 13.78 1.96 27.00 2.18 30.04 2.43 33.48 2.63 36.248.5 6 2.50 18.12 2.20 39.86 5.45 44.39 2.68 48.56 2.90 52.549.75 7 2.75 23.03 2.36 54.34 2.63 60.56 2.88 63.20 3.12 71.85

11.0 8 3.0 28.50 2.56 72.95 2.86 81.50 3.13 89.20 3.38 96.3212.2513.50

910

3.253.5

343 23 946 35 105.31 3.34 115.3341.12 2.86 117.18 3.22 132.40


5/22

PRACTICAL IBETGATION. 95Velities-anddischargesofditchesivithdifferentgrades-^Gontimied.

Dimensionsofditch. Gradeofditch,feetpermile. Gradeofditch,feetpermil-e. Gradeofditch,10! feetipermile. VolumeofTopwidth.

Bot-tomwidth.Depth.Areaofcrosssection.Velocity. Dis-charge. Veloc-ity. Dis- charge. Veloc-ity. Dis-charge.

materialoberemovedperimiie.i

Feet Feet. Feet. Sq.ft. Feet2)ersec. 'Ciuft..persec. Feet persec. Cii.ft.j)ersec. Feetpersec. Gu.ft.persec. Cu.ds.1.5 1 0.5 0.625 1.04 0.65 1.09 0.68 1.17 1.04 122 3.0 2 1.0 2.5 L48 3.7 1.55 3.88 :1.66 4.26 4894. ,5 3 1.5 : 5.625: 2.03: 11.42 2.13 11.99 2.28 12.85 1,100G .O 4 2.0 10 2.53 25.30 .2.66 26.60 2.85 28.50, 1,9567.25 5 2.25 13.78 2.81 3 8.72 2.98 41.05 3.13 43.13 2,6958.5 2.-50 18.12 :3.tl0 56.16 .3.28: 59.142 3.46 62.69 S,544 9.75 78910

2.753.03.253.5

23.0328.5034.5341.12

3.33 76.68 -4r504573 1.012.25 6,7528;04 1 3.50

ilncomputing,thevolumeofjmaterialincubicyardspermileoeemovednheonstructionofachditch,tsassumedhathedit-ehesollowthesurfaceoftheground,husmaintainingaconstantdepth.Theditcheswhoseimensionsreivennheaboveablereofsuchizesaswouldordinarilybebuilt.he}^varyfrom1footto10feetinwidthonthebottomlandfrom6inchesto3 4feetindepth.twillbeseenhathevelocityofhewaterdependsargelyuponhecross-sectionalareasoftheditches.hevelocityinthesmallestditch,withgradef6nchespermile,s0.18ofafootersecond,whilethevelocityinthelargestditchiveninthetableforhesamegradeis1footperecond,orboutfivendne^halftimessreat.ycomparinghevelocitiesgivennanyoneolumnofheabletsseenhathewaternhelargestitchasouroiveimeshevelocitythattasnhemallestne.Knowingheuantityofwaterwhichheditchmustcarry,andthepermissiblegrade,thesizecanbedeterminedbyreferencetohetable.Forinstance,1 -ubiceetofwatererecondseliveredya

ditch feetwidenheop, feetwidenheottom,and ootdeep,with radeof feetermile.hetablehowsthatpracti-callythesamevolumeis.carriedbyaditch4ifeetwideontop, feetonthebottom,andlifeetdeep,withagmdeof6inchespermile.tmaybeinstructiveaswellasnterestingtocomparethesetwoditchestodeterminewhichisthemoreeconomicaltoconstructandtouse.Ifbuilttoconveywatertothefarmlocatedasbeforedescribedhelargerditchwouldeabouthree-fourthsofamileongandwouldrequire/theremovalf25cubicj^aixisofarth.hemaller,ditchwouldeabout mileongand89ubicRvsofarthwoulderemovedinitsconstruction,asavinginthevolumeofearthof41percent. Theossesfromeepagendvaporationnhewoitches


6/22

496 YEAEBOOKOFTHEDEPARTMENTOFAGEICLTRE.wouldbeinproportiontothesurfacesexposedothesoilandoheair,andonthisbasisheossnheargerditchwouldbe2.5percentgreaterthanhatnhemaller.hisomparisonhowshatthecostofconstructionofthesmallerditchisless,andthatitisamoreeconomicalwatercarrierthanthelargerone.Inwateringmostropsheexperiencedrrigatorknowshattsmoreconomicalouseaargeeadfwaterhanasmallne.A personcanirrigateagivenareainesshanone-halfheimewith2 cubiceeterecondhatwouldeequiredwith1cubicootpersecond,andtmightbeutterlyimpossibleorrigateheandwithone-halfacubicfootpersecond,orthereasonthathestreamwouldlikelybeabsorbedbythegroundandsinkintohesubsoilnsteadfflowingoverthesurface.Intheirrigationofmostcropsamancanhandle2or2^cubiceetofwaterpersecondwithlittledifficulty.ssumingthat2icubic feetofwaterpersecondisthelargestvolumethatwillberequiredatanyoneime,heroblemsoonstructaditchhatwilldeliverhisamounttotheand.hesizeofheditchandhegradeuponwhichitistobebuiltarequestionswhichshouldbedecidedpproximatelybeforethetriallineisrun.

METHODSOF RUNNING GRADE LINES FOR SMALLDITCHES.Thegradesformanyoftheearlyditcheswereestablishedbyplow-ingafurrowordiggingatrenchfromthecreektothelandtobeirri-gatedandpermittingthewatertoollowashechannelwasopened.If thewaterflowedtoorapidlythefurroAvwasurnedowardhigherground,ndnasehewaterailedoollowherenchowergroundwassought.fterrunninghepreliminaryfurrowtheinaladjustmentnheradewasmadeyplowing econdne,whicheliminatedthedepressionsanddeviationsinthefirst.Thedegreeofaccuracywhichmaybeattainedingradelinesruninthismannervarieswiththecaretakeninrunningthefirstandsecondfurrowsandnestimatinghevelocityofwaterflowingnhem.fthebanksoftheditcharehighenoughtopreventthewaterfromover-flowingthem,timewillusuallyevenupthelittleinequalitiesingrade.Especiallywillthisbetrueofhoseditchesthatcarryanappreciablequantityofilt,whichisdepositedwhereverthecurrentisslow.nthiswaydepressionsareilledupandtheditchismadeevenanduni-form.hislevelingup"processisnotconfinedtotheditchlaidoutanyparticularway,butisconstantlygoingoninallwaterwayswhereinequalitiesofgradeexist.neadvantageconferredbythismethodishatomistakesremadenheocation,hats,hereareostretchesinheditchwherenogradesallowed,nordoeshegraderuninthewrongdirection.hereverwaterflowsinasmallrenchorfurrowitwillflowmorereadilyintheompletedditch.


7/22

PRACTICAL IBRIATION. 497TRIANGLEWITH PLUMB BOB.

Oneofthemostcommonformsofevelingdeviceisthetriangleor''A."thasprobablybeenusedtorunthegradesforagreaternum-berofitcheshananyotherxcepthengineer'slevel.heeasewithwhichtcanbeconstructedandhesimplicityoftsadjustmentandusearethepointsthathaveappealedstrongly tothepioneer ditchbuilder.heusualformsthatofatrianglewhosebaseandongestsideisfrom0to16ifeetinlength.hedifferentlengthswhichmayconvenientlybeusedaregiveninthetablefollowing: Numberoftimestrianglesofdifferentlengthsareusedin1mileandtheamountsvhichshouldbeallowedforvariousgrades.

Lengthofbaseoftriangle.Numberoftimestrianglemustbeappliedinamile.

Amounttobeallowedinthelengthofthetrianglefordifferentgrades.4feetpermile.

5feetpermile.6feetpermile.



Feet.1011 12 15 16 16h

523 480 440352 330320

Inch. Inch.ii

Inch.i

i

Inch.

i

Inch.

i

Inch.4

A

Inch.

Theeadings'4eet,"'5eet,"etc.,overthelastevencolumnsofheaboveablerethenumberfeetofallnheitchesermileoflength;heractionsinheseolumnsgivennchesheall

FIG.65.Trianglewithplumbbob.whichmustbeallowedintheengthofheriangle.heseareor-recttothenearestne-sixteenthofannch,whichisscloseasheinstrumentcanbei^ead.heablehowshatfherianglebe2 feetlongandafallofthree-sixteenthsofaninchbeallowed,thegradeofheditchwillvarybetween5.5and8.5eetpermile.Fig.oshows rianglewithabasef1eet. Itsonstruction


8/22

498 YEAEBOOK OF THEDEPARTMEOT:OF AGEICULTBE.requiresa6-inchboard,AOj1:1eetlong,orhebase;ortheotherlongside,5(7,a-inchboard11 feetlong,andforthe shortside,AB^a-inchboard6ifeetlong.he-tinchboard,.ifii>,alongwhichheplumbineangs,Is eetand nchesong.worhreewidestaplesshouldbedrivenintohisboardoverthelumbinetolimititsswing.heplumbinesofuchengthhathepointfheplumb bob;justlearsthepperdgeofhebase.AC,heplumbbobforthisdevicehouldhavealong,slenderpoint,othatItsposi-tioncanbe moreeasilyseen..markmaybemadeonBJ)justabovetheplumbbobondicateheenteroftsswing.helineishenreadinsteadofhepointofheplunibbob.

Theadjustmentofhetriangleconsistsinlocatingandmarkingtheplacewherethepointof:theboborlinecomeswhenthebaseislevel.Thisisdoneinthefollowingmanirer:Drrve"twostakesintheground,makinghedistance-betweenthemequalothelengthofhebaseoftheriangle.hetakeshouldbedrivenoheiropswillesnearlylevelascanbeestimated.laceherianglewiththeendsofitsbaserestingonthestakes;oldthetriangleinaverticalplaneandnoticefheplumbswingslearofthestaples;ftdoesnot,drivethehigherstakeuntiltdoes.heplumbbobsllowedoettle,andamarkismadeonthebasedirectlyunderit pointorbackofthelinenMD.herianglesheneversedponhetakesndanothermarksmadeonhebaseoronheuprightBD,.perma-nentlineisthendrawnacrossthetopofthebasemidwaybetweenthetwomarksalreadymade.or betweenithose.onD,henthetriangleiseldnsuchapositionthatthepointofheplumbbobortheinecomesoheastmarksmade,hebaseofheriangleslevel.legshownat , ncheslong,maybefastenedotheforwardendofthetriangle.Touseheinstrumentorthelocationofditchline,beginathelowerndofheditchndroceedasollows:Drive taketthetartingpoint,eavingtsop6nchesabxveheurfaceofheground.lacetheend ofheriangleonhisstakeandput ontheground,alonghelineofheproposedditch,andmovetohigherorlowergroundasnecessaryinordertobringthepointoftheplumbboborthelineohemarkthatservesondicatewhenthebaseslevel.wopointsonthesamelevellinearethusfixed.tisdesiredinsteadoindapointnear higherthanhesurfaceofhegroundatAbyanamountequaloheradeofheditchnhatdistance.Shorteningthelegl'-bythisamountandmovingitto higherground,keepingthebaseil7level,hedesiredpoint'isfound.hispoiiitlsmarkedbydrivingastakeintheground,hetopofwhichis InchesSibovethesurface.heproperamounttobecutfromtheleg maybedeterminednhismanner:Divide5,280,thenumiberofeetnamile,by11,thelengthofhebase 7ofhetriangle. Thequotient


9/22

PEACTICAL lERIGATIOK.9980isthenumberoftimesthetrianglemustbeappliedtothegroundinlayingoutamileofditch.ividethenumberofinchesinthefallofheditchpermileby480andtheresultwillbetheamountinfrac-tionalartsofninchbywhichtheegEmustbeshortened.naditchhavingafallof eet,or0nches,permile,hisis0dividedby480,orone-eighthofaninch.Theollowingmethodofunningradeineswithhisevicesprobablymoreommonlymployed:heegEisispensedwith,andafterthepointlocatingthecenterofheswingofheplumbbobhasbeenlocated,apieceofwoodofsuchthicknessa stoallowforthegradeinthelengthofhebasestackedunderoneofheends,asat 7 .heworkofayingoutheineanbegineitherattheheadgateorthearm.f uitableocationorheheadgatesound,tmaybedesirabletocommencethere.nhiscaseastake,havingtstop0or2nchesabovethesurfaceofheground,sdrivenathepointselectedfortheheadgateandtheend ofthetriangleisplaceduponit.heendCisturnednhedirectiontheditchisoberun,andwhentheplumbbobcomestorestatthemarkindicatingthatthebaseisevel, stakesdrivensohattstopsvenwithheowerfaceofhepieceofwoodastenednder,hetopsofhestakeswillhenavehepropergrade,andhetrianglecanbemovedor-wardwiththeendAonthestakejustlocatedandanotherstakedrivenasbefore.hisoperationisrepeateduntiltheentirelineisrun.helinesolocatedneednotfollowthecontourofhecountry,butcanbemadefairlydirect.nowingthatthetopsofthestakesareongrade,thecutatanyplacecaneasilybefound.fhetopofhefirststakeis15inchesabovethegradelineathebottomofheditch,olocatethebottomatanyotherstationtsonlynecessarytomeasuredown15inchesfromthetopofthestakethere.Theplumbobslacedearheearofherame,becausetspositioncanbemoreeasilyseenbyapersonholdinghatnduponastake,andthemotioncommunicatedtoitbythemovementoftheend(7 isless.

TRIANGLE WITHCAPENTE'sLEVEL.Thetrianglesrequentlyusednonnectionwithhearpenter's

level,asshowninfig.^,hisdevicecanbeusednwindyweather,whenitwouldbealmostimpossibleounainewithaplumbbob.Theframemaybemadeoftwo3-inch boards,ABandA( 7 ,about8feetlong,anda2-inchby4-inchpiece,DE^about eetong.hewopieces,ABandAC \arecrossedatAandfastenedwithonenail;maketheengthofABexactlyqualoA( 7 ,ay eet,andmakemarksat and7onheenterinefhepieces.6^isatraightedgeabout12feetlong,usedtemporarilyintheconstructionofheframe.Markupon itsupperedgetwopoints11feetapart.ringthemarksatBandCtohepointsnhetraightedge,whichsemporarily


10/22

500 YEAEBOOK OF THE DEPAETMENT OF AOEICULTUEE.fastenedwithnailsinthisposition.DisnowlaidoffqualtoAE^saybout eet,ndhewopointsDandEmarked.he by4piece,DEîsnowlaidacrossherame,placingtsupperdgeonthepointsDandE,tsoeittedandpermanentlyastenednthisposition.he3-inchboards, ândDC arenextputinplaceandnailedthere.heyholdtheendsofthelegssecurelyinposition.Theamountoffallin11feetisthencalculatedortakenfromthetableonpage497.tsaidffandmarkedonAB^measuringromheupperedgeofBC.hepieceBOisnowloosenedatBandtheupperedgebroughttothismark.helegsofthetrianglearecutalongthestraightedgeofB0,heegABshouldbemarkednomewaytoindicatethatitistobeusedontheupstreamendofthetriangle.

Thismethodofonstructingheevelingevicessumeshathecarpenter'slevelisinadjustment.fteedsadjusting,emovehelevelfromtheframeandproceedasfollows:Drivetwostakes,AandB^nthegrounduntiltheirtopsarenearlyonthesamelevel. Place

FIG.66.Trianglewithcarpenter'slevel.oneend,Aôfthecarpenter'slevelonthestakeAandtheotherend,B,onthestakeB,riveoneofthestakesuntilthebubblecomes tothecenterofthetube.lacethendAofheevelonhestakeBandhendBonhestakeAandnotethepositionofheubble.Reversetheendsoftheleveltotheirformerpositionndeefhebubbleeturnsoheenterofheube;fnot,epeathepera-tion.fthiscannotbebroughtabout,thelevelshouldnot beconsid-eredrustworthy,andhouldotesed.fterindinghathebubblereturnstothecentersatisfactorily,placehendAuponthestakeBndhendBonhetakeAndorrectne-halfftheapparenterrorbythesetscrewwhichfastensthespiritlevelto thewoodofthecarpenter'slevel.eversetheendsofthelevelanddriveoneofthestakesuntilthebubblecomesagaintoheenter.epeatthisoperationuntilthebubbleisinthecenterinbothpositions.helevelistheninadjustment,andthetopsofthestakesareatheameelevation.


11/22

PEACTICAL IRRIGATION. 01Eeplacethecarpenter'slevelontherameandhedeviceseadyforuse.tshouldbetestedeachtimebeforebeingused.hiscanbedonea sfollows:hecarpenter'sevelisinadjustmentandheupperedgeiBC(fig.6 )s straightine.laceheevelonhisineanddrivetwostakes,oneatBandtheotherat^ohatheiropsareevenwiththeupperedgeofBC ^whenthebubbleisinthecenterofthetube.hetopsofthestakesshouldthenbenearlylevel.yreversingthestraightedgeseveraltimestheycanemoreccuratelydriven,ndanyrrorfhearpenter'sevelaneliminated.Whenthetopsofthestakesareonthesameevelreplacethecarpen-ter'slevelontheframeandmakeitslegsthesamelengthbyaddinga

pieceofwoodtotheshorterone,BO.henthelegsreetonthestakesthebubbleshouldcometothecenterofthetubeandshouldnotchangewhentheendsoftheframearereversed.Inuse,wheneverhebubbleisinthecenterofhetube,he\QgBwillstandnthegroundsmuchigherthanheleg aswillivethepropergradetotheditch.heleg^isplacednahub,asmallstakedrivenlushwithhesurfaceofhegroundatthelowerendoftheditchline.point1eetaboveontheditchineisthenfoundwhereBtouchesthesurfaceofhegroundwhenhebubbleisinthecenterofhetube.hispointsalsomarkedyahub.hesetwopointsmarkhegradeineofheditch.heframeshenarriedforward,placingheegouponheastub,andhisoperationsrepeatedtilltheditchlineisentirelylocated.norderthatthehubsmaybeeasilyfound, smalltakeisdrivenbesideeach.SELECTION OF A SITE FORTHE HEADGATE AND THECHOICE OFDITCH

EINES.Fig.7showshearm,hereek,andthegroundoverwhichheditchistobebuilt.heradeassumedorheditchABs feet.permile,orone-fourthheallofhereek.hereforehereekrises,ngoingupstream,ourtimesasmuchastheditchingoingthesamedistance;ence,thelineoftheditchwillgraduallyapproachthecreek.heineandhecreekwillntersectatapointabout mileabovethefarmoraboutone-eighthofamileaboveB,Itrequentlyoccurs,ashownnig .7 ,hathepointwherethepreliminarylineintersectsthecreekisnotasuitableonefortheloca-tionofheheadgate.hebanksofhecreekarehigh,husmakingadeepcutnecessary,andowingoabendntschannelhecurrentishrownowardheppositeideofhetream.foranysuchreasonsheditchannotbeheaplyoronvenientlytakenut,he

banksofthecreekaboveshouldbecarefullyexamined,toseeifthereisnotamoredesirableocation.upposeapoint,B^sfoundboutaquarterofamileabove,wherethebanksarenothighandwhereanoutercurvedirectshecurrentowardheheadgate. Ifhestream


12/22

502 YEAEBOOK O F THE DEPABTMEKT OF AGEICULTUEE.issubjectosuddenandheavyfloods,itmightbebetterforthehead-gatetobelocatedn traightortionfhehannelatherhanuponthecurve.AfterdecidingthattheheadgateshouldbelocatedatD^itisneces-sarytodeterminehowtocarrythewaterfromtheretothefarm.heheadgateDcaneitherbeconnectedwithsomepointofthepreliminaryline,asB^oranewlinecaneruneadingdirectlytohearm,asshownbytheupperdottedlineDA,hereareanumberofquestionstobetakenntoconsiderationeforeachoiceetweenthewoinesshouldbedecidedupon.suallythehigherthe ditchlinetherougherthecountry.ftenrocksencountered,andhepperinesgen-erallymuchmorecrookediftfollowsthesurfaceoftheground. A

;:'-


13/22

EEAOTIC:L lEEIGATION. 503thereforedecidedpon.heallofwateroyerhedropis^feet,thusallowingagi deof feetpermilenthehortditch.fhisprecautionwerenottaken,tschannelwouldbewornawayinashorttime,andthemateriiilthuswashedoutwouldbedepositedinthe lowerditch,fromwhichplaceitwouldhavetoberemoved.hedrop(fig.68)consistsof shortlume,D^with flaringapproachandubmergedplatform,4.hefloor^onthegradeofheditchbelowthedrop,breakstheforceof \ the- fallingwater. Theflaringwingsandsubmerged

FIG.8.Detailsoftimberdropin ditch.platformat?protectheditchathatoint. Thedimensionsarealsoishowninfig.% ,Tomarkthelineofheditchwithafurrowafteritasbeeuiprop-erlylocated,etonemanguidetheteam,walkingetweenheheadsofheorsesndoldingaitnachand,whileanotheroldstheplow.fheurfacefheroundwillermit wagontobedrivenverheine,helowmaybeattachedotherearaxle,thedriverdirectingheeamromheseatofhewagon.he-teamisdrivennuchadirectionastoturnthefurrowtothelowersideoftheditch. Ifhesurfaceofhegroundiscomparativelylevelaereas


14/22

504 YEARBOOKOFTHEDEPARTMENTOFAGRICULTURE.thelineofheditch,tisnotnecessaryoollowhetakesloselyinthebends.heditchwillbebetterforbeingstraightenedalittle,whichmaybeonebyoingbovehestakesthatlocatethebendsnearestthecreekandaittlebelowthetakeshatocatehebendsfarthestaway.fhegroundlopesverymuchacrossheditchlinethetakesmustbeollowedlosely.fterheinesmarked,woorhreeurrowsrelowed,urninghemoheoweride.ditchofhisizemaybeuiltlmostwhollywithanordinaryplow,byoingverheine numberofimes.heoosearthinthebottomofheitchmayberemovedwithaplankcraper,howninfig.9.hetongueshouldbelongenoughtoallowtheteamtoworkbelowthebank. Thescraperisliftedoverthelooseearthastheteam

FIG.9.Plank scraper.backs,andheoadsdraggedoutasheeammovesforward.ditchofheizecontemplatedsatheroomalloadmitofusingtheordinaryscrapertoadvantage.

HEADGATE.Asmallditchofthekinddescribedmightbeusedforyearswithoutaeadgate.twill,however,bemuchbetteroavene,ohewatercanbeshutoffwhenitisnotneededforirrigation.Fig.0howsaommonypeofmallheadgate.tonsistsofabox,orlume, feetong, feetwide,and feetdeep,withagate,7),attheendnearesthecreek.tbothndsheidesflareatanangleofabout30^ .nderthem,14feetbelowthefloorofthestruc-

ture7 ,platformsAndBarebuilt.othofheselatformsrecoveredwithearthtothelevelofthefloor,arthisalsocarefullytampedaroundtheoutsideofheheadgate.


15/22

PEACTICAL lEEIGATION. 505Allrecautionshouldeakenoreventwaterromorking*alongtheoutsideoftheheadgate.hestructurema}^beunderminedinashorttimeifonlyasmallstreamfindsitswaybetweentheplanksandtheearth.heflaringwingsandsubmergedplatformarebuiltto

preventhisaction,andlsoomakehestructureecurencaseofhip;hwater.

FIG.70Detailsofheadgate.LAYING OUT FIELD LATERALS.

TheocationofheateralsurnishesnopportunityforheIrri-gatortoshowhisskill.hilethelandisnew,preadingwateroveritwillbeadifficultmatter.t maybempossibleoroperlylocatethemainateralsatirst,ndupplementalateralsandikesmayhaveoeonstructed.eforeheropsanearvestedhesetemporarychannelsmustbefillednndthegroundleveled.heo-retically,heyshouldbegivensuchagradeaswillresultinamoder-atevelocityforhewater,butnotufficientowashheearthalongtheidesndottomfheitch.nerrigatorfonsiderableexperiencerecommendsthatfieldlateralsshouldhaveafallofatleast10feetpermile.helateralsshouldbelocatednearlyatrightangleswiththedirectionofhegreatestslopeofheland,othatwaterwill1 A19003


16/22

506 YEARBOOK OFHE PEPABTMEHT OF AGRICULTURE.flowfromatherthanalonghem.istakeshavebeenmadeincon-structinghemarallelwithheteepestlope.henhewateristurnedromheseitendsofollowratherhanolowawayfromthem,husaddinggreatlytoheworkofherrigator.fhesur-faceofhegroundisomewhatnevenheroblemofocatingthepermanentlateralsbecomescorrespondinglymoredifficult,oftenren-deringtheseofhengineer'slevelnecessar3^tmaybepossibletocoverallheroundylocatingheateralsalongheridges,orthere maybehighpointsentirelysurroundedbylowerground,makingitnecessarytobuildditchesonartificialidges,ordikes,ocarrythewatertothem. Thenexperiencedrrigatoroftenonsidersthatthe

Fie.71.Platoffarm,showing laterals.groundoccupiedby thelateralsiswasteland,becauseitbearsnocrop.Accordingly,hemakeshemarapart,ohatthewatermustflowalongdistanceooverheurfaceetweennytwo.hissuallyresultsnheverirrigationfhatortionfheropnearhelateralinuse,asthewatermustbekeptflowingthereuntiltheentiresurfacetothenextlateralisirrigated.Itwillusuallypaytodosomeworkinsmoothingoffthelittleirregu-laritiesintheurfaceofhefarm.hismaybedonewithplankscraper,ordrag,afterhegroundhaseenlowed.hedragcutsawaythehigherpointsandleavesthedirtinthehollows.hisprep-arationofheurfaceisquitemportant,asteducesheimeandlaborrequiredinirrigating. Amoreuniformdistributionofwateris


17/22

PEAOT IOAL IRRIGATION. 07alsoobtained,whichncreasestsfficienc3^heoretically,heur-faceofthegroundhouldbealaneurface,withjustslopeenoughtoallowthewater,whendeliyeredatheighestpoint,oflownathin,uniformsheet.

Wewillassumehathearmisplantedosuchcropsa sareordi-narilyfoundnhearidegion,ay0cresflfalfa,0acresfgrain, acresofpotatoes, cresofarden, cresofmallfruits,and5acresoforchard,asshownontheplatofthefarm. (Fig.1 .) Ifitboassumedthattheresafallof feetcrosshefarmfromnorthtosouthand2feetfromeasttowest,hewateranbemadetofloweitherwestorsouthfromanypoint.hegreatestlopeofhelandisalittlesouthofouthwest,andhisshedirectionthewatertakesifeftotself.fheateralsreunouthfromhemainditchtheywillmakenngleofbout70^withhisine.uchanarrangementpermitsthewatertoflowwayfromatherhanlongtheaterals.hemainditchdividesat.,shownnig .1 ;nebranchrunssouthtoi,whileasecondunswestto2>,hemiddleofthenorthlineofthefarm,whereitturnsandfl.owssouthto2.hefieldlateralseceivetheirsupplyofwaterdirectlyfromtheseditches.

METHODSOFAPPLYING WATER TO CROPS.Alfalfaisirrigatedbythemethodknownasflooding,whichmaybedescribedasfollows:Nearlyparallelditches,BO^JEFêtc.,aremade100to150feetapartthroughthefield.nthepresentcasesixditchesaremade,10eetpart,dividingtheieldintosixstrips.sheselateralswillremainaslongastheieldsnalfalfa,wemayputdivi-

sionboxes(seefig.2)atBÊêtc.,whereheateralsretakenfromthemainditch.hiswillavoiduttingthroughtheditchbankandrefillingwithearthwhenthewaterischangedfromonelateraltoanother.hedivisionboxissimplyashortflumeplacedintheditchwithachannelleadingaway,usuallyatightangles.erticalleatsareprovidedforholdingflashboardsinlaceorcheckingthewater.Theseoardsmaybelacedithernheranchorhemainditchasdesired.ThedivisionboxatAfig.1)issetsothewaterwillflowtoB,tthispointthedivisionboxissodjustedhatwaterunsintothelat-eral{BC) andthelowerbankofthelateralisutafewfeetfrom7>.Justbelowthecutaanvasdamshrownacrossheditchtoforcethewateroverthesurfaceoftheround.heanvasdamisapieceofheavycloth,5or6feetlongand3or4feetwide,oneedgeofwhichistackedtoapoleongnoughoestnhebanksa sitisthrownacrosstheditch.heclothrestsgainsthebottomandsidesoftbeditchabovethepole,wheretwoorthreehovelfulsofdirtareplacedtoholditinposition.henthewaterfromlateralBOflowingoverthesurfacereachesthelateralEFêntirelycoveringtheintermediate


18/22

508 YEAEBOOK O F THE DEPAETMEKT OF AGEICULTURE.area,anothercutismadenBC^100to150feetfartherfromB,hecanvasdamisa inusedtocheckhewater,whichsallowedtoflow outasbefore.hisoperationisrepeatedtilltheentiresurfaceofthefirststriphasbeencovered.hedivisionboxatBisthensettoshutthewaterfromthelateralBGandallowittoflow toE^ whereitrunsintotheateralEF^andromtoverheurfaceofhenextstrip.Inthismannerstripafterstripisirrigated,illthentirefieldiscov-ered.hefieldlateralsarenotaslargeasthemainditch,anditmay-beecessaryoividehewateretweenwormorefhem.Assuminghattwillequireaquantityofwaterufficientocoverthefieldtoadepthof6inches,inordertogiveitathoroughirrigation,

^^.

k'\,N--

rk ,


19/22

PEACTICAL IREIGATION.09Theirrigatormusteehathewatereachesthoseplaceswhere,anaccountofeleyationsorobstructions,tdoesjiotrunreadily.Fortheirrigationofthecropsonthesouthhalfofthefarm,furrowirrigationsmployed.heotatoesrelantednowsndre''furrowedout"beforebeingrrigated.hissdonebyunningashovelplowbetweenheow ,makingsmallditches,ntowhichhewateristurnedandallowedolowuntilithasreachedtheotherendofthefield.hewateris "set"onacertainnumberofrows,allovfingonlyasmallstream,tolownach.heurfacesnotlooded,butthewaterisconfinedoheurrowsndpercolateslaterallyintothesoil.hewatersakenutfheermanentateralDMathecornerofthefieldandcarriedalonginatemporaryditchparalleltoit.Afterastrip100to150feetwide,containing40or0rows,hasbeenirrigatedfromthefirstopening,hemainateraliscutfartherdown,andtheprocessisrepeated.hegardenmaybeirrigatedina mannersimilartothatdescribedforthepotatoes.Themallruitsndherchardreropsofmorepermanentcharacter,andwilloccupythesameroundor umberfyears.Forthesereasonsdivisionboxesareplacedinhemainlateralwhereitisdesiredtotakeoutwater.rdinarily,mallruitsareirrigatedbythefurrowmethod.tisthoughtbetterpracticebymanyirriga-torsoallowamalltreamofwaterolowbetweenheowsoraconsiderableimehanoallowaargetreamtounorahortperiod.hisivesmoreopportunityforthewaterosoakntothesoil,eavingitinthesameconditionasdoesaheavyrain.Theorchardisirrigatedeitherbyfloodingoryfurrows.fhetwo,hefurrowsystemisperhapsmoreoftenused.arallelfurrows3o eetapartaremadeandmallstreamsofwaterareallowedtoflowinthemuntilthegroundisthoroughlysaturated.Inomeocalitieshebestesultsareobtainedromheorchardswhentheentiresurfaceofthegroundisflooded.areistaken,how-ever,okeepthewaterawayfromherees,astisfoundhattheythrivebetterwhenthewaterdoesnottouchthem,butpercolatesintothesoilandeachestheoots.henallofhegroundbetweenthetreessmoistenedheootspreaduniformly.hereurrowsareusedorirrigatingorchardsheyareoftenplowedunderafterwaterhasbeenapplied.hegroundstheneveledandhesurfacefinelypulverized.songasheurfaceofhegroundemainsnhisconditionevaporationsgreatlyreduced.hismethodequirescon-siderablework,asthelateralshavetobemadesometimepriortotheirrigationoftheorchard.

Thereare othermethodsforapplyingwatertocrops,butallofthemrequireamorelaboratereparationfheurfaceofheground,andneednotbedescribedhere.Whentsossible,ultivationhouldollowachrrigations


20/22

lO YEARBOOKOFTHEBEPABTMEiTOFAGEICULTURE.soonashegroundsdryenoughobeworked.fllropsouldbecultivatedinthiswaytheamountofwaterwhichwouldhavetobeappliedwouldbegreatlyreduced.hedutyofwatersunifornilysmallforcorn,potatoes,orchards,andothercropswhichcanbeeasilycultivated.fthegroundcannotbecultivatedafterithasbeenirri-gated,thesurfacewilloftenbake.hisisinjurioustosomekindsofplantgrowth,andvaporationsherebygreatlyncreased,makinganotherirrigationnecessarymuchsoonerthanitwouldotherwisebe.

WHEN TO lEEIGATE.Inordertodeterminejustwhencropsneedwaterandwhentoapply

itsothattheywillnotsufferfromdrought,norbeinjuredbytoofre-quentortoogenerousapplications,equires knowledgeandexperi-encehatanegainedonlyypracticendacloseobservationofvariouscropsunderirrigation.tistheexperienceofmanypracticalirrigatorsthat,ifanunlimitedsupplyofwaterisavailable,cropsmorefrequentlysufferromoverirrigationhanfromdrought.tisdiffi-culttodeterminewhenthedevelopmentofthecropisfirstarrestedonaccountofalackofmoistureinthesoil.omexperimentersmain-tainthatthisointcanbemoredefinitelydecidedbyanexaminationofhesoilhanytheppearanceofheplant,asheatterhowsevidenceofhecheckntsgrowthsomedaysafterthasoccurred.Usuallyitshenooateopreventseriousloss,asthecroprarelyrecoversromuchtreatmentandseldomreachesthedevelopmentitwouldhaveattainedifithadbeenirrigatedatthepropertime.Plantswillusuallyindicatebyachangeincolor orbytheirgeneralappearancewhetherheyeedwaterorwhenheyhavebeenver-irrigated.ostieldcropsurnoadarkergreenwheninneedofwater,andheeavesndtemshowatendencytodrooprurl.Thelowereavesassumeapalej^ellow.crispordeadappearanceintheowerleavessneofheestndicationshataplantneedswater.rainwhichhasufferedfromdroughtmaymature,butthestrawwillbemallandhortandheernelswillbehrunkenandinferiorinquality.lfalfaandsimilarcropshavetheappearanceofcuredhay.herefieldcropsareoverirrigatedthecolorofthefoliagebecomesayellowishgreenndtheplantshaveaicklyappearance.Theseindicationsvarywiththequalityofthesoil,othatitisimpos-sibletoaydownixedinilesogovernhenumberorrequencyofirrigations.nlylosebservationor numberfearsnhesamefarmwillenableapersontotellbytheappearanceoftheplantswhethertheyneedwaterornot.Theamountofmoistureinthesoilmaybedeterminedwithsufficientaccuracyfortheneedsoftheplantbyexaminingasampletakenafewinchesromheurfacefheround. Iftclingstogetherwhen


21/22

PEACTICAL lEEIGATIOK. 11moldedinaballandshowsherintofhefingers,hereismoistureenoughpresent.fhearthallsapartwhenhehandspened,irrigationisneeded.sstatedabove,hispointispassedsomeaysbeforetheplantshowsindicationsofsuffering.

COST OF BUILDING ANDMAINTAININGADITCH.Theostf mallystemfrrigationimilarohatlreadydescribedmay properlybeconsideredhere.heditchis1Jmileslong,andthemainlateralsonthefarmareofthesamecross-sectionaldimen-sions,andareive-eighthsofmilelong.helateralsinthealfalfa

andgrainfieldshaveatotal lengthoflimiles,andareslightlysmaller.Ashortcalculationshowsthatnearly1,250cubicyardswillhavetobemovednheonstructionofheseditches.hisvolumet entsperubicardmakesheostfhework62.50.heheadgaterequires3 60feetB.M.of2-inchplanksand2by4inchscantling,atacostof$15to$18erhousand.he3 0divisionoxesremadeof2-inchlumberandrequirenearl}^ 4,000feetB.M.heheadgate,drop,anddivisionoxeswillost,nlace,notarrom125 .hiswillmakeaninvestmentofabout$200inthecompletedditches.Ithasbeendemonstratedbyexperimentthatitrequiresavolumeofwatersufficientocoverheareaoadepthof or3eettomatureordinaryieldrops.asinghealculationnheseigures,ndassumingthatthereisnorainfallduringheirrigationseason,itwillrequireanaggregateoffromsixteentotwenty-fourdaystocompletetheworkofirrigationifheditchdelivers2icubicfeetofw^aterpersecondandtheworkiscarriedondayandnight.ssumethattwentydayssameaneriodorthiswork,thecostofrrigationhereforeapproximates1eracre.incesomecropsrequirehathewaterbewatchedcontinuallyduringirrigation,thecostperacreisincreasedsomewhatowingtothenecessityofemplojdngamantoworkatnight.Theaveragecostprobabtydoesnotexceed1.20peracre.Aftertheirst earhecostofepairswillmountoomethinglike0erentfheriginalutlaynuildingheitch,rabout$20.Thefollowingsummarizestheoriginalcostoftheditchandlateralsandtheyearlyutla}^forrepairsandlabor:

Costofditchandlaterals.Makinglevelandrunningline 12 .00Costofexcavationofditchandlaterals 62.50Costofheadgate,drop,divisionboxes,tc 25.00

Total 99.50


22/22

512 YEARBOOK OF THE DEPAETMENT OF AGEICULTUKE.Yearlycostofirrigationamimaint&iianceofditches.

Laborinirrigating 48.00Repairstoditches 20.00Total 68.00

Intheaboveestimatethelaborhasbeenincludedataveragepricesforsuchwork.fthefarmerhastimetodotheworkhimself,hisonlycashoutlaywillbeforlumber.

Documents

Practical Irrigation 400 Bad Request nginx/1.2.9