Water harvesting and its technique

water harvesting, runoff harvesting, rain water harvesting, roof water harvesting, flood water harvesting, farm pond

1. Subject
Soil and Water Conservation
Engineering
Topic
Water Harvesting and its
Technique
by
Dr. Sanjay Singh Chouhan
Assistant Professor
JNKVV-College of Agriculture
Powarkheda, Hoshangabad

2. Water Harvesting
•In general, water harvesting is the activity of direct collection of rainwater.
•The rainwater collected can be stored for direct use or can be recharged into the
groundwater.
•Rain is the first form of water that we know in the hydrological cycle, hence is a primary
source of water for us.
•Rivers, lakes and groundwater are all secondary sources of water.
•In present times, we depend entirely on such secondary sources of water.
•In the process, it is forgotten that rain is the ultimate source that feeds all these secondary
sources and remain ignorant of its value.
•Water harvesting means to understand the value of rain, and to make optimum use of the
rainwater at the place where it falls.
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3. Benefit of Water Harvesting
•Improvementinthequalityofgroundwater.
•Riseinthewaterlevelsinwellsandborewellsthat
aredryingup.
•Mitigationoftheeffectsofdroughtandattainment
ofdroughtproofing.
•Anidealsolutioninareashavinginadequatewater
resources.
•Reductioninthesoilerosionasthesurfacerunoff
isreduced.
•Decreaseinthechokingofstormwaterdrainsand
floodingofroads.
•Savingofenergytoliftgroundwater. 3

4. 1.RainwaterHarvesting
Rainwaterharvestingisdefinedasthemethod
forinducing,collecting,storingandconserving
localsurfacerunoffforagricultureinaridand
semi-aridregions.
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Types of Water Harvesting

5. Three Types of Water Harvesting are Covered by Rainwater Harvesting
•Watercollectedfromrooftops,courtyardsandsimilarcompactedortreated
surfacesisusedfordomesticpurposeorgardencrops.
•Micro-catchmentwaterharvestingisamethodofcollectingsurfacerunofffroma
smallcatchmentareaandstoringitintherootzoneofanadjacentinfiltration
basin.Thebasinisplantedwithatree,abushorwithannualcrops.
•Macro-catchmentwaterharvesting,alsocalledharvestingfromexternal
catchmentsisthecasewhererunofffromhill-slopecatchmentsisconveyedtothe
croppingarealocatedatfoothillonflatterrain.
JNKVV
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College of Agriculture,
Powarkheda

6. 2.FloodWaterHarvesting
Floodwaterharvestingcanbedefinedasthecollectionand
storageofcreekflowforirrigationuse.Floodwater
harvesting,alsoknownas‘largecatchmentwater
harvesting’or‘SpateIrrigation’,maybeclassifiedinto
followingtwoforms:
I.Incaseof‘floodwaterharvestingwithinstreambed’,
thewaterflowisdammedandasaresult,inundates
thevalleybottomofthefloodplain.Thewateris
forcedtoinfiltrateandthewettedareacanbeusedfor
agricultureorpastureimprovement.
II.Incaseof‘floodwaterdiversion’,thewadiwateris
forcedtoleaveitsnaturalcourseandconveyedto
nearbycroppingfields.
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7. 3. Groundwater Harvesting
•Groundwaterharvestingisarathernewtermandemployedto
covertraditionalaswellasunconventionalwaysofgroundwater
extraction.
•Qanatsystems,undergrounddamsandspecialtypesofwellsarea
fewexamplesofthegroundwaterharvestingtechniques.
•Groundwaterdamslike‘SubsurfaceDams’and‘SandStorage
Dams’areotherfineexamplesofgroundwaterharvesting.
•Theyobstructtheflowofephemeralstreamsinariverbed;the
waterisstoredinthesedimentbelowgroundsurfaceandcanbe
usedforaquiferrecharge.
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8. Water harvesting Technique
Runoff Harvesting
Short Term
Contour Bund
Semi-circular
Hoop
Trapezoidal
Bund
Graded Bunds
Rock
Catchment
Ground
Catchment
Long Term
Dugout Pond
Farm Ponds
Irrigation Dam
Silt detention Dam
High level Pond
Percolation Dam
Flood Water Harvesting
Permeable Rock Dam
Water Spreading Bunds
Flood Control Reservoir
Groundwater Harvesting
Qanat System

9. Runoff Harvesting
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10. 10
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College of Agriculture, Powarkheda
Runoffharvestingforshortandlongtermisdonebyconstructingstructuresas
givenbelow.
Short Term Runoff Harvesting Techniques
1.Contour Bunds
2.Semi-circular Hoop
3.Trapezoidal Bunds
4.Graded Bunds
5.Rock Catchment
6.Ground Catchment

11. Contour Bunds
•Thismethodinvolvesthe
constructionofbundsonthe
contourofthecatchmentarea.
•Thesebundsholdtheflowing
surfacerunoffinthearea
locatedbetweentwoadjacent
bunds.
•Theheightofcontourbund
generallyrangesfrom0.30to
1.0mandlengthfrom10toa
few100meters.
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12. Semicircular Hoop
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13. Semicircular Hoop
•Thistypeofstructureconsistsofanearthenimpartmentconstructedintheshapeofa
semicircle.
•Thetipsofthesemicircularhooparefurnishedonthecontour.
•Thewatercontributedfromtheareaiscollectedwithinthehooptoamaximumdepth
equaltotheheightoftheembankment.
•Excesswaterisdischargedfromthepointaroundthetipstothenextlowerhoop.
•Therowsofsemicircularhoopsarearrangedinastaggeredformsothattheover
flowingwaterfromtheupperrowcanbeeasilyinterruptedbythelowerrow.
•Theheightofhoopiskeptfrom0.1to0.5mandradiusvariesfrom5to30m.
•Suchtypeofstructureismostlyusedforirrigationofgrasses,fodder,shrubs,treesetc.
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14. Trapezoidal Bunds
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15. Trapezoidal Bunds
•Suchbundsalsoconsistofanearthenembankment,constructedintheshapeoftrapezoids.
•Thetipsofthebundwingsareplacedonthecontour.
•Therunoffwateryieldedfromthewatershediscollectedintothecoveredarea.
•Theexcesswateroverflowsaroundthetips.Inthissystemofwaterharvestingtherowsof
bundsarealsoarrangedinstaggeredformtointercepttheoverflowofwaterfromthe
adjacentupstreamareas.
•Thelayoutofthetrapezoidalbundsisthesameasthesemicircularhoops,butthey
unusuallycoveralargerarea.
•Trapezoidalbundtechniqueissuitablefortheareaswheretherainfallintensityistoohigh
andcauseslargesurfaceflowtodamagethecontourbunds.
•Thistechniqueofwaterharvestingiswidelyusedforirrigatingcrops,grasses,treesetc.
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16. Graded Bunds

17. Graded Bunds
Gradedbundsalsoreferredasoffcontourbunds.
Theyconsistofearthenorstoneembankmentsandareconstructedonalandwith
asloperangeof0.5to2%.
Thedesignandconstructionofgradedbundsaredifferentfromthecontourbunds.
Theyareusedasanoptionwhererainfallintensityandsoilsaresuchthatthe
runoffwaterdischargedfromthefieldcanbeeasilyintercepted.
Theexcessinterceptedorharvestedwaterisdivertedtothenextfieldthougha
channelranges.
Theheightofthegradedbundrangesfrom0.3to0.6m.
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18. JNKVV-College of Agriculture, Powarkheda 18Rock Catchment

19. JNKVV-College of Agriculture, Powarkheda 19
Rock Catchment

20. Rock Catchment
•Therockcatchmentsaretheexposedrocksurfaces,usedfor
collectingtherunoffwaterinapartasdepressedarea.
•Thewaterharvestingunderthismethodcanbeexplainedas:when
rainfalloccursontheexposedrocksurface,runofftakesplacevery
rapidlybecausethereisverylittleloss.
•Therunoffsoformedisdrainedtowardsthelowestpointcalled
storagetankandtheharvestedwaterisstoredthere.Theareaof
rockcatchmentmayvaryfroma100m
2
tofew1000m
2
;accordingly
thedimensionsofthestoragetankshouldalsobedesigned.
•Thewatercollectedinthetankcanbeusedfordomesticuseor
irrigationpurposes.
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College of Agriculture,
Powarkheda

21. JNKVV-College of Agriculture, Powarkheda 21
Ground Catchment

22. Ground Catchment
•Inthismethod,alargeareaofgroundisusedascatchmentforrunoffyield.
•Therunoffisdivertedintoastoragetankwhereitisstored.
•Thegroundisclearedfromvegetationandcompactedverywell.
•Thechannelsareaswellcompactedtoreducetheseepageorpercolationlossand
sometimestheyarealsocoveredwithgravel.
•Groundcatchmentsarealsocalledroadedcatchments.
•Thisprocessisalsocalledrunoffinducement.
•Groundcatchmentshavealsobeentraditionallyusedsincelast4000yearsinthe
Negev(adesertinsouthernIsrael)whereannulcropsandsomedroughttolerant
specieslikepistachiodependentonsuchharvestedwateraregrown.
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23. Long Term Runoff Harvesting Techniques

24. Long Term Runoff Harvesting Techniques
Thelongtermrunoffharvestingisdoneforbuildingalargewaterstorageforthepurposeof
irrigation,fishfarming,electricitygenerationetc.Itisdonebyconstructingreservoirsand
bigpondsinthearea.
The design criteria of these constructions are given below.
1.Watershed should contribute a sufficient amount of runoff.
2.There should be suitable collection site, where water can be safely stored.
3.Appropriate techniques should be used for minimizing various types of water losses
such as seepage and evaporation during storage and its subsequent use in the watershed.
4.There should also be some suitable methods for efficient utilization of the harvested
water for maximizing crop yield per unit volume of available water.
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College of Agriculture,
Powarkheda
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25. Long Term Runoff Harvesting
Structures
1.Dugout Ponds
2.Farm Pond
3.High Level Pond
4.Irrigation Dam
5.Silt DetensionDam
6.Percolation Dam
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26. Dugout Pond
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27. Dugout Ponds
•Thedugoutpondsareconstructedbyexcavatingthesoilfromthegroundsurface.
•Thesepondsmaybefedbygroundwaterorsurfacerunofforbyboth.
•Constructionofthesepondsislimitedtothoseareaswhichhavelandslopelessthan
4%andwherewatertablelieswithin1.5-2metersdepthfromthegroundsurface.
•Dugoutpondsinvolvemoreconstructioncost,thereforethesearegenerally
recommendedwhenembankmenttypepondsarenoteconomicallyfeasible.
•Dugoutpondscanalsoberecommendedwheremaximumutilizationoftheharvested
runoffwaterispossibleforincreasingtheproductionofsomeimportantcrops.
•Thistypeofpondsrequirebrickliningwithcementplasteringtoensuremaximum
storagebyreducingtheseepageloss.
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28. Irrigation Dam
•Theirrigationdamsaremainlymeant
tostorethesurfacewaterforirrigating
thecrops.
•Thecapacityisdecidedbasedonthe
amountofinputwateravailableand
outputwaterdesired.
•Thesedamshavetheprovisionsof
gatedpipespillwayfortakingoutthe
waterfromthereservoir.
•Spillwayislocatedatthebottomofthe
damleavingsomeminimumdead
storagebelowit.
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29. 29
Silt Detention Dam
JNKVV-College of Agriculture, Powarkheda

30. Silt Detention Dam
•The basic purpose of silt detention dam is to detain the silt load coming along with the
runoff water from the catchment area and simultaneously to harvest water.
•The silt laden water is stored in the depressed part of the catchment where the silt
deposition takes place and comparatively silt free water is diverted for use.
•Such dams are located at the lower reaches of the catchment where water enters the valley
and finally released into the streams.
•In this type of dam, provision of outlet is made for taking out the water for irrigation
purposes.
•For better result a series of such dams can be constructed along the slope of the catchment.
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31. High Level Pond

32. High Level Pond
•Suchdamsarelocatedattheheadofthevalleyto
formtheshapeofawatertankorpond.
•Thestoredwaterinthepondisusedtoirrigatethe
arealyingdownstream.Usually,forbetterresulta
seriesofpondscanbeconstructedinsuchaway
thatthecommandareaofthetanklocated
upstreamformsthecatchmentareaforthe
downstreamtank.
•Thusallbuttheuppermosttanksarefacilitatedwith
thecollectionofrunoffandexcessirrigationwater
fromtheadjacenthighercatchmentarea.
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33. Farm Pond
•Farmpondsareconstructedformulti-
purposeobjectives,suchasfor
irrigation,live-stock,watersupplyto
thecattlefeed,fishproductionetc.
•Thepondshouldhaveadequate
capacitytomeetalltherequirements.
•Thelocationoffarmpondshouldbe
suchthatallrequirementsareeasily
andconvenientlymet.
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34. •Thefarmpondscanbeconsideredaswater
harvestingponds.
•Theymaybedugoutorembankmenttype.
•Theircapacitydependsuponthesizeof
catchmentarea.
•Runoffyieldfromthecatchmentisdiverted
intotheseponds,whereitisproperly
stored.
•Measuresagainstseepageandevaporation
lossesfromthesepondsshouldalsobe.
Water Harvesting Pond

35. Percolation Dam
•Thesedams aregenerally
constructedatthevalleyhead,
withouttheprovisionofchecking
thepercolationloss.
•Thus,alargeportionoftherunoffis
storedinthesoil.
•Thegrowingcropsondownstream
sideofthedam,receivethe
percolatedwaterfortheirgrowth.
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36. Flood Water Harvesting
1.PermeableRockDams
2.WaterSpreadingBunds
3.FloodControlReservoir
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37. Flood Water Harvesting
•Toharvestfloodwater,widevalleysarereshapedandformed
intoaseriesofbroadlevelterracesandthefloodwateris
allowedtoenterintothem.
•Thefloodwaterisspreadontheseterraceswheresomeamount
ofitisabsorbedbythesoilwhichisusedlateronbythecrops
growninthearea.
•Therefore,itisoftenreferredtoas"WaterSpreading"and
sometimes"SpateIrrigation".
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38. 38
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The main characteristics of water spreading are:
•Turbulent channel flow is harvested either by diversion or by spreading within
the channel bed/valley floor.
•Runoff is stored in soil profile.
•It has usually a long catchment (may be several km)
•The ratio between catchment to cultivated area lies above 10:1.
•It has provision for overflow of excess water.

39. Permeable Rock Dams
•Thesearelonglowrockdamsacross
valleysslowingandspreading
floodwateraswellashealinggullies.
•Thesearesuitableforasituation
wheregentlyslopingvalleysare
likelytotransformintogulliesand
betterwaterspreadingisrequired.
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40. Water Spreading Bunds
•In this method, runoff water is diverted to the area
covered by graded bund by constructing diversion
structures such as diversion drains.
•They lead to the basin through channels, where crops
are irrigated by flooding.
•Earthen bunds are set at a gradient, with a "dogleg"
shape and helps in spreading diverted floodwater.
•These are constructed in arid areas where water is
diverted from watercourse onto crop or fodder block.
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41. Flood Control Reservoir
•Thereservoirsconstructedat
suitablesitesforcontrollingthe
floodareknownasfloodcontrol
reservoirs.
•Theyarewellequippedwithself-
operatingmechanicaloutletsfor
lettingouttheharvestedwaterinto
thestreamorcanalbelowthe
reservoirasperrequirement.
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42. General Allocation of Storage in a Reservoir
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43. Groundwater Harvesting
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44. JNKVV-College of Agriculture, Powarkheda
44
Cross Section Showing Qanats Ariel view of Qanats.
Qanat System

45. Qanat System
•Aqanatconsistsofalongtunnelorconduitleadingfromawelldugatareliable
sourceofgroundwater(themotherwell).
•Often,themotherwellisdugatthebaseofahillorinthefoothillsofamountain
range.
•Thetunnelleadingfromthemotherwellslopesgraduallydownwardtocommunities
inthevalleybelow.
•Accessshaftsaredugintermittentlyalongthehorizontalconduittoallowfor
constructionandmaintenanceoftheqanat.
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46. •TheQanatsystemwasusedwidelyacrossPersiaandtheMiddleEastformany
reasons.
•First,thesystemrequiresnoenergy,reliesontheforceofgravityalone.
•Second,thesystemcancarrywateracrosslongdistancesthroughsubterranean
chambersavoidingleakage,evaporation,orpollution.
•Andlastly,thedischargeisfixedbynature,producingonlytheamountofwaterthat
isdistributednaturallyfromaspringormountain,ensuringthatthewatertableis
notdepleted.
•Moreimportantly,itallowsaccesstoareliableandplentifulsourceofwatertothose
livinginotherwisemarginallandscapes.
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47. Roof Top Rain
Water
Harvesting
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48. 48
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Roof Top Rain Water Harvesting
•RooftopRainWaterHarvestingisthetechniquethroughwhichrain
wateriscapturedfromtheroofcatchmentsandstoredinreservoirs.
•Harvestedrainwatercanbestoredinsub-surfacegroundwater
reservoirbyadoptingartificialrechargetechniquestomeetthe
householdneedsthroughstorageintanks.
•TheMainObjectiveofrooftoprainwaterharvestingistomakewater
availableforfutureuse.
•Capturingandstoringrainwaterforuseisparticularlyimportantin
dryland,hilly,urbanandcoastalareas.
•Inalluvialareasenergysavingfor1m.riseingroundwaterlevelis
around0.40kilowattperhour.

49. Need for Rooftop Rain-Water Harvesting
1.To meet the ever-increasing demand for water.
2.To reduce the runoff which chokes storm drains.
3.To avoid flooding of roads.
4.To reduce ground water pollution.
5.To improve the quality of ground water.
6.To reduce the soil erosion.
7.To augment the ground water storage and control
decline of water levels.
8.To supplement domestic water requirement
during summer, drought etc.
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50. 50
Advantages of Rain Water Harvesting
1.Providesself-sufficiencytoyourwatersupply.
2.Reducesthecostforpumpingofgroundwater.
3.Provideshighqualitywater,softandlowin
minerals.
4.Improvesthequalityofgroundwaterthrough
dilutionwhenrechargedtogroundwater.
5.Reducessoilerosioninurbanareas.
6.Rooftoprainwaterharvestingislessexpensive.
7.Rainwaterharvestingsystemsaresimple
whichcanbeadoptedbyindividuals.

51. 8.Rooftoprainwaterharvestingsystemsareeasytoconstruct,
operateandmaintain.
9.Inhillyterrains,rainwaterharvestingispreferred.
10.Insalineorcoastalareas,rainwaterprovidesgoodqualitywater
andwhenrechargedtogroundwater,itreducessalinityandalso
helpsinmaintainingbalancebetweenthefresh-salinewater
interface.
11.InIslands,duetolimitedextentoffreshwateraquifers,rainwater
harvestingisthemostpreferredsourceofwaterfordomesticuse.
12.Indesert,whererainfallislow,rainwaterharvestinghasbeen
providingrelieftopeople.
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52. Safety Consideration
StorageinGroundWaterReservoir
1.Forrooftoprainwaterharvestingthrough
existingtubewellsandhandpumps,filteror
desiltingpitshouldbeprovidedsothatthewells
arenotsilted.
2.Suchtubewellsifpumpedintermittently,
increasetheefficiencyofrecharge.
3.Ifthegroundwaterreservoirisrecharged
through,shaft,dugwelletc.,invertedfiltermay
beprovided.
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53. Storage in Tanks
1.storagetankshouldnotbelocatedclosetoasourceofcontamination,suchasaseptictanketc.
2.Astoragetankmustbelocatedonalowerlevelthantherooftoensurethatitfillscompletely.
3.Arainwatersystemmustincludeinstallationofanoverflowpipewhichemptiesintoanon-flooding
area.Excesswatermayalsobeusedforrechargingtheaquiferthroughdugwellorabandoned
handpumportubewelletc.
4.Aspeedbreakerplatemustbeprovidedbelowinletpipeinthefiltersoasnottodisturbthe
filteringmaterial.
5.Storagetanksshouldbeaccessibleforcleaning.
6.TheinletintotheStoragetankshouldbescreenedinsuchwaythatthesecanbecleanedregularly.
7.Watermaybedisinfectedregularlybeforeusingfordrinkingpurposebychlorinationorboilingetc.
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54. Components of Roof Top Rain
Water Harvesting system
1.Catchment
2.Transportation (Gutter, Pipe,
Fittings)
3.First Flush System
4.Filter
5.Storage Facility
6.Recharge Facility
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55. 55
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1.Catchment
•Thesurfacethatreceivesrainfalldirectlyisthecatchmentofrainwater
harvestingsystem.
•Itmaybeaterrace,courtyard,orpavedorunpavedopenground.
•TheterracemaybeaflatRCC/stonerooforslopingroof.
•Thereforethecatchmentisthearea,whichactuallycontributesrainwaterto
theharvestingsystem.

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2. Transportation
•Rainwaterfromtherooftopshouldbecarriedthroughdowntotakewater
pipesordrainstothestorage/harvestingsystem.
•WaterpipesshouldbeUVresistant(ISIHDPE/PVCpipes)oftherequired
capacity.
•Waterfromslopingroofscouldbecaughtthroughguttersanddowntakethe
pipe.
•Atterraces,themouthofeachdrainshouldhavewiremeshtorestrictfloating
material.

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3. First Flush
•Thefirstflushisadeviceusedtoflushoffthewaterreceivedinthefirstshower.
•Thefirstshowerofrainsneedstobeflushed-offtoavoidcontaminating
storable/rechargeablewaterbytheprobablecontaminantsoftheatmosphere
andthecatchmentroof.
•Itwillalsohelpincleaningofsiltandothermaterialdepositedontheroofduring
dryseasons.
•Provisionsoffirstrainseparatorsshouldbemadeattheoutletofeachdrainpipe.

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4.Filters
•Filtersareusedforthetreatmentofwatertoeffectivelyremoveturbidity,color,and
microorganisms.
•Afterthefirstflushingofrainfall,watershouldpassthroughfilters.
•Agravel,sand,and‘netlon’meshfilterisdesignedandplacedontopofthestorage
tank.
•Thisfilterisveryimportantinkeepingtherainwaterinthestoragetankclean.
•Itremovessilt,dust,leaves,andotherorganicmatterfromenteringthestorage
tank.

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5. Storage facility
•There are various options available for the construction of these tanks with respect
to the shape, size, material of construction and the position of tank and they are: -
Shape : Cylindrical, square and rectangular.

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6.RechargeStructures
•RainwaterHarvestedcanalsobeusedforchargingthegroundwateraquifers
throughsuitablestructureslikedugwells,borewells,rechargetrenchesandrecharge
pits.
•Variousrechargestructuresarepossible–somewhichpromotethepercolationof
waterthroughsoilstrataatshallowerdepth(e.g.,rechargetrenches,permeable
pavements)whereasothersconductwatertogreaterdepthsfromwhereitjoinsthe
groundwater(e.g.rechargewells).

61. Precautions
1.The roof or terraces used for harvesting should be clean.
2.Do not store chemicals, rusting iron, manure or detergent on the roof.
3.Avoid using terraces for toilet by you and your pets.
4.Provide gratings at mouth of each drainpipe on terraces to trap
debris and floating materials.
5.Prevent storage system from contamination.
6.Provision of first rain separator should be made to flush first rain.
7.Do not use polluted water to recharge ground water.
8.Before recharging arrangements of filtering should be provided
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62. Thanks for listening…..
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