Lecturenote Micro hydropower development

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EU DELEGATION TO PAKISTAN

LectureNotesonMHPDevelopment

SRSP2012ByNijazLukovac

V.1.0

June,2012

Funded by

the European Union

Member of the COWIConsortium


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TableofContents:

Coursecurriculum......................................................................................................................................9

Introduction.............................................................................................................................................10

1. Datacollectionandacquisition...................................................................................................11

1.1. Survey.......................................................................................................................................11

1.1.1. Overview..................................................................................................................................11

1.1.2. MultiplefrequencyGPS............................................................................................................12

1.1.3. TraditionalmethodsofquickSurvey.................................................................................12

1.2. Hydrology.................................................................................................................................16

1.2.1. Overview..................................................................................................................................16

1.2.2. Analyses....................................................................................................................................17

a) Availabledischarge.....................................................................................................................17

b) Flooddischarge...........................................................................................................................20

1.2.3. Measurements.........................................................................................................................24

c) Measuringweirs..........................................................................................................................25

d) Stagedischargemethod.............................................................................................................25

e) 'Saltgulp'method.......................................................................................................................26

f) Bucketmethod............................................................................................................................27

g) Floatmethod...............................................................................................................................27

h) Currentmeters............................................................................................................................28

i) Automatedmeasurements.........................................................................................................28

1.3. GeologyandGeomechanics.....................................................................................................29

1.3.1. Overview..................................................................................................................................29

2. Basicsofhydraulics.....................................................................................................................33

2.1. Overview.....................................................................................................................................33

2.2. Pipelines......................................................................................................................................33

2.3. Canals..........................................................................................................................................41

2.4. Tyroleanintake............................................................................................................................43

2.4.1. Intake........................................................................................................................................44

2.4.2. Collectioncanal........................................................................................................................46

2.4.3. Spillwayonthesill(Q1/100)........................................................................................................47


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2.4.4. Stillingbasin(Q1/100).................................................................................................................48

2.4.5. Settlingbasin(Qi).....................................................................................................................50

2.4.1. Siltoutlet(Qout).........................................................................................................................52

2.4.2. Spillwayfromsettlingbasin(Qmax)...........................................................................................54

2.4.3. Dutyflowoutlet(Qmin).............................................................................................................54

3. HydropowerbasicsandHydraulicstructures.............................................................................56

3.1. General........................................................................................................................................56

3.2. History.........................................................................................................................................56

3.3. Advantagesanddisadvantages...................................................................................................56

3.4. StreamorCatchmentDevelopment...........................................................................................57

3.5. CostoftheMHP..........................................................................................................................60

3.6. FromwatertoWatts(again).......................................................................................................60

3.7. Differentsizeshydropowerinstallations....................................................................................63

3.8. Smallhydropower.......................................................................................................................64

3.9. Energyuses.................................................................................................................................64

3.10. Componentsofascheme............................................................................................................65

3.10.1. Weirandintake........................................................................................................................66

a) Sideintakewithoutweir.............................................................................................................68

b) Sideintakewithweir...................................................................................................................68

c) Bottomintake.............................................................................................................................71

3.10.2. Channels...................................................................................................................................72

3.10.3. Settlingbasin/Sandtrap..........................................................................................................73

3.10.4. Spillways...................................................................................................................................75

3.10.5. Forebaytank.............................................................................................................................75

3.10.6. PenstockMaterials...................................................................................................................77

3.10.7. Penstock...................................................................................................................................78

d) Penstockjointing.........................................................................................................................84

e) Buryingorsupportingthepenstock............................................................................................84

f) PenstockAnchorBlocksdimensions...........................................................................................85

g) Waterhammer.............................................................................................................................87

3.10.8. Powerhouse..............................................................................................................................89

4. Equipment...................................................................................................................................94

4.1. Hydromechanicalequipment....................................................................................................94


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4.1.1. Trashracks................................................................................................................................94

4.1.2. Rakes........................................................................................................................................95

4.1.3. StoplogsandGates..................................................................................................................96

4.1.4. Valves.......................................................................................................................................97

4.1.5. Airvents...................................................................................................................................98

4.1.6. Airvessels.................................................................................................................................99

4.2. Electromechanicalequipment.................................................................................................100

4.2.1. TurbineSelection....................................................................................................................100

4.2.2. Turbinediameter....................................................................................................................103

4.2.3. Suctionheadforreactiveturbines.........................................................................................104

4.2.1. Pumpsasturbines..................................................................................................................104

4.3. Electricalequipment.................................................................................................................107

4.3.1. Generators/alternators..........................................................................................................107

4.3.2. TransformersandSwitchgears...............................................................................................108

4.3.3. Automationequipment..........................................................................................................109

4.3.4. Localillumination/lighting....................................................................................................110

4.3.5. AntiThunderGrounding........................................................................................................111

5. DesigntoolsandDrawings........................................................................................................112

5.1. Designtools...............................................................................................................................112

5.2. Designphases............................................................................................................................112

5.3. Drawings....................................................................................................................................113

6. Monitoring................................................................................................................................114

7. Practicalexercise.......................................................................................................................118

8. Trainingevaluation....................................................................................................................119

9. Literature...................................................................................................................................120

Figures:

Figure1UsingGPSinthefield...............................................................................................................12

Figure2Measuringheadinsteps.........................................................................................................14

Figure3Measuringheadinstepsusingspiritlevelmeter....................................................................14

Figure4Measuringheadinstepsusingpocketsightinglevel..............................................................15

Figure5Measuringheadinstepsusingclinometermethod................................................................15

Figure6Hydrologic

cycle.......................................................................................................................16


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Figure7ExampleofqspAC(=Fsl)..........................................................................................................18

Figure8ExampletypicalMHPFDC.......................................................................................................18

Figure9Catchmentareaboundaries....................................................................................................19

Figure10

Catchment

area

boundaries

(3D)..........................................................................................19

Figure11ExampleofMHPcatchmentshownon1:25000...................................................................20

Figure12ExampleofintensitycurvesforvariousreturnperiodsforSarajevo.................................22

Figure13Exampleofafloodhydrograph.............................................................................................24

Figure14Flowmeasurementsusingweir.............................................................................................25

Figure15Flowmeasurementsusingfloat............................................................................................26

Figure16Flowmeasurementsusingdilution........................................................................................27

Figure17Flowmeasurementsusingcurrentmeters............................................................................28

Figure18RiverCATinaction................................................................................................................28

Figure19ExampleoftheuseofGoogleEarthinanalysingthearea....................................................29

Figure20Exampleofthegeologicalprofiletakenfromthegeologicalbasemap1:100000..............30

Figure21Exampleofthegeologicalbasemap1:100000....................................................................30

Figure22Landslides..............................................................................................................................30

Figure23Screes.....................................................................................................................................31

Figure24Slopestabilityresults.............................................................................................................31

Figure253Dsitegeologicalpresentation.............................................................................................32

Figure26n=f(R)relationshipintransitionalflowzone.......................................................................35

Figure27 Typicalcanalsection..............................................................................................................41

Figure28 Typicalcanalsectionwithlateralgroundslope.....................................................................41

Figure29Criticaldepthandflowregimes.............................................................................................42

Figure30Typicalchangesofflowregimes...........................................................................................43

Figure31Tyroleanintake......................................................................................................................44

Figure32Waterprofileontheintake..................................................................................................45

Figure

33

Water

profile

on

the

collection

canal...................................................................................47


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Figure34WaterprofilealongSB..........................................................................................................49

Figure35WaterprofilealongSBanddownstream..............................................................................50

Figure36Tyroleanintake drawing.....................................................................................................55

Figure37

Example

of

stream

power

capacity

calculation.....................................................................59

Figure38Typicalarrangementofmicrohydroscheme........................................................................60

Figure39Flowdurationcurve...............................................................................................................61

Figure40Netheaddurationcurve........................................................................................................62

Figure41Powerdurationcurve............................................................................................................62

Figure42Majorcomponentsofamicrohydroscheme........................................................................65

Figure43Examplesoftemporaryintakes..........................................................................................67

Figure44TheexampleofpermanentMHPconcreteintake.............................................................67

Figure45Uncontrolledintake............................................................................................................68

Figure46Examplesideintake...............................................................................................................69

Figure47Overviewofthesideintake...................................................................................................69

Figure48Exampleofgabionsillintake.................................................................................................70

Figure49Examplesideintake...............................................................................................................71

Figure50ExampleofTyrolean(bottomwithdrawal)intake................................................................72

Figure51Typicalheadracecanalsections............................................................................................73

Figure52Typicalsandtrap/settlingbasin..........................................................................................74

Figure53Typicalsandtrap/settlingbasinelevationsketch...............................................................74

Figure54Exampleofcanalsiltation.....................................................................................................75

Figure55Typicalforebaytankdesigndrawing..................................................................................76

Figure56Typicalforebaytankoverview...............................................................................................76

Figure57Comparisonofpipematerials...............................................................................................78

Figure58Penstockalignmentdesigndrawing...................................................................................79

Figure59PenstockAnchorBlocks(ThrustBlocks)................................................................................79

Figure

60

Penstock

Anchor

Blocks

at

Powerhouse................................................................................80


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Figure61PenstockExpansionJoints.....................................................................................................80

Figure62PenstockSupportsspacing...................................................................................................81

Figure63PenstockAlignmentproblems...............................................................................................81

Figure64

Plastic

pipe

laid

on

ground....................................................................................................81

Figure65Plasticpipeburiedinthetrench............................................................................................82

Figure66Penstockplacements.............................................................................................................83

Figure67Penstockdiameteroptimisation............................................................................................84

Figure68Penstocksupports..................................................................................................................85

Figure69Waterhammerschematicsforsuddenclosure......................................................................88

Figure70ResultofwaterhammercomputationforalongMHPpenstock...........................................88

Figure71ExamplesofsimpleMHPPowerhouses.................................................................................89

Figure72TypicalMHPPowerhouse......................................................................................................89

Figure73FrontfaadeofaMHPPowerhouse......................................................................................90

Figure74MHPPowerhouseTailrace..................................................................................................90

Figure75MHPPowerhouseTailrace..................................................................................................91

Figure76TypicalMHPPowerhousewithimpulseturbine....................................................................91

Figure77TypicalMHPPowerhousewithreactionturbine...................................................................92

Figure78Powerhousefoundationforarrangementwithmechanicalgovernor...................................93

Figure79Powerhouseplandrawing......................................................................................................93

Figure80Trashrack..............................................................................................................................94

Figure81Trashrake..............................................................................................................................95

Figure82Slidegates.............................................................................................................................96

Figure83Slidegate...............................................................................................................................96

Figure84Valves....................................................................................................................................97

Figure85Airvent..................................................................................................................................98

Figure86Airvessel................................................................................................................................99

Figure

87

Typical

turbine

selection

diagram.......................................................................................100


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Figure88Typicalturbinefoundationarrangements...........................................................................101

Figure89Nsvs.Hturbinediagram......................................................................................................101

Figure90Hvs.Nsturbinediagram(loglog).......................................................................................102

Figure91

Other

turbine

application

charts.........................................................................................102

Figure92Typicalturbineefficiencycurves..........................................................................................103

Figure93Centrifugalpumpinturbinemode......................................................................................105

Figure94Pumpasturbine..................................................................................................................105

Figure95T15crossflowturbine parts..............................................................................................106

Figure96T15crossflowturbine principle........................................................................................106

Figure97Generators...........................................................................................................................107

Figure98Transformersandswitchgears............................................................................................108

Figure99AutomatedcontrolofMHP.................................................................................................109

Figure100ExampleofGridconnection,electricaldistributionandsupervisionarchitectureofamicro

hydropowerplant..................................................................................................................................110

Figure101Powerhouselighting..........................................................................................................110

Figure102

Powerhouse

grounding.....................................................................................................111

Tables:

Table1SCScurvenumbers....................................................................................................................22

Table2Piperoughness..........................................................................................................................35

Table3Importantpipematerialproperties..........................................................................................36

Table4Canalflowcalculationsparameters.........................................................................................41

Table5ExampleofthecalculationforTyroleanintake........................................................................45

Table6Settlingvelocityoftheparticledependentonwatertemperature/viscosity...........................51

Table7ExampleofPowercomputationforarunofriverMHP...........................................................63

Table8ExampleofHydropowerclassification......................................................................................63

Table9Typicalenergyuses...................................................................................................................64

Table10Comparisonpenstockmaterials.............................................................................................77

Table11Weightcomparisonbythetypeofpipe(diameter500mm,by1m)......................................78


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Coursecurriculum1. Datacollectionandacquisition

1.1. Basicgeodeticsurveyingrequirements.(Couldusehelphere)1.2. Basichydrologicaldatacollectionandanalysis(measurements,historical/witnessdata,

rainfallrunoffanalysesaveragedischarge,minimumandmaximumflowrates,flow

ratingcurve,flowdurationcurve.

1.3. Geologic/geomechanicprospection.

2. Basicsofhydraulics, conveyance systems (steady canalandpipe flow computation), friction

losses,spillwaysandoutlets,introductiontounsteadyflowandtransients/waterhammer.

3. Hydropowerbasics(withemphasisonmicrohydro),determinationofthewatercoursestream

potential (capacity), site selection, site development,possible schemes,design optimisation

and alternative arrangements, equipment selection, calculation of the main power

parameters.Differencesindemanddrivenandpowerdrivenapproachtohydropower.

4. HydraulicstructuresdescriptionofthemainhydraulicstructuresusedinMHPdevelopment:

river diversion (sill, weir), intake, sandtrap/settling basin, headrace (power canal or pipe),

penstock (and its supports and anchors),powerhouse, tailrace (canal)note:Merged with

Hydropower.

5. Hydromechanical equipment: gates, valves, trashracks, rakes, steel pipes (Pending

appropriateexpertise)

6. Electromechanical equipment: Turbine, generator (partly covered but still pending

appropriateexpertise)

7. Electrical equipment: transformers, alternators, switchgears, cabling (Pending

appropriate

expertise)

8. DrawingsTheminimumfortechnicaldrawingsanddetailsforeachMHP

9. MonitoringinstructiontocollectdatafornecessaryMonitoringoftheprogress.

10. Practicalexercise(s)

11. TrainingEvaluation


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IntroductionThenorthwestpartofPakistan(KPK)isveryrichinhydropowerpotential,butitalsohassomeremote

areas with many villages that do not have access to electricity. In principle, these are areas with

considerabledegreeofpoverty.Withtheobjectivetoalleviatethepovertyandtohelpdevelopment

ofthoseareas,EUDhasdecidedtograntfundsfor(amongotherthings)developmentofanumberof

MHPsinthevillagesof7districtsoftheMalakandregion.

PeshawarseatedNGOSarhadRuralSupportProgrammeSRSP,hassubmittedtheProjectProposal

titledProgrammeforEconomicAdvancementandCommunityEmpowerment(PEACE).Alargepart

ofit,nearly50%isdealingwiththesetupandimplementationof297MHPschemesintheregionover

aperiodoffouryears.

Under the title:TechnicalAppraisalandMonitoringofaMicroHydelProgramme inPakistan,EUDissued the ToR for an FWC assignment for a consultantwhowouldprovide technical assistance in

relation to thesaidProposalandProject implementationwithin the first year.TheFWCassignment

envisaged3visitstoPakistanindifferentphasesoftheProposal/Projectdevelopment.TheConsultant

fortheFWCassignment isNijazLukovac(infarthertext:theConsultant),whomadethefirstvisitto

Pakistan(IslamabadandPeshawar)from1st27

thApril2012andpreparedtheReportforPhaseI.

Meanwhile,basedonfindingsofthevisitanddiscussionswithEUD,thedecisionwasmadetoslightly

adjusttheoriginalplanning inawaythat insteadof3thereshouldbe4visitsoftheConsultant,and

thatpartofthesecondvisitwouldbeusedtocarryonaTrainingcourseforSRSPengineers.Thetiming

oftheTrainingisoptimalatthebeginningoftheProjectimplementationphase.

TheConsultanthasproposedaCoursecurriculum (Chapter0),andhasenvisaged theTrainingasan

interactiveworkshop(s)withparticipationofcertainexternalinstructorsaswellasownSRSPsstaff.A

partofthetrainingworkshopwouldalsobeledbytheConsultant.Inordertohavemajorlinesalong

whichthetrainingshouldgo,thedraftofthecoursematerialhasbeenpreparedandpresentedfurther

on. There will be a number of handouts and free software packages distributed as well. The

workshopsaremeanttohaveadegreeofflexibilityandshouldadjust inaccordancewithneedsand

capabilitiesof theparticipants.At theendof theworkshop,aneffortwouldbemade toturn this

materialintoabaseforfutureSRSPMHPmanual.


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1. Datacollectionandacquisition1.1. Survey

1.1.1. Overview

Whatisimportant?

1. Essential:

a. Determiningtheavailablehead

b. Determininglocationsofmajorstructures(intake,sandtrap,headracecanal,forebay,

penstock,powerhouse,tailrace)

c. Baseforpowercalculationsandcostestimate

2. Wouldbebeneficial:

a. Surveyinglocalmapsatstructures

b. longitudinalprofile

c. characteristiccrosssections

EssentialpartwouldbenecessaryforALLMHPsandtherestshouldberequiredatleastforMHPswith

P>100kW.

Each(future)MHPsiteshouldbesurveyedtoadegreethatwouldbesufficienttoprovidebasicdataandparametersforthedesign.Minimallyitshouldinclude:

Locationanddimensionsofmainstructures:o Intake

o Sandtrap(ifany)

o Canal(ifany)

o Forebay

o Powerhouse

Availablegrosshead

Moredetailedsurveydatashouldalsoprovide(ifpossible):

Moredetailedmapsaroundthestructures

Longitudinalprofile

Severalcrosssections

Thosedatawouldprovideabaseforbetterdesignoptimisationandmoreaccuratecostestimate(bill

ofquantities).

Finally, once implemented scheme should ideally be recorded and filed in terms of the Asbuilt

documentation. In other words, once completed, the MHP scheme should be surveyed at actual

locationsofbuiltstructures.


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1.1.2. MultiplefrequencyGPS

InSRSPsProject,ithasbeenforeseentoacquireacoupleofdouble/triplefrequencyGPSSystemsthat

canprovidequickandaccuratedatawhichcaneasilybeimportedintothesoftwareapplicationsused

fordesign(e.g.AutoCAD).Thiskindofprocedureshouldcertainlybeemployedat leastwithlarger

MHPs(say>100kW).DuetothelargenumberoftheMHPstobeconstructedwithin4yearsitmaybe

impossibletousethissophisticatedsurveyingequipmentateachandeverysite.Forveryremotesites

andverysmallMHPsitwouldstillbeacceptabletousemoretraditionalsitemethodsofmeasuring.

Figure1UsingGPSinthefield

1.1.3. TraditionalmethodsofquickSurvey

Severalmethodsexistformeasurementoftheavailablehead.Somemeasurementmethodsaremore

suitableon lowheadsites,butaretootediousand inaccurateonhighheads.Ifpossible,it iswiseto

takeseveralseparatemeasurementsoftheheadateachsite.Advice:Alwaysplanforenoughtimeto

allowonsitecomparisonofsurveyresults.Itisbestnottoleavethesitebeforeanalysingtheresults,

asanypossiblemistakeswillbeeasiertocheckonsite.

Afurtherveryimportantfactortobeawareofisthatthegrossheadisnotstrictlyaconstantbutvaries

withtheriverflow.Astheriverfillsup,thetailwaterleveloftenrisesfasterthantheheadwaterlevel,

thusreducingthetotalheadavailable.

Althoughthisheadvariationismuchlessthanthevariationinflow,itcansignificantlyaffectthepower

available,especially in lowheadschemeswhereeveryhalfmetre isessential.Toassesstheavailable

grossheadaccuratelyheadwaterandtailwaterlevelsneedtobemeasuredforthefullrangeofriver

flows.(SomeexamplesareillustratedinFigure2throughFigure5).

DumpylevelsandtheodoliteTheuseofadumpylevel(orbuilder'slevel)istheconventionalmethodformeasuringheadandshould

be used wherever time and funds allow. Such equipment should be used by experienced operators

whoarecapableofcheckingthecalibrationofthedevice.


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Dumpy levelsareusedwith staffs tomeasurehead ina seriesof stages.Adumpy level isadevice

whichallowstheoperatortotakesightonastaffheldbyacolleague,knowingthatthelineofsightis

exactlyhorizontal.Stagesareusuallylimitedbythelengthofthestafftoaheightchangeofnomore

than3m.Aclearunobstructedviewisneeded,sowoodedsitescanbefrustratedwiththismethod.

Dumpy levelsonly allow ahorizontal sightbut theodolite can alsomeasure vertical andhorizontalangles,givinggreaterversatilityandallowingfasterwork.

Sightingmeters

Handheldsightingmetersmeasuresangleofinclinationofaslope(theyareoftencalledinclinometers

orAbneylevels).

Theycanbeaccurate ifusedbyanexperiencedperson,but it iseasy tomakemistakesanddouble

checking is recommended.Theyaresmallandcompact,andsometimes include range finderswhich

savethetroubleofmeasuring lineardistance.Theerrorwilldependontheskilloftheuserandwilltypicallybebetween2and10%.

Waterfilledtubeandpressuregauge

Itisprobablythebestofthesimplemethodsavailable,butitdoeshaveitspitfalls.Thetwosourcesor

errorwhichmustbeavoidedareoutofcalibrationgaugesandairbubbles inthehose.Toavoidthe

firsterror,youshouldrecalibratethegaugebothbeforeandaftereachmajorsitesurvey.Toavoidthe

second,youshoulduseaclearplastictubeallowingyoutoseebubbles.

Thismethodcanbeusedonhighheadsaswellaslowones,butthechoiceofpressuregaugedepends

ontheheadtobemeasured.

Waterfilledtubeandrod

Thismethod is recommended for lowhead sites. It is cheap, reasonablyaccurateandnotprone to

errors. Inthiscase, ifmorebubblesaretrapped inonerisingsectionofthetubesthan intheother,

thenthedifferenceinverticalheightofthesetsofbubbleswillcauseanequaldifferenceinthehead

beingmeasured,thoughthisisusuallyinsignificant.Twoorthreeseparateattemptsmustbemadeto

ensurethatyourfinalresultsareconsistentandreliable.Inadditiontheresultscanbecrosschecked

againstmeasurementsmadebyanothermethod,forinstancebywaterfilledhoseandpressuregauge.

Spiritlevelandplank

Thismethod is identical inprincipletothewaterfilledtubeandrodmethod.Thedifference isthata

horizontal sighting is established not by water levels but by a carpenter's spirit level placed on a

reliablystraightplankofwoodasdescribedabove.Ongentleslopesthemethod isveryslow,buton

steepslopes it isuseful.Markoneendofplankandturn itateachreadingtocanceltheerrors.The

errorisaround2%.


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MapsLargescalemapsareveryusefulforapproximateheadvalues,butarenotalwaysavailableortotally

reliable.Forhighheadsites(>100m)1:50,000mapsbecomeusefulandarealmostalwaysavailable.

AltimetersThese can be useful for highhead prefeasibility studies. Surveying altimeters in experienced hands

will give errors of as little as 3% in 100 m. Atmospheric pressure variations need to be allowed for,

however,andthismethodcannotbegenerallyrecommendedexceptforapproximatereadings.

Figure2Measuringheadinsteps

Figure3Measuringheadinstepsusingspiritlevelmeter


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Figure4Measuringheadinstepsusingpocketsightinglevel

Figure5Measuringheadinstepsusingclinometermethod

Awaterfilledhosewithpressuregauge(manometer)canalsobelowereddowntofindoutthehead

difference,assaidabove.


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1.2. Hydrology

Figure6Hydrologic

cycle

1.2.1. Overview

Whatisimportant?

1. Essential:

a. Determiningthemeanflowrate(discharge)=availablewaterwhichisarowmaterialfor

Hydropowergeneration.

b. Estimatingflooddischargeinordertosafelyplacerequiredstructures

c. Baseforpowercalculationsandcostestimate


a. Establishingwatergaugingstation(s)

b. Determiningflowratingcurve(s)(FRC)

c. Determiningflowdurationcurve(FDC)

d. Determiningafloodhydrograph

e. Determiningthedutyflowandpoweravailableflow


P>100kW.


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Basichydrologicaldatacollectionandanalysisincludemeasurements,historical/witnessdata,rainfall

runoff analyses average discharge, minimum and maximum flow rates, flow rating curve, flow

durationcurve.

Normally, fora reliableHydrological studybasedonproper statisticalanalyses,onehas tocollect

longtermdata series (20,30,40,50ormoreyears).However,MHP sitesarealmostalways in theunexploredareas,andsome tradeoffsshouldbemade,keeping inmind that themarginoferror

mightbehigh.

ThemajorhydrologicalparametersneededforMHPinstallationinclude:

Meanflowestimation(QAV)

TimedistributionofflowsFlowDurationCurve(FDC)

DepthflowrelationshipFlowRatingCurve(FRC)

Floodwaterdischargesayhundredyearflood(Q1/100)

Floodhydrograph(e.g.SCSUnithydrograph)

1.2.2. Analyses

a) Availabledischarge

Mean flow canbeobtained fromdata series,but since theyarenormallynotavailable, itcouldbe

estimatedbasedonprecipitationdata (whicharemore readilyavailable) combinedwith catchment

characteristicsandgeometry.

Dependingonthecatchmentarea(AC),forgivenannualprecipitation(p),volumeofwaterthatfallson

it,canbecalculatedas:

V=pAC(m3)

Allunitsshouldbeconvertedtom.Precipitation isusuallyexpressed inmillimetreswhileCatchment

areaisexpressedinkm2,orsometimesinhectares(ha)oracres(a).

Ifall thewater could find itsway to the streamandbedrained through it, then the flow couldbe

calculated as ratio of the volume over the time in which that volume was discharged (annually it

meansca.T=31.5106seconds).However,duetoevapotranspiration,aportionofthefallenwater

neverendsup in the stream.The ratioofvolumeofwater that flows through the streamover the

volumeofwaterbroughtbyprecipitationiscommonlycalledrunoffcoefficient.Itisdimensionlessand

commonlymarkedas .Thus,averageflowcanroughlybeestimatedas:

QAV= V/T(m3/s)

Runoffcoefficientdependsontheshapeandslopeofthecatchment,typeofsoilandbedrock,extents

andtypeofvegetationandotherfactors. Itcanrange from0.2to0.8,butmorecommonlytheyfall

withinrangeof0.4to0.6.Ifonewantstobeonthesafetyside,thelowervaluesshouldbeadopted.

If the largercatchment is relativelyknown, thenby itsanalysisaspecificdischargeqSP (l/s/km2)

couldbedeterminedandbasedonit,theactualflowcouldbeestimated.Itusuallyhasaform:

qsp = a AC+ b (l/s/km2)


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Withreciprocaltrendvs.Area:

Figure7Exampleofqsp AC (=Fsl)

TodetermineratedMHPflow,amoredetailedanalysisisneeded.FDCwillgivetheinsightinhowthe

availablevaryingflowscouldbestbeutilised.ForthatonewouldneedatleastonereliableFDCinthe

same or nearby catchment and to make a series of simultaneous flow measurements in order to

determine correlation relationship. In addition, to be able to use longer series from the correlating

gauging station, one would need to form one on the profile of interest (intake) and to make FRC in

ordertobeabletoconvertwaterstagesintoflows.

TypicallyratedflowoftherunofriverMHPisaroundthemeanflow.Therewillbesomefloodwater

during the year (all exceeding Qi) that would spill unutilised, and there should be some duty flow

releasedtosustainlifeinthestreambetweentheintakeandthepowerhouse.Allthisleadstocertain

lossof water for power generation. Typically the ratioof useful mean flow to available flow is 50

60%.

Figure8ExampletypicalMHPFDC

y =-0.0046x +13.515

R2

=0.6196

10.5

11

11.5

12

12.5

13

13.5

0 100 200 300 400 500 600

qsp (l/s/km 2)

Fsl

(km

2)


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Figure9Catchmentareaboundaries

Inordertocarryonabovementionedanalysesoneshoulddeterminethecatchmentareafirst.Forthat

somesortofmapshouldbeavailable.Forsmallcatchmentsideallyitwouldbe1:25000or1:50000or

similar.

Figure10Catchmentareaboundaries(3D)


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Figure11ExampleofMHPcatchmentshownon1:25000

b) Flooddischarge

Remember:Thebiggestenemyofallhydraulicstructuresiswateritselfthroughitsdestructiveforces

offloodorleakage. ofallhydraulicstructurefailureswastheactionofwater!

The best way of determining the flood peak flow and volume is to statistically analyse the historical

data.Forthatmethodtobereasonable,longmeasurementseriesneedtobeavailable.Theproblemis

thatinremotesmallcatchmentssuchmeasurementsareseldomavailable.However,ifinthevicinity

thereiswellknownstreamsforwhichsuchdataareexist,thenanattemptcouldbemadetomake

correlationoftheunknownstreamwiththeknownone.

This can be done through a series of simultaneous flow measurements in different hydrological

regimes. Even a series of 45 measurements could be used, but waiting for proper hydrological

conditionsusuallytakesuptoayear.

The known watercourse is analysed by taking the

highest flood hydrographs for each year (40 years or

moreareneededforreliabledata,butevenmuchlessis

betterthannothing).Observedfloodhydrographsareusually determined through water gauging pole or

limnighraph(automaticwaterlevelmeter).Priortothat,

many flow measurements had to be taken in order to

determine correlation between flowrate and the stage

/level. In such a way a flow rating curve (FRC) is

determined.

Analysed flood flows can then be determined through one of usually used statistical distributions

(mostcommonlyLogPiersonIIIorGumbel).Thisgivesfloodswithdifferentreturnperiodsthatcanbe

usedasDesignFloodDischarge(DFD),dependingontheimportanceofthestructureanddangertothesurroundingarea.


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21

Theproblemhereisthatcorrelationbetweencatchmentsmaynotbereliableoreventhatdatafrom

the known catchment may be dubious since it is very difficult to take measurements in flood

conditions.ThusFRCisusuallyextrapolatedtowardshighflowsandthusnotreallyobserved.

Anyway, in small remote catchments such data availability is unlikely ant therefore other, less

accurate,methodsareemployed.

Empirical formulae

Forveryroughflood levelestimation,wheretherearenodataortheyareverypoorsomeempirical

formulaecouldbeused,keepinginmindthattheobtainedvaluescouldbewithlargemarginoferror.

Nevertheless,thatisstillbetterthannothing.

Inglisformula:

QMAX=124 AC/ (10.4+AC)

Dickensformulae:

QMAX=a AC0.75

Whereais:

11fordry/aridclimatetype

17fornormalclimate

23forwetclimate

AndACiscatchmentareainkm2,whilepeakflowQMAXisinm

3/s.

Both formulae areneglecting thegeology, shapeand slopeof the catchment andwhether there is

vegetationandtowhatextent.Bothformulae(andespeciallyInglis)giveratherhighflowpeaks,which

is understandable sine high safety factor is taken into account. The values obtained are roughly

corresponding to PMF (Probable Maximum Flood), which is too high for design of MHPs. The

reasonableapproachwouldbetotake tooftheobtainedvalue.

Rational method (RM)

Iftherearegoodrainfalldatathismethodcanbeusedtobetterdeterminethepeakflood.

Q = C i AC (m3

/s)

Where:

CRunoffcoefficient(rangingfrom0.25to0.75,say0.5)

iIntensityoftheprecipitationinmm/min

ACCatchmentareainkm2

However intensity drops with increase of rainfall duration and selection of the proper duration

would depend on the size and shape of the catchment. There are many rational formulae to

calculatethedurationT.Hereisonethatneglectstheshapeofthecatchment:

T = 0.27 AC0,612


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Figure12ExampleofintensitycurvesforvariousreturnperiodsforSarajevo

Unit Hydrograph (UH)

However,forlargerMHPsitisalwaysadvisabletoperformatleastunithydrographcomputation,say

by using HECHMS free computer program. The program provides several methods to compute the

UH.PerhapsthemostpopularisSCSmethod(SoilConservationService)whichrequiresaminimumof:

Theprecipitationforadurationcorrespondingtocatchmentparameters

Catchmentarea

Catchmentshaperesultinginlagtime

SCS Curve number (see Table1SCScurvenumbers)

Table1SCScurvenumbers

Land Use

Description on

Input Screen

Description and Curve Numbers from TR-55

Cover Description

Curve

Number for

Hydrologic

Soil Group

Cover Type and Hydrologic Condition

%

Impervious

Areas

A B C D

AgriculturalRow Crops - Straight Rows + Crop Residue

Cover- Good Condition

(1)

64 75 82 85

Commercial Urban Districts: Commercial and Business 85 89 92 94 95

Forest Woods(2) - Good Condition 30 55 70 77

Grass/Pasture Pasture, Grassland, or Range(3) - Good

Condition39 61 74 80

High Density

Residential

Residential districts by average lot size: 1/8

acre or less65 77 85 90 92

Industrial Urban district: Industrial 72 81 88 91 93

Low Density

Residential


acre lot25 54 70 80 85


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Land Use

Description on

Input Screen

Description and Curve Numbers from TR-55

Cover Description

Curve

Number for

Hydrologic

Soil Group

Cover Type and Hydrologic Condition%

Impervious

Areas

A B C D

Open Spaces

Open Space (lawns, parks, golfcourses,

cemeteries, etc.)(4) Fair Condition (grass

cover 50% to 70%)

49 69 79 84

Parking and

PavedSpaces

Impervious areas: Paved parking lots, roofs,

driveways, etc. (excluding right-of-way)100 98 98 98 98

Residential 1/8

acre


acre orless65 77 85 90 92

Residential 1/4

acre


acre38 61 75 83 87

Residential 1/3

acre


acre30 57 72 81 86

Residential 1/2

acre


acre25 54 70 80 85

Residential 1

acre

Residential districts by average lot size: 1

acre20 51 68 79 84

Residential 2

acres

Residential districts by average lot size: 2

acre12 46 65 77 82

Water/ Wetlands 0 0 0 0 0

Hydraulic condition isbasedon combination factors that affect infiltration and runoff, including (a)

densityandcanopyofvegetativeareas,(b)amountofyearroundcover,(c)amountofgrassorclose

seeded legumes, (d)percentof residueon the landsurface (good>=20%),and (e)degreeofsurface

roughness.

Majorcatchmentparameters,apartfromitsarea,are:

LG=unithydrographlagtime,inhours,

C=constant,(=26n,nisManningcoefficientrangingfrom0.03to0.07)

N=constant(usually0.33)

L=thelengthofthelongestwatercoursefromthepointofconcentrationtotheboundaryofthedrainagebasin,inmiles.Thepointofconcentrationisthelocationonthewatercoursewhereahydrographisdesired,

LCA=thelengthalongthelongestwatercoursefromthepointofconcentrationtoapointoppositethecentroidofthedrainagebasin,inmiles,and

S=theoverallslopeofthelongestwatercourse(alongL),infeetpermile.

Lagtimeiscalculatedfrom:

N

CA

GS

LLCL

5.0

TimeofconcentrationTC=5/3LG(seeFigure13Exampleofafloodhydrograph)

RelevantprecipitationdurationTP=TCx(1+TC)0.2


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Since lagtimeisempiricallydeterminedthereareotherformulaeaswell.Somemetricformulaegive

theLagtimeas:

LG=1.864 AC0.39

S0.31

LG=0.4 Ls0.67

(L LCA/S)0.086

LG=2.3 (L/(S)0.5)0.66

Incaseofdoubtusethemeanvalueofallthreeorjusttwothatgivecloserresults.

After that, knowing precipitation, one can compute the flood hydrograph by using manual unit

hydrographprocedureorrunningtheHECHMSprogram.

Figure13Exampleofafloodhydrograph

1.2.3. Measurements

Thepurposeofahydrologystudyistopredictthevariationintheflowduringtheyear.Sincetheflow

variesfromdaytoday,aoneoffmeasurementisoflimiteduse.Inabsenceofanyhydrological

analysis,alongtermmeasuringsystemmaybesetup.Suchasystemisoftenusedtoreinforcethe

hydrologicalapproachandisalsothemostreliablewayofdeterminingactualflowatasite.Oneoff

measurementsareusefultogiveaspotcheckonhydrologicalpredictions.

Theflowmeasuringtechniquesdescribedhereare:

theweirmethod,

stagecontrolmethod,

thesaltgulpmethod,

thebucketmethod,

thefloatmethod,

currentmeters.


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c) Measuringweirs

Aflowmeasurementweirisaweirwithanotchinitthroughwhichallthewaterinthestreamflows.

The flowrate can be determined from a single reading of the difference in height between the

upstreamwaterlevelandthebottomofthenotch(seeFigure14).Forreliableresults,thecrestofthe

weirmustbekeptsharp, theoverflowshouldnotbesubmergedbytailwater andsedimentmustbe

prevented from accumulating behind the weir. Sharp and durable crests are normally formed from

sheetmetal,preferablybrassorstainlesssteel,asthesedonotcorrode.

Figure14Flowmeasurementsusingweir

Weirscanbetimber,concreteormetalandmustalwaysbeorientedatrightanglestothestreamflow.

Sitingoftheweirshould beata pointwhere thestream isstraightandfreefromeddies.Upstream,

thedistancebetweenthepointofmeasurementandthecrestoftheweirshouldbeatleasttwicethe

maximumheadtobemeasured.Thereshouldbenoobstructionstoflownearthenotchandtheweir

mustbeperfectlysealedagainstleakage.

Temporary measuring weirs are used for shortterm or dryseasoned measurements and are usuallyconstructedfromwoodandstakedintothebankandstreambed.Sealingproblemsmaybesolvedby

attachingalargesheetofplasticandlayingitupstreamoftheweirhelddownwithgravelorrocks.Itis

necessarytoestimatetherangeofflowstobemeasuredbeforedesignedtheweir,toensurethatthe

chosensizeofnotchwillbecorrect.

The use of permanent weirs may be a useful approach for small streams, but larger streams might

betterbemeasuredbystaging(explainedbelow).

d) Stagedischargemethod

Oncesetup,thismethodprovidesan instantmeasurementoftheflowatanytime.Itdependsona

fixed relationship between the water level and the flow at a particular section of the stream. This


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26

section (the contour section) is calibrated by taking readings of water levels and flow (stage and

discharge)forafewdifferentwaterlevels,coveringtherangeofflowsofinterest,soastobuildupa

stagedischarge curve. During calibration the flow does not have to be measured at the contour

sectionitself.Readingscanbetakeneitherupstreamordownstreamusing,forinstance,atemporary

weir,aslongasnowaterentersorleavesthestreaminbetween.Thestagedischargecurveshouldbe

updated each year. Calibrated staffs are then fixed in the stream and the water level indicated

correspondstoariverflowratewhichcanbereadoffthestagedischargecurve.

Figure15Flowmeasurementsusingfloat

e) 'Saltgulp'method

The `salt gulp' method of flow measurement is adapted from dilution gauging methods with

radioactivetracersusedforrivers.Ithasprovedeasytoaccomplish,reasonablyaccurate(error


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27

Figure16Flowmeasurementsusingdilution

Theaboveargumentassumesthatthecloudpassestheprobeinthesametimeineachcase.Butthe

slowertheflow,thelongerthecloudtakestopasstheprobe.Thusflowisalsoinverselyproportional

to the cloudpassing time. Detailed mathematics will not be covered here because the conductivity

metreisusuallysuppliedwithdetailedinstructions.

Theequipmentneededfor`saltgulp'flowmeasurementis:

abucket, puretablesalt,

athermometer(range0 40C),

aconductivitymeter(range01000mS),

anelectricalintegrator(Optional).

f) Bucketmethod

Thebucketmethodisasimplewayofmeasuringflowin

very small streams. The entire flow is diverted into a

bucketorbarrelandthetimeforthecontainertofill isrecorded. The flow rate is obtained simply by dividing

thevolumeofthecontainerbythefillingtime.Flowsof

upto20l/scanbemeasuredusinga200litreoilbarrel.

g) Floatmethod

TheprincipleofallvelocityareamethodsisthatflowQequalsthemeanvelocityVmeantimescross

sectionalA:

Q=AVmean(m3/s)


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Onewayofusingthisprincipleisforthecrosssectionalprofileofastreambedtobechartedandan

averagecrosssectionestablishedforaknownlengthofstream.Aseriesoffloats,perhapsconvenient

piecesofwood,arethentimedoverameasuredlengthofstream.Resultsareaveragedandaflow

velocityisobtained.Thisvelocitymustthenbereducedbyacorrectionfactorwhichestimatesthe

meanvelocityasopposedtothesurfacevelocity.Bymultiplyingaveragedandcorrectedflowvelocity,

thevolumeflowratecanbeestimated.

h) Currentmeters

Theseconsistofashaftwithapropellerorrevolvingcupsconnectedtotheend.Thepropellerisfree

to rotate and the speed of rotation is related to the stream velocity. A simple mechanical counter

records the number of revolutions of a propeller placed at a desired depth. By averaging readings

takenevenlythroughoutthecrosssection,anaveragespeedcanbeobtainedwhichismoreaccurate

thanwiththefloatmethod.

Figure17Flowmeasurementsusingcurrentmeters

i) Automatedmeasurements

Therearealsosomesophisticatedpiecesofequipmentthattakeautomaticflowrateandcrosssection

readings byjust pulling the device across the stream. These are used for larger rivers difficult to

measurebytraditionalmethods.OnesuchdeviceiscalledRiverCATandisratherexpensive(sayabout

$30000ormore,dependingonthytype).

Figure18RiverCATinaction


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29

1.3. GeologyandGeomechanics

1.3.1. Overview

Whatis

important?

1. Essential:

a. Determiningthetypeofsoil

b. Determiningthetypeofthebedrock

c. Determiningthedepthofoverburden

d. Lookforactualorpotentiallandslidesandscrees(slidingdebris)

e. Roughestimationofgeotechnicalparameters(bad,poor,fair,good,excellent)


a. Makinggeologicalmapofthearea

b. Preparingcharacteristicgeologicalprofiles

c. Determiningactualgeotechnicalparameters(c, , ,etc.)


P>100kW.

Geology(geologicalconditionsandformations)canbegenerallydeterminedfromregionalgeological

maps if available. However, for site specific conditions it is necessary to make site geological

assessmentinsitu.

Figure19ExampleoftheuseofGoogleEarthinanalysingthearea


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30

Figure20Exampleofthegeologicalprofiletakenfromthegeologicalbasemap1:100000

Figure21Exampleofthegeologicalbasemap1:100000

Figure22Landslides


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31

Figure23

Screes

Itisimportanttodeterminegeneralgeologicalsiteconditionstakingintoaccountengineeringgeology

andhydrogeology.Itisusedforproperassessmentofthesoil/rockparametersintermsoffoundation,

buildingmaterial,permeabilityetc.Thisgeologyislinkedto:

Geomechanics Hydrology Structuraldesign Hydraulicdesign

Tofindoutaboutgeotechnicalparametersandengineeronthesitecanuseapickhammer,excavatea

testpitortrenchandbasedonexperiencemakeengineeringjudgments.Formorerequiringstructures

(inlargerschemes),itwouldbeadvisabletousesomedrillingandtakesamplesthatwouldbeanalyses

in the geotechnical laboratory. Obtained parameters could be used to run a number of different

analyses.Oneofthecommonlyusedisslopestabilityanalysis:

Figure24Slopestabilityresults

One very good such computer program for geotechnical analyses is GEO5 by FINE, which has 22

differentmodules(fromslopestability,tofoundation,gabionwall,gravitywalltoFEM).Eachmodule


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32

costsabout$400to$600,butdiscountscanbeobtainedforasetandmultipleusers.Theprogramhas

a free option with limited functionality. It will run only a few soil layers (and we usually dont need

manyforMHPs)anditwilluseonlydefaultparametersoftheselectedsoiltypeandwouldnotallow

youtochangethemtothoseobtainedfromthesite.Thisisstilluseful,sinceitgivespossibilitytouse

standardparameterswithouttakingsamples.Thentheonlystepneededistorecognizethesoiltype

andselectit.

Other similar programs are GeoStudio and Slope. Figure 24 shows an output from Geostudio

program.

Figure253Dsitegeologicalpresentation


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33

2. Basicsofhydraulics2.1. Overview

Whatisimportant?

1. Essential:

a. Performingsteadystatecalculationsfor

i. Canals(headrace,tailrace)

ii. Pipelines,penstocks

b. Hydrauliccalculationatintakeifany

c. Hydraulicandsettlementcalculationatsandtrapifany

d. HydrauliccalculationatForebay

e. Hydrauliccalculationforspillways(atintake,sandtrapandforebay)

f. Hydrauliccalculationforoutlets(sandtrap,forebay)

g. Hydrauliccalculationofthestillingbasin(orapron)ifany


a. Performingunsteady(transient)computations

i. Channelunsteadyflow

ii. Penstockwaterhammer


P>100kW.

2.2. PipelinesPipelinesareusedforwaterorsewerconveyanceusuallyunderpressure,butalsowithfreeflow.They

canbemadeofvariousmaterialssuchas:Steel,GRP,PE,castiron,concrete,wood(obsolete),vitrified

clay(obsolete),asbestoscement(consideredenvironmentallydangerous),plasticmaterials(PVC)and

othermaterialsforspecialpurposes(brass,copper,lead,glass,rubber,etc.).

Hydraulics

Mostoftheprincipleswillbegiveninthissubchapterofpipelines,andonlysomespecificissueswould

bementionedforcanalsandtunnelsintheirrespectivesubchapters.

Basic hydraulic problems for steady flow through pipelines can be solved by 2

formulae:

Continuity(massconservation):Aivi=Constant

Bernoulli(energyconservation): 21

2

222

2

111

22

H

g

v

g

pZ

g

v

g

pZ


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34

H isthesumofhead lossesbetweensectionsof interest.They include linearfriction lossesalong

thepipeandlocalorminorlosses(inbends,elbows,joints,valves,contractions,expansions,etc.).

Numerousformulaeareavailabletocomputelinearfrictionlosses.Probablythemostuniversallyused

is DarcyWeisbach formula: g

v

D

L

fHf 2

2

(in USA practice HazenWilliams expression is more

commonlyused)

HerefisDarcysfrictioncoefficient.Differentresearchershavedetermineditsvalueinthepast.There

arevariousexperimentallyobtainedexpressionsusedtodeterminef.

Therearedifferentflowregimespossibleinthepipes,dependentonReynoldsnumber:

Re=vD/orReR=vR/R=D

/4isHydraulicradiusofthepipe.iskinematiccoefficientoffluids

viscosity(forwater:t=20o=1.01x106m2/s,andt=10o=1.3x106m2/s)

ForRe


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Table2Piperoughness

Materialandthestateofpipe (103m)

Concreterough 13

Concretesmooth 0.30.8

Steel(welded)new 0.040.1

Steel(welded)used,stained,incrusted 0.151.5Castiron 0.251.5(4)

Moredetailedlistcanbeobtainedfromdifferenthandbooks(e.g.Davis).Asmostpracticalproblemsin

hydraulic(civil)engineeringoccurintheregionofquadraticresistance(fullturbulence),evenmanning

formula could be applied with reasonable accuracy. Then better known values for n can be used

and/orconvertedtof.EquatingenergyslopeinManningandDarcyWeisbachequations:

326.124 Dnf

However, this could be applied only in fully developed turbulent flow as in transitional regime

Manningnshould not be considered constant as it is there dependent on Re as well. (See following

graphthatclearlydemonstratesthisforasetofmeasurements).

Figure26n=f(R)relationshipintransitionalflowzone

HazenWilliamsformula:


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Where:

A=Flowareaofthepipe,ft2orm2.

C=HazenWilliamsroughnesscoefficient.

D=Pipediameter,ft.orm.

g=gravitationalconstant=32.174ft/s

2

=9.807m/s2

.hf=Frictionlosses,ftorm.

hm=Minorlosses,ftorm.

k=conversionfactor=1.318(forimperialunits)=0.85(forSI)

Km=sumofminorlosscoefficients

P1=Upstreampressure,lb/ft2orN/m2.

P2=Downstreampressure,lb/ft2orN/m2.

Q=Discharge,ft3/sorm3/s.

S=Waterdensity =62.4lb/ft(forimperialunits)=9800N/m(forSI)

V=flowvelocityinpipe,ft/sorm/s.

V1=upstreamvelocity,ft/sorm/s.

V2=Downstreamvelocity,ft/sorm/s.

Z1=Upstreamlevel,ftorm.

Z2=Downstreamlevel,ftorm.

Table3Importantpipematerialproperties

Ductileiron Steel PVC PE/GRP AC

Manningn 0.12 0.013 0.01 0.011 0.011

HazenWilliamsC 130 100 150 140 140

Roughness(mm) (DarcyWeisbach) 0.2591 0.04572 0.00152 0.00152 0.00152

YoungModulusE(MPa) 100000 207000 3300 1300/73500 24000

Coefficientoflinearexpansion (x10

6) 11 12 54 140/5 8.1

Poissonratio 0.25 0.3 0.45 0.45 0.3

Minororlocallossesarecalculatedbasedonexperienceandexperiments.Somecoefficientsto

calculatelocallossesaregivenhere:

Entrance:sharp=0.5,rounded=0.2,bellmouth=0.05,pipestickingintoreservoir

=1

Suddenexpansion:

22

2

11

D

D inregardtoinflowingvelocity.Ifexpansionisgradual

then this coefficient would be diminished (by multiplier k


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37

Elbow:

5.3

285.113.0

901.0

R

Dor

R

D

R

Lo

whereL isarc length,R isbend

radius,Dispipediameter,andisdeflectionangleofthecurve.

Valves and gates: ifopen0.05


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stress=pD/eforunitlengthofpipe.Hereeispipeshell(wall)thickness(orequivalentthicknessoftensiontakingpart).Thicknesscouldbecalculatedfromhere if insteadoftensilestress,allowable

tensilestress (forgivenmaterial) isused.Usualprocedurewouldbe tocompute this thickness first,

taking into accountpressure transients. This procedure requires iterations since thepipe thickness

affectspressurewaveceleritya,whichisrelevantfordeterminationofpressureriseH.

Changeofheadforquickclosure/openingcanbeexpressedby:

g

avH 0 Zhkovskycasefullwaterhammer

Whereaiscelerityofthepressurewave:

e

Dk

eE

D

K

a

50

10

1

1 4

Forwater=1000kg/m3,bulkmodulusK20108N/m2,k=1011/E

ForsteelE201010N/m2,k=0.5;Dispipelinediameter,eispipewallthickness.

Forothermaterials:k=1(castiron),k=5(concrete,lead),k=10(wood,plastic)

Openingorclosureisconsideredtobequickifitsshorterthantimeneededforpressurewaveto

traveltotheupperreservoirandback(0T,=2L/a).

Iftheopeningorclosuretakeslongerthanpressurechangeisdiminished:gT

LvH 02 .Ifalongthe

pipelinecrosssectionchanges,eachchangegeneratestransmissionandreflectionpressurewavesthat

superimposewithoriginalonesandaffecttheresults.Forbranchingorloopingnetworksthesemust

betakenintoaccount,andcomputationbecomesrathermorecomplicated.Ifthepumpingstations

areplacedalongtheconveyanceitisoftendifficulttocontroltimesofopeningand(especially)

closure,thusdifferentmeasurescanbeappliedtocontrolthedrop/riseofhead:

Flywheelsifcoupledwiththepumptheyprovideadditionalinertiasothatpumprotatesawhile

afterpowercutoccurs.Suitableforsmallinstallations.

Bypassesandpressurereliefvalvesbypasswithnonreturnvalvesuckspartoftheoriginalflow

mitigating thenegative effectsof sudden stoppage.Pressure release valves and air inlet valves

couldbeprovidedinthepipelineasadditionoralternatively.

Surge tanksandairvesselshave tobeplacedasclose to thepump(s)aspossible.Therefore,

often it isnotpracticable touseopen surge tanks (for theywould require enormousheights).

Rather,closeairvesselswithaircompressorsaremorecommonlyused.Theyconvert(orlimitin

space)more severewaterhammereffects tomilder (and longer/slower) surge (massoscillation)

effects.

Airvesselsservebothforsuddenopeningandclosure.Acheckvalveshouldbeprovidedbetweenthe

pumpandairvessel.Predeterminedextremelevelsintheairvesseltriggerthecompressedair

delivery.

Neglectingheadlosses,simplifiedsolutionforsuddencompleteclosure(intermsofheadchange)is:


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39

t

LV

gAH

gAV

LHQHH

0

0

0

0

00 sin

0

000min

gAV

LHQHH

FromhereVmaxcanbecomputed:

Vmax1.2Hmin=V0

1.2H0

Periodofoscillationis:

0

0

2

LV

gAHT

Including losses in the pipeline and (entrance into/exit from) the air vessel, computation gets

somewhatmore complicated and isusually solvedby finitedifference equationorbyusingdesigngraphs forgiven (orassumed)head losses.Forpipelineswithchangingdiametersequivalent length

(onediameter lengththatwouldhavesamehead lossesasoriginalpipe)canbeused insimplified

computations.

Ifthepipethickness(obtainedinthisway)islessthancertainstructuralminimum,thanthislatervalue

shouldbeadopted.Structuralminimumwoulddependonmaterialusedandpipediameter(forsteel

pipesthisshouldbe8mmormoreforlargerpipes,includingupto2mmprovisionforcorrosionand

abrasion lossesof themassduringoperation).Suchdimensions shouldbechecked ifcanwithstand

otherloads,andadjustedifnecessary.

Usually temperature induced loads should be alleviated using deformable coupling elements

(expansionjoints) that canaccommodate resultingdeformations.Due to temperature changespipe

wouldtendtoexpand(contract)betweentwofixedpoints(anchorblocks)dependingontemperature

differencebetweenparticularmomentandambienttemperatureduringpipeplacement.Temperature

linearexpansioncoefficient is(m/moC).Forsteel it isabout12x106.Withoutanchors,extensionof

thepipeslengthwouldbe:L=Ltt.Ifexpansionisdisabledbyanchorblocksreactingstresswoulddevelop:

= EL/L,E ismodulusofelasticityofmaterial (forsteel20x1010Pa).Thesestressesand resultingforcescanbeunacceptable,andtodiminishthemspecialpipelineconstructionarrangementscanbe

introducedeitherexpansionjointsorharpshapedpipelinedeformableparts.

For freesurface or lowpressure pipes, loads caused by burying, backfill and surcharge are more

important.Iftheyarenotburied,thenstructuralthicknessdependentonthematerialusedandpipes

diameter, shouldbe adopted. For concrete pipes t=1/12D,but not less than 15 cm (D innerpipe

diameter).


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Theplatethicknessrequiredtoresistbucklingunderuniformexternalpressureisapproximately:

36

6.1 pE

De

Ownweightofthepipeandwaterinitmustbetakenintoaccountforcalculationoftheforcesacting

on supports and anchorblocks. Friction, inertial,deflection (centrifugal) andother effectsmust be

accountedfor.

Placement considerations

Pipescanbeburiedoropen.Botharrangementshaveadvantagesanddisadvantages.Decisionistobe

madebasedonprojectneeds,localconditionsandthelike.

Buriedpipes:

Advantages Keepwater temperaturepretty constant andprotect from freezing;Ambienttemperaturesdonot imposeextra loads (savingsonexpansionjoints);Onceplaced theydo

notconsumeextraspace;Frequentanticorrosionpaintingnotneeded

Disadvantages difficult accessibility for maintenance; Backfill pressures; Expensive trench

excavation,beddingmaterial,carefulbackfilling;difficultplacementlimitedspaceforwork;

Painfuldetectionofleakageandotherproblems.

Openpipes:

Advantagessimpleaccessibilityformaintenance;Nobackfillpressures;Noexpensivetrench

excavation,beddingmaterial,carefulbackfilling;Simplifiedplacementplentyof space for

work;Easydetectionofleakageandotherproblems

Disadvantageswater temperature affected by ambient and no protection from freezing;

Ambienttemperaturesimposesevereextraloads(expensiveexpansionjoints);theyoccupya

lotofvaluablespace;Frequentanticorrosionpaintingneeded;Anchorblocksandnumerous

supports.

Economic considerations

Importanceofoptimizedlayout.Severalalternativesshouldbecompared.Savinginlengthand

diameter/wallthickness(aswellaspumpingfacilities)

Selectionofeconomicconduitsize(Pumpingstations,HPP,etc.).Incasewhenplentyofheadis

available (nopumpingneeded,ornoHPP foreseen/feasible) then considerationofminimum

diametermax.allowablevelocityandavailableenergyhead.

Comparisonorcombinationwithothertypesofconveyancesifapplicable.

Intermsofmaterialsforthepipesinhydraulicconstruction(largerscale)mostcommonaresteeland

concrete. Asbestoscement introduced after the other two, seemed to be promising due to its

favorableproperties(durability,easeofplacement,etc.),butlatelyitissuspectedtoberesponsiblefor

potentiallycausingcancer,andisnolongerconsideredenvironmentfriendlymaterial.

Steelpipesaremostlyweldednowadays,thoughothertypesofjointsarestillused.Theyarerelatively

expensive and require protection (and maintenance) against corrosion. Otherwise, they are


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41

comparatively easy to handle, they can stand extreme pressure and tension stresses, easy to make

fittings,joints,branches,expansions,contractions,bends,andwhateverelseneeded.

2.3. Canals

Inasimilarmanner,theopencanalscouldbeanalyzedinordertoobtainparametersforpreliminary

design.ForhydrauliccomputationsManningformulawasused:

SARn

Q 32

1

Fromherecrosssectionisoptimizedforvariouslateralcanalslopes.Overalloptimumwithsidesat60o

is in most cases not technically feasible from the construction viewpoint. Therefore, as earlier

mentionedfollowing,morecommon slopes wereused V: H=1: m(form=0, 1,1.5and 2). (Here mi =

1/Si)

Figure27 Typicalcanalsection

Inordertofitthecanalintothegroundafreeboardshouldbedeterminedaswell.Traditionallythisis

between30and120cmandusuallytakenas30cm+0.25.h(wherehisthewaterdepthinthecanalin

cm).Alsoinamoregeneralformalateralslopeoftheterrainshouldbeconsideredinordertofitthe

canalandcalculatethebillofquantities:

Figure28 Typicalcanalsectionwithlateralgroundslope

The quantities will generally increase for increased lateral terrain slope for the HJK value. In the

present model this has been ignored and taken into account as contingencies or the lump sum for

unforeseenworksintheformofpercentagebasedongeneralengineeringjudgmentfortheparticularsiteconditions.

The same type of the conveyance formula, as the one for pipes, is derived for those types of

trapezoidal canals. Instead of filling coefficient as in pipes, optimal ratio of h/B would determine a

coefficientintheformula:

8

3

S

QnD

Table4Canalflowcalculationsparameters

m OPT.B/h Applicable

0 2 1.834 m=0


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m OPT.B/h Applicable

1 0.84 1.81.e (0.833.m) m1

1.5 0.62 0.592.Log(m)+0.7854 1


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43

Figure30Typicalchangesofflowregimes

2.4. Tyroleanintake


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44

Figure31Tyroleanintake

2.4.1. Intake


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45

AfterP.NovakAppliedHydraulics,IHEDelft,1981.

E

hh

E

hh

crx 11

1 11

Distancefromthebeginningoftheintake

Where

r=0.57ratiooftheintakebreadthtoriverbreadth

c=0.45coefficient(0.40.5afterMostkov)forlongitudinaltrashrackbars.

h1=hCRwaterdepthatthebeginning(forx=0)

hDepthforwhichdistancefromthebeginningisdetermined

EEnergyoftheflow

Forallwatertobetakeninthedepthattheendwouldbeh=0,thus:

E

hh

crbz

11 1

1

Forexampleofthedischarge:

Qz=0.21m3/s

Onethird oftheareaisblockedbybarsandbytheleavesanddebris:

Table

5

Example

of

the

calculation

for

Tyrolean

intake

Q L q hc b

B

(increased) Bpot

0.21 2.00 0.105 0.10 0.25 0.38 0.75

0.21 2.50 0.084 0.09 0.22 0.32 0.65

0.21 3.00 0.070 0.08 0.19 0.29 0.57

0.21 4.00 0.053 0.065 0.16 0.24 0.47

0.21 5.00 0.042 0.06 0.14 0.20 0.41

Figure32Waterprofileontheintake

h

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18


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46

Otherapproach:

Bz= Breadthofthecanal

Lz= Lengthofthecanal

br= Heightoftherackc= Coefficient

q= Unitdischarge

hkr= Criticaldepth

h= Depthofwaterontherack

Dh= Freeboardofnonspillwaysection

bpot= Neededwidth

AfterHajdin,Sarajevo1966.

AndafterI.Valant,Ljubljana1986.

Data:

Bz= 0,914xQ0,4

Lz= 7xBz

br= Bz/cosb

c= 0,6x(a/d)xcos1,5b

q= Q/Lz

hkr= 0,476xq0,6667

h= kxhkr

Dh= 1,5xhkr

bpot= 0,3386*(q/(cxmxh0,5

)

Qinst= 0.21 m3/s

Slopeoftherack= 10 %

a= 20 mm

d= 30 mm

m= 0.65 (forflatiron)

k= 0.91 (forb=10o)

Q Bz Lz b beta c qs hc h h Bpot k mu ar d0.21 0.490 3.43 0.492 0.100 0.357 0.061 0.073 0.066 0.091 0.348 0.91 0.65 15 25

2.4.2. CollectioncanalLengthofcollectioncanalundertherackisdonebyempiricalformula:

AfterP.NovakAppliedHydraulicsIHEDelftand1981,HydraulicStructures,London1990:

Computationofthewatersurface

Q 0.21

B 0.6

n 0.02


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47

So 0.025

hc 0.232

L 4

Rackheight 0.04

Elevationoftherack 254.4

Elevationofthecanalbeginning 253.66Elevationofthecanalend 253.56

Scr 0.013704

xSSQ

Qvv

QQg

vvQh

f

0

1

2

21

211

WhereS0bedslope, Sfenergyslope

Figure33Waterprofileonthecollectioncanal

2.4.3. Spillwayonthesill(Q1/100)Discharge:Q1/100=35m

3/s

233

232 2 HBCHBgCQ

Dischargecoefficient:C2=0.40,orC3=1.77

BSpillwaybreadth

HSpillwaydepth

Elevationofthesill254.50mASL.

Elevationofthespillway254.70mASL.

Bp 4.0 BreadthofTyroleanpart

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450

0.500

0 0.5 1 1.5 2 2.5 3 3.5 4

h

h+v2/2g


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48

B 7.0 Breadthofthesill total

Qsr 0.24

DischargesQ1/100 35

Qi 0.37

Qmin 0.0125

Pu 0.95 SillheightupstreamPn 1.7 Sillheightdownstream

Hp 1.88 Heightofspillingpart

Ht 2.08 HeightofTyroleanpart

m 0.4 SpillwayCoefficient

hc 1.37 Criticaldepth

Eo 3.78 Availableenergy

Floodwaterelevation=254.50+2.08=256.58mASL.

Orroughly256.60mASL.

2.4.4. Stillingbasin(Q1/100)2

1

2

2

12 yg

qyE

,availableenergy

3

1

2

1

2 8112 gy

qyy ,conjugatedepths(y1iy2)

Stillingbasin(SB)length:

Lb=K(y2y1)Where4.5


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49

DepthattheSBend:

S 1.20% Bedslopedownstream

n 0.02 Roughness(Manning)

h 0.94 DownstreamdepthendofSB

Fr 1.87 Froude number

Checkup

Manningsformula:

SARn

Q 32

1

Where:

QDischarge

nRoughnesscoefficient

ACrosssectionalarea

RHydraulicradius

SRiverbedslope

Graduallyvariedflow:

2

0

2

0

11 rF

SS

x

y

Fr

SS

dx

dy ff

Where:

SoRiverbedslope

SfEnergyslopeFrFroudenumber

EndofSBdepth:

S 1.20% Downstreamslope

n 0.028 Roughness

h 1.37 DownstreamdepthendofSB

Fr 1.06 Froudenumber

Figure34

Water

profile

along

SB

252.6

252.8

253

253.2

253.4

253.6

253.8

0 1 2 3 4 5 6 7 8

kota dna

kota vode


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50

Figure35WaterprofilealongSBanddownstream

Waterdepthdownstream:

bk 4.5 Riverbedbreadth

S 1.20% Downstreamslope

n 0.033 Roughness

m 1.25 Sideslopes

A 10.9 Area

Bw 10.9 Watersurfacebreadth

h 1.42 DepthattheendofSB

Fr 1.02 Froudenumber

2.4.5. Settlingbasin(Qi)

H1= Waterdepthatthebeginning H1= k1xh0

k1= Coefficientoftransitionv0tovT k1= 1,6xQ0,1

BT= Settlingbasinbreadth BT= ST/H1

LTC.= Lengthofthesettlingbasin(theoretical) LTra.= H1x(vT/u)

LT= Lengthofthesettlingbasin(adopted) LT= 1,6xLTra.

Exampledata:

Discharge Qinst= 0.21 m3/s

Depthatthebeginningoftransition h0= 0.85 m

Breadthofthecollectioncanal b0= 0.60 m

Adoptedflowvelocity vT= 0.3 m/s

Adoptedsedimentfallvelocity u= 0.025 m/s

Adoptedbedslope I= 2 %

252.4

252.6

252.8

253

253.2

253.4

253.6

253.8

254

0 2 4 6 8 10 12 14 16

kota dna

kota vode


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51

Q h0 b0 v0 vT ST H1pot BT BTusv u L LT LTusv

(m3/s) (m) (m) (m/s) (m/s) (m

2) (m) (m) (m) (m/s) (m) (m) (m)

0.210 0.85 0.80 0.31 0.15 1.45 1.16 1.24 1.70 0.03 6.76 10.82 11.20

CheckupbyStokesLaw:

Table6Settlingvelocityoftheparticledependentonwatertemperature/viscosityoC

t 20 12 10 8 6

A m2 1.25 1.25 1.25 1.25 1.25

Q m3/s 0.37 0.37 0.37 0.37 0.37

VAV m/s 0.30 0.30 0.30 0.30 0.30

d mm 0.20 0.20 0.20 0.20 0.20

vSET m/s 0.033 0.026 0.025 0.024 0.022

hAV m 0.85 0.85 0.85 0.85 0.85

L m 11.20 11.20 11.20 11.20 11.20

TSET s 25.99 32.20 34.00 36.17 38.29

t flow s 37.84 37.84 37.84 37.84 37.84


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52

Otherapproachcanusethefollowingformulae:

Basinlength:h/vD


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53

HpHbottom 0.93

b 0.4

h 0.4

A 0.16

H 0.73

m 0.7

Q 0.424

Qout=424l/s

Timetoempty=?

Volumeca.

V 15.90 m3

hmax 0.73 mD 0.4 m

A 0.16 m2

m 0.7

Q 0.42 m3/s

Timetoempty 75 s = 1.25 min

Forpartiallyclosedgate:

10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.05 0.10 0.15 0.20 0.24 0.28 0.32 0.36 0.39 0.42

Q=f(opening)

Propusna mo ispusta

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Otvor zatvaraa

Q(m3/s)

y

ydy

c

A

ga

HT

a

a

H

Hy

H

Hy

a

12

2

22

11


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54

2.4.2. Spillwayfromsettlingbasin(Qmax)

After G.A.Simonjan(1960.):

gvvLSShh f

29,0 21012

27,023,008,02

2

2

2

2

B

LhL

B

Lhm

23

22 HLgmQ

So 0.02

B 1.7

n 0.02

m 0.113

L 3

Hp2 0.832

v1 0.614

v2 0

P 0.87

h2 1.702

A 2.894

R 0.567m(Hp2) 0.113

m= 0.08*(h2*L/B2)^20.23*((h2*L/B

2)

2)+0.27

Sf2 0.013%

h2h1=(SoSf)*L+0.9(v12v2

2)/2g

h1 1.635

A 2.783

R 0.560

Hp1 0.765

Sf1 0.015%

2.4.3. Dutyflowoutlet(Qmin)Firstapproach:

gHACQ 2

D

Lf

c1


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55

Where:

fCoefficientDarcyWeisbachg

v

D

LfHf

2

2

.

32

6.124 Dnf =0,029

sumofminorlosses(1.5)

LPipelength

DDiameter

C=0.762

Secondapproach:

Re=vD/orReR=vR/R=D/4=157000

ColebrookC=0.762

Thirdapproach:

For 3


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56

3. HydropowerbasicsandHydraulicstructures3.1. General

Thebasicprincipleofhydropower isthat ifwatercanbepiped fromacertain leveltoa lower level,

thentheresultingwaterpressurecanbeusedtodowork.Ifthewaterpressureisallowedtomovea

mechanical component then thatmovement involves the conversionof thepotentialenergyof the

water intomechanicalenergy.Hydro turbines convertwaterpressure intomechanical shaftpower,

whichcanbeusedtodriveanelectricitygenerator,agrindingmillorsomeotherusefuldevice.

3.2. HistoryThe use of falling water as a source of energy is known for a long time. In the ancient times

waterwheels were used already, but only at the beginning of the nineteenth century with the

inventionofthehydroturbinetheuseofhydropowergotanewimpulse.

Smallscalehydropowerwasthemostcommonwayofelectricitygeneratingintheearly20thcentury.

In 1924 for example in Switzerland nearly 7000 small scale hydropower stationswere in use. The

improvement of distribution possibilities of electricity by means of high voltage transmission lines

causedfaintedinterestinsmallscalehydropower.

Renewed interest in the technologyof small scalehydropower started inChina.Estimates say t

Documents

Lecturenote Micro hydropower development