A History of Water Distribution

8/12/2019 A History of Water Distribution

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A history of water distributionAuthor(s): Thomas M. WalskiSource: Journal (American Water Works Association), Vol. 98, No. 3, 125th Anniversary ofthe American Water Works Association: Standing the Test of Time (March 2006), pp. 110-116,118, 120-121Published by: American Water Works AssociationStable URL: http://www.jstor.org/stable/41314571.

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J rtater

&v&strihution

Thomas M. Walski

^^>day, water utility customers take it forgranted that they canturn on their faucets and that clean water with adequate pressurewill be delivered to them through a water distribution system.Throughout much of human history, however, this conveniencehas not been available. It took a large number of incrementaladvances in science and technology to make modern water distri-bution systems as reliable and inexpensive as they are today.Early history

Early humans had to carry their water from the source to thepoint of consumption. With such an effortrequired, only mini-mal water fordrinking and washing was available. The large vol-umes of water that we use today for showering, toilet flushing,firefighting, nd irrigation could not be delivered manually.

110 MARCH006 JOURNALWWA98:3 WALSKI

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WALSKI98:3 JOURNALWWAMARCH006 111

Crouch1993) reportedhat he arliestpipedwaterupply ated ack otwomillen-niabeforehe ime fChrist. emnantsfpipeswere iscoverednMinoan ities ntheMediterraneansland fCrete,nd thosesystemsupplied aterhroughoughly1400B.C. Some f he ewersnCrete tillfunctionoday.Cities uch sEphesus ndPergenAsiaMinormodern-dayurkey)adfunctioningwaterystemsenturieseforehe ime fChristMays, 000).Most ipes nthosedaysweremade f lay.There rereportsf arlycrew umps,inventedyArchimedesf yracuse, eingused nthe irstentury.C. (Oldfather,1933).Thepumpswere sedforrrigationandfor emovingater romheholds fships butnot or rinkingater).The most xtensive ater istributionys-temsn ncientimes ere heRoman que-ducts, hichonveyed aterong istancesbymeans fgravityhroughcollectionfopen nd losed onduits.hefirstqueductwasbuiltn312B.C.,and everalmorewereadded ver he enturiesSanks, 005).TheRomanslso ntroducedeadpressureipes.The word lumberomes romhe atinword oread, lumbium.Afterhe all f heRoman mpire dur-ing he arkAges the echnologyor eliv-ering atereteriorated,nd anitationbecame oorerhan thadbeen nRomantimesMays, 000). t wasn't ntil fterheRenaissancehat he echnologyodeliverwateregan o volve ncemore.While omplex ater istributionys-tems ere ot ommonnthemiddleges,systemsf hannels ere onstructedomovewaterromhewell ourcesn ndoutof asdes. ome f hese hannels hichwere alled eats'nEnglandre tillnexis-tence oday Robins, 946).Transition to modern times

Inthe 3thentury,5.5-kmeadpipelinewas nstalledntheUnited ingdomo onveywaterromybournerook oLondon. ev-eral imilaripeswere ateronstructed,utservice as nly rovidedo centralointnLondon,ndresidentsad o arry ater otheir omesnbucketsSanks, 005).

Acrudewater heelcalleda forcier)as nstalled ^ W^^SWjSwtheThamesRiver ^topumpwater a ^ t

was drivenby he lowwatertheThames

2005).The record *shows hatwas installedatDillenburgastleGermanyn1455. ron ip-ingwasexpensive.tappears hatthe irst ajor ipeline as 25-kmine romMarly-on-SeinenFrance othe alace fVersailles,hichwascompletedn1664.Early ast-ironipeusedflangedoints,which reno onger sedfor uried ipe(Walskit l,2003).Thebell-and-spigotjointwith ouredeadwas notdevelopeduntil 785 DIPRA, 2003).By hemid-700s,Londonhad more han50km fwatermains hat ad been on-structedut fmixturefwood,cast-iron,nd ead (pipe Sanks, 005). ,, After Most arly ^ *** r small iameter duringate E^n^^es-thetechnoloj^^r pipesweremade f > fardeliveringwat&lfi&ffi&aied,andhad bell-and-

' sattUtiHrniiemmeJ^orertiuispigotointsmade *** beenmRoman times.of ead.For arger >pipes,wood-stavepipe made fnarrowtripsfwood)wasused.Sanks 2005) reportshat ood-stavepipewasused n ome laces hroughheearly 900s.Woodpiperemainstrongslong s t skept ull fwater,nd omewoodpipes re tilln erviceoday.Duringhe1800s, ast-ironipegradu-ally eplaced ooden ipe.The firstast-ironpipeswere aid ntheUnited tatesnPhiladelphia,a., n1817.Wrought-ironpipewas lso used nthe1800s.San Fran-



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IZ


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This ectionofwoodenipeoriginallyariof he eattleWaterDepartment'sdistributionystem,now esidestAWWheadquartersspartof displayfwaterindustryndassociationrtifacts.

AlthoughheDarcy-Weisbachquationcouldbe used odetermineead oss npipes, etermininghe rictionactor asdif-ficult. .S.WilliamsndAllenHazen 1906)developednequation or ead oss nsmoothurbulentlow ith C-factornsteadof he rictionactor.ecause heC- actorssignificandyore onstantndeasier ouse,widespreadse of heHazen-Williamsqua-tion ollowed.ItwastheGerman rocketcientistsnthe arly0th enturyhodevelopedmorehoroughnderstandingf he ela-tionshipsetweenolidbodies ndmovingfluids.udwig randtlndhis ssociatesTheodor onKarmen,ohanNikuradse,Heinrichlasius, ndThomas tantondeterminedhattwas thenature f heboundaryayer etween he luid nd solidphases hat eterminesrag andhead oss).Nikuradseevelopedhe amousxperi-mentsnwhich niformandgrains ereglued othe nsides fpipes nd head osswasthenmeasuredor arious elocities.Theserelationshipsre ummarizedndia-grams y tanton, unter ouse, nd later)LewisMoody; heyhow he elationshipsamongheReynolds umber,iperough-ness, ndfrictionactorWalskit l,2003).Althoughhere as generalwarenessfhydraulicransientsefore897, twas nthat earhat icolai oukowskyirstemon-stratedoth heoreticallyndexperimentallythe coustic ature fwater ammeresultingfromalve losure. e alsopresentednequationhat elated hemagnitudef ran-sient ressureothe hangenvelocity(Rouse& Ince,1980).PipingMost lderwatermainsn North mericaaremade f ast ron. riginally,ast ronwas ast erticallynpits, ut his ype f ronwasreplacedy entrifugallypun ast roninthe 920s.By he 930s, ell-and-spigotpipeointsmade romouredeadwerebeing eplaced ymechanicaloints-andlater y oll-onnd then ush-onoints.Today, wide arietyfoints n ddition opush-onoints savailable,ncludinglanged,ball nd ocket,ndrestrainedoints(DIPRA, 2003).

The firstseof ement-mortariningfpipes ook lace nCharleston,.C., in1922.Tohelppreventnternalorrosion,cement-mortariningf ast-ironipeshadbecome tandardractice y he 940s.Ductile-ironipewasfirstsed n1948,and thas ince eplacedastron nnew nstal-lations. uctile-ironipehasgreaterensilestrengtht essweighthan ast-ironipe.TheCast ron ipeResearch ssociationhangeditsname o he uctileron ipeResearchAssociationn1979 DIPRA,2003).Polyethylenencasementf ron ipeswasfirstevelopedn195 tomitigatehe ffectsfcorrosiveoils nmetalipes. he firsttandardfor olyethylenencasementas pprovedn1972 sAWWA 105 DIPRA,2003).Steel ipecanbe manufacturedndiame-ters angingromess han n nch o everalfeet. teel ipe,which asbeenused incethe 9th entury,anbe butt- r piral-weldedinolder ipe twasriveted).oday,it sprimarilysed n arge ransmissionmains,lthoughsomegalvanized-steel ipings usedin mallerizes.

Concreteylin-derpipehasbeenusedforwater istri-bution ince he1940s.Concreteylinderipewasoriginallyreferredo spretensionedipe,but t snowreferredo s bar-wrappedipe.Thistype fpipehasgenerallyeenusedonly orarge-diameterransmissionains.



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2I1izz01D86OPolyvinylhloridePVC)pipe swidelyusedtodaynnew nstallations.t wasfirstdevelopednGermanynthe1930s, nd twas ntroducedntheUnited tatesnthe1950s.The use ofPVCpipebecamemorewidely ccepteds new tandards ere evel-oped n1972tomake t ompatible ithstandardron ipediameters.WWA tan-dardC-900 for VCpipewas pprovedn1976 Uni-Bell,001).Asbestos-cementAC) pipewaswidelyused nthe 0th entury,speciallyn maller

diameteripes.Because fhealth oncerns(especiallyegardingtsmanufacture),t snotwidely sedcurrently.lthoughsbestosis consideredar-cinogenicf nhaled,ingestionfwaterpassing hroughCpipe s not onsid-ered obe a signifi-canthealth isk(FWR,2002).Serviceineswereonce onstructedflead orcopper. eadis no ongerllowedindrinkingater ipingmaterials,ndmostutilitiesave eplacedheiread erviceines.Currently,erviceines remade f opper rany ne of everallastics.Watermains an osecarryingapacitybecause f n nternaluildup f caleor

tuberculation.arlymethods f ehabilitat-ingpipe nvolvedleaningtwith scraperand thendding cementmortariningothe ipes.Cleaning ipesusing oly-urethanepigs was ntroducedater. ewermethods f ehabilitationnclude lip iningandfold-and-forminingwhichnvolvepulling smaller ipe nside he ldpipe)andpipeburstinginwhich ldpipe s burstand then newpipe spulled hroughheremainingavity).Pumps

Earlywaterystems ere rimarilyrav-ity ed.The earliestumps elied n theprinciplesf nArchimedescrew. umpsnmoremodern ater istributionystemswere enerallyteam-drivenositive-dis-placementumps.Chicagonstalledne of he irstteam-drivenumpingystemsnthemid- 860s.Thepumps edChicago's amous atertower, hichwasconstructedn1869 and sstill tanding.Armstrong,976).Duringhe arly 0th entury,hesepumpswere raduallyeplaced y entrifugalpumps riveny lectric otors. hicagoinstalledts irstlectricentrifugalumpsn1910 Sanks, 005).TheHydraulicnstituteoriginallyormedastheHydraulicocietyn1917)publisheditsfirstet f tandards,rade tandardsfthe umpndustry,n1921.Over heyears,pumps ave ecome mallerndrun thigherpeeds.Themajordvance hat asoccurrednrecentears asbeen he evel-opmentfvariablerequencyrivesocon-trol ump peedmore fficiently.FireprotectionAfire ydrantsthemost isible eaturefmostwater istributionystems.nthe arlydays f irefighting,irefightersould igdown o thewoodenwatermain nddrillhole nthe ipe.Thepipewould illwithwater,nd the irefightersould ump hewater nto he ire. fterhe ire asextin-guished, plugwould e nsertednto hepipe.Thus,the ermireplugs still sed nsome laces odescribe ire ydrants.Some f he arliest ork nthe ydraulicsofnozzles ndfittingsasperformedyJohn

Workersnstallmainin heuburbanouthHills f ittsburgh,Pa., irca he 950s.



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Freemannthe ate 800s Rouse8c nce,1980).The firstutomaticireprinklerseredevelopedyHenry armaleen1874.TheNationalire prinklerssociationorigi-nallyalled heNational utomaticprinklerandFire ontrol ssociation) asformedn1914.The National ire rotectionssocia-tion ublishedts irstire rotectionand-bookn1896 NFPA, 003)Early ydrantsere ustom-madeoreachutility,nd twas not ntilwell nto he20th enturyhat utlet ize ndthreadat-tern ere tandardized.nNorth merica,hydrantsregenerallyocated boveground,butn ome uropean ountries,ydrantscanbebelowgroundndcovered y lid.Before 965,firerotectionystemsntheUnited tateswere valuatedy heNationalBoard f ireUnderwriters.owever,changesnthe nsurancendustryaused heboard obereplacedn1965by heAmeri-can nsurance ssociation.n 1971 nsur-ance ervices fficenc.wasformedndcar-ries n the esponsibilityfwaterystemevaluationorhe ropertynsurancendus-tryntheUnited tates singts ire up-pressionating chedule.MeteringHenri itot evelopedhe irstevice ormeasuringluid elocityn1730. n 1875,HiramMills ecame he irstousethe itotgauge omeasurehe ischargeromfirehydrant.owever,itot auges ouldnot eused nclosed ipesuntil he itometerasdevelopedyJohnndEdward ole n 1895(Walskit l,2003).The firstisplacementeter ormeasur-ing ustomer ateronsumptionsing ecip-rocatingistons asdeveloped yWilliamSewelln1850.The firstommerciallyvail-ablemeters eremade yHenryWorthing-ton-they ere /8-n.metershat eighed7lbs AWWA, 986).J.A.Tildenreceivedhe irstatent ordisc metern1892, nd a conicaldiscmeter as soldbyG.A. Bassettnthat ameyearAWWA, 986).Gearsfor hesemeters eeded o becoveredwith il.Thisinconvenienceas eliminated ith hedevelopmentf hemagneticrivemeternthe ate1950s.

The firsturrent eter asdeveloped yReinhardWoltmannGermanynthe ate1700s.Siemens cHalske egan roductionof he irstlosed-pipeurrent etersn1865. The firstmetershat esembledmodern urbinemeters ere alledtorrent etersndwere irstsed n1895. The firstom-poundmeter,hichcontained low-flowdisplacement eterand high-flowurbinenit, aspatentedyJ.A.Tilden n1903 AWWA, 986).Even hough enturi eters renamedaftern talian cientist romhe arly1800s,the irstractical enturi eter asdeveloped yClemensHerschelnMassa-chusettsnthe ate 1800s.Herschel salso credited ith ranslatingheworks fFrontinus rom atin oEnglishRouse8c nce,1980).Most ustomer etersre otalizingetersanddo not rovidenformationnrate fconsumption.owever,rank rainard



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inventeddevicen1931 that ecorded ate-of-flownformations well s total low.Tanks

Storageanks re notherighlyisiblecomponentfwaterystems.hemajorityfabovegroundanksodayre teel,ndtheearliestanks ere onstructedf ivetedplates. hefirstWWAtandardhatincluded elded anks aspublishedn1935;by he 950s,newerechnologyadreplacedonstructinganks ith ivets(AWWA, 998).Bolted anks ith actorycoatings ave een vailable ince he 970sand re ftensed n ituationshat allforsmalleranks.Elevatedank esign asevolved ver heyears rom ulticolumnesign o pedestaldesign.mprovedoatings,athodic rotec-tion ystems,ndbetternspectionech-niqueshave edtomodern ankoatings ithincreasedife pans.Concretesusedfor ndergroundanksand ome anks tgroundevel. .M.Cromdevelopedhe irstuccessfulrestressedconcreteankn1942.Asteel iaphragm,servings both water arriernd verticalreinforcment,asfirstsed nside oncretetanksn1952;by he1960s, hismethod adbecome ommonracticeACI, 2003).Water quality considerationsThroughout uch f hehistoryfwaterdistribution,twas ssumed hatf hewaterenteringhe ystem asof dequate uality,then hewatermergingromhe apwouldalsobe of cceptableuality. esearch ven-tuallyhowed hat aterualityoulddeteri-oratendistributionystemsecause fcross-connections,he rowthfbiofilms,openwateranks,r the eteriorationfdis-tributionystemomponents.The rules hangedntheUnited tateswith he assage f he afeDrinking aterAct n1974 and ts ubsequentmendmentsin1986 nd 1996. Theprimaryhangebroughtbout y henew awwasthe actthat aterualitytandardsowhad tobemet tthe ap.The new egulationsad n mpactnsuch reas s backflowreventionules,hestabilityfwaternorder opreventead nd

copper ontamination,he emovalf eadfrom aterystems,hemonitoringfdisin-fectantesidualsnddisinfectanty-productformation,ndthe overingr bandoningfoldopen torageanks. espite he,ew egu-lations,erious ontaminationvents avesince ccurredn uchplaces sthe owns fCabool nd GideonnMissouriClarkGrayman,998). naddition,he hreatfintentionalontaminationasbecome nincreasinglymportantonsiderationfterterroristttacksnNewYork ity ndWash-ington, .C., in2001.Hydraulic analysis

Solving or lowsndpressuresn realwater istributionystemnvolvesolvingthousandsf imultaneousonlinearqua-tions. ntil ecentdvancesncomputermodeling ere chieved,uch alculationswerempossible. evertheless,ngineersthroughouthe arly 0th enturyere bletodesign nd nalyzehehydraulicsffunctioningater istributionystemsingcombinationf implifications,ules-of-thumb,ndconservatism.heabilityf ngi-neers oconstructystemsxceeded he ro-fession'sbilityo nalyzehem.Freeman eveloped graphicalmethodfor olving roblems ith arallel ipes nthe ate1 00s,andequivalent ipemethodswere sed todecompose omplex roblemsinthe arly 900s Ramalingamt l,2002).Nevertheless,oopedsystemsequiredtediousterativeystemsndheavy se ofsliderules.Hardy ross 1936)attheUniversityfIllinois eveloped systematicabularrocessfor alculatingystem ydraulics.lthoughthis odifiedhe terativerocedures,he al-culationstillnvolvedxtensivelide ule se.

Camp 1943) summarizedhe tate-of-the-artofmanual ydraulicnalysisor etworksndnoted hat etter ield ataweremorempor-tanthan heoreticalalculations.Thefirstomputerolutions fnetworkproblems ere oneonanalog omputers,with lectricallementseing sed to imu-late ipenetworks.heMcllroy etworkAnalyzer asusedbyutilitiesromhe arly1950sthroughhe arly 970s o imulatewater lowWalskit l,2003).



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11x6|

Digital omputerswere tosolvenetworkrob-lems n the arly1950s.Theearly

modelsWg^^T could nlysolve teady-statehydraulicsroblemsandrequired unch-cardinput n argemainframeomput-ers.The first odelwasdeveloped yL.N.Hoagand G.Weinbergor aloAlto, alif.(Ramalingamt l,2002). By1957, wo on-sultingompanies- ader& AssociatesndBrown nd Caldwell haddevelopedmod-els, ndDaticsCorporation as ellingcommercialrogramEngineeringNews-Record1957).Early ydraulicnalysis ethods erebasedoncomputerizingheHardy-Crossmethod, hereasatermethods ook dvan-

tage f he omputer'sbilityo olvematrixproblems. artinnd Peters1963)devel-opedthe irst atrixolutionmethod. atermodelswere evelopedt uchuniversitiesas theUniversityfKentucky,tah tateUniversity,heUniversityfBritish olum-bia, nd theUniversityfAkron.These modelswere ater xtended ohan-dle more omplex ydraulicsnd ncludedpumps, ontrolvalves,ndextended-periodanalysis. overn-mentgenciesuchas theUS ArmyCorpsofEngineersandtheUS Environ-mental rotectionAgencyUSEPA)alsodeveloped heirwnpipenetworkanalysisoftware.ransientnalysisoftware

developmentollowedpath imilaro thatfor etworknalysismodels.The use ofhydraulicnalysis odelsspreadwith he dvent fdesktopomputers.As argerumbersfnewusers eeded up-port, oftwareevelopmenthiftedoprivatefirmshat ouldprovideechnicalupportandvalue-added eatures.^ Simulationoftwareoulddetermineflows ndpressuresut ouldnotselect ptimal ipesizes.Optimaldesign fwater istributionystemssa mathematicallyifficultroblem,ndhundreds fpapers ndreportsavebeenpreparedhat iscussvariousmethods orsystemptimization.esearchersametogetherocompare ptimization odels ttheBattle f heNetwork odelsheld ttheWater esources lanningndManage-ment ivisionConferenceponsored ytheAmericanociety fCivilEngineersnBuffalo, .Y., n1985 Walski tal,1987).The researchers ere iven water istrib-ution esign roblemnd were sked osolve twith arious ptimizationapproaches. he problems still sed as abenchmarkoday.Waterualitymodeling as ntroducednthe 980s.Akeymeetingn1991, ponsoredbyUSEPA andAWWA, roughtogetherinvestigatorsnwaterualitymodelingndled to USEPA' developmentf distributionwaterualitymodelRossman,000).Recent dvancesnhydraulicnalysishave ocused n thentegrationfmodelingwith eospatialata ources. his hasmadeit essdifficultormodelersocreateextremelyrecise, etailedmodelswithminimumfmanualabor,nd data annowbe sharedasilywith ther artiescross hewater tility.Other computer applications

Although ydraulicnalysisfpipenet-works as the irstse andoneof hemostprevalent)f omputersnwater istribution,numeroustherpplicationsave volvedsince omputersame nto he cene.Supervisoryontrolnd data cquisition(SCADA) systemsave hangedhewayoperatorsnteract ith emote acilities.SCADAsystemsan inkwith rogramma-

Irthemid-930sasystematicabularprocessor alculatingsystemydraulicswas eveloped.Althoughhisodifiedtheterativerocedures,the alculationstillinvolvedxtensiveslide ule se. igitalcomputersereirstused o olvenetworkroblemsin he 960s. he arlymodelsouldnlysolveteady-statehydraulicsroblemsand equiredunchcardnputbehindphoto)n argemain-frameomputers.



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r - 'nitvffffers fa* .'/?

ble ogic ontrollersnd remoteelemetryunits t distantacilitiesomore fficientlyoperateystemsndtodiagnose nd olvedistributionystemroblemseforeheybecome erious. oupledwith dvancesndata-loggingquipment,CADAsystemscan nowprovide peratorsmuch etterpicturefwhatsoccurringntheirystems.Mostutilities adpaper-basedworkorder ystemsnplacebefore omputerscame ntouse,but omputerized orkordermanagement.. .


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Thegrowthf henternetasmade hesharingfwater istributionystemnfor-mationmuch asierwithintilities as wellasamong tilitiesnd theiruppliersndregulators.Future trendsAlthoughhe uturendoubtedlyoldsmanyurprises,ome urrentrendsanbeexpectedo ontinue: a betternderstandingfwaterualitytransformationsnpipes, moremphasisnenergyfficiencysenergyrices ise, incorporationfwaterecurityonsid-erationsnto lldesignndoperationdecisions, betterharingf nformationmongcomputerpplicationssassetmanagementbecomesmorewidelyncorporatednto eci-sion-making, wider se of utomated etereading, increasedpplicationfpoint-of-usetreatmentoovercome aterualityrob-lemsndistributionystems,nd moremphasisnrehabilitationndmaintenancef xisting ater istribution

infrastructureas opposedtonewconstruction)AcknowledgmentThe authorhankshendividuals hoprovided aluablenformationndcom-ments n this aper,ncludingindellOrmsbee, obSanks, ndGeorgeTchobanoglous.ThomasM. Walskis a seniordvisoryrod-uctmanagertBentleyystemsnc.,HaestadSolutionsenter,Brian L,Watertown,T06795; 570) 735-1368; [email protected],nexpertnwateresourcesodeling,aswritteneveralbooksndhaspublished orehan 0peer-reviewedrticles-pproximately0ofwhichhave eenublishednJOURNALWWA. e smemberfAWWAndtheWaternvironmentFederationnd s a Fellow ithinhe mericanSocietyfCivil ngineers.e is aformerditorof he ournalf nvironmentalngineeringandhasbeen amed Diplomatenvironmen-talEngineery he mericancademyf nvi-ronmentalngineers.

Martin,.W. Peters,* 963. heApplicationfNewton'sethodoNetworknalysisy igi-tal omputer,our.nstWaterngrs*7:115.Mays,W000.Wateristributionystemsand-bookMcGraw-Hill,ew ork.NFPA(NatLirerotectionssn.),003. irerotec-tion andbook.FPA,uincy,ass.Oldfather,.H*933. iodorusiculus,ibraryfHistory,ol..Loeb lassicalibrary,arvardUniv.ress,ambridge,ass.Ramalingam,;Lingireddy,;&Ormsbee,E.,2002. istoryfWateristributionetwork

Analysis:ver00 earsf rogress.nvir.Wateresourcesistoryroc, SCE50thAnniversaryonf* ashington,.C.Robins,.W,946. hetoryfWaterupply.Oxford,ondon.Rossman,A* 000. PANETser's anual. SEnvi-ronmentalrotectiongency,incinnati.

Rouse,.& nce,., 980. istoryfHydraulics.owaInst,fHydraulices*owa ity,owa.Sank,R.L.,005.Waterransportection, aterStorage,ransport,ndDistributionY. aka-hasi,ditor).ncyclopediaf ifeupportys-temswww.eolss.net).evelopednderheauspicesf heUNESCO,OLSSublishers,Oxford,.K.Uni-Bell,001. andbookfPVCipe,ni-BellVCPipe ssn.,allas.Walski,.M.t l, 003. dvanced ateristributionModelingndManagement,aestadress,

Waterbury,onn.Walski,.M.t l, 987.he attlef heNetworkModels.our. ateresources,lanningMan-agement,13:2:191.Williams,S.&Hazen,* 906. ydraulicables.John ileySons, ew ork.

Documents

A History of Water Distribution