Sources of water

civil engineering,civil,irrigation,environmental

1. Sources of water
•ThevarioussourcesofwateravailableforpotablewaterareclassifiedasSurfaceandunderground
•Surfacewatersourcesconsistsof;RiversandStreams;Pondsandlakes,Reservoirsandoceanswhile,
Subsurfacewatersourcesaresprings,infiltrationwells,andtubewells.
•Surfacesourcesofwatersupply:Surfacesourcesofwaterarereadilyavailableforwatersupply.These
sourcesare(i)NaturalpondsandLakes;(ii)StreamsandRivers;and(iii)Reservoirs.
PondsandLakes:Anaturallargesizeddepressionformedwithinthesurfaceoftheearth,whengetsfilled
withwaterispondorLake.Whenthedepressionissmallispond,whilelargesizeislake.Thesourceof
wateristhecatchmentareatowhichthestreamsordrainscontribute.Sometimestheundergroundwater
throughspringsentersintoit.Thequantityofwaterfromsuchsourcesdependsoncatchmentarea,
rainfallandgeologicalformation.Suchsourceofwaterisusefulforsmallcommunitylikevillagesortown.
TheQualityofsuchsourceisgenerallygoodanddoesnotneedproperpurification.Naturalpurificationof
waterduetosedimentationofsuspendedmatter,removalofbacteriaandbleachingofcolorfurther
purifywater.Theproblemofalgae,weedandvegetablegrowthtakeplace,impartingbadsmells,tasteand
colorstotheirwaters.
StreamsandRivers:smallstreamschannelsfeedthewatertolakesandrivers.Suchsourceofwaterisnot
reliableforwatersupplyasoflessquantityandsometimesdry.Theyareusefulforsmallcommunity.
Largerandperennialstreamsmayhoweverbeusedasasourcesofwatersupply.Riversaretheimportant
sourceofwatersupplyschemes.Perennialriverscanbeusedassourcesofpublicsuppliesbyproviding
storageontheupstreamoftheintakeworks.Onnonperennialriversdamshastobeconstructed.

2. •The water quality of rivers is not reliable as it contains large amount of silt, sand and other suspended
matters. The disposal of untreated sewage further contaminate water. The river water must therefore be
properly analyzed and well treated before supplying to the community.
•Reservoirs:Awatersupplyschemeusingriverorstreamwaterdirectlymaynotsatisfytheconsumer
demandduringlowflow,whileahighflowsitisdifficulttowithdrawwaterduetofloodsituation.A
barrierthereforebeconstructedacrosstheriversoastoformapoolofwaterontheupstreamsideofthe
barrier.Thispoolisknownasstoragereservoir.Thestoredwatercannotbeusedonlyforwatersupplybut
alsoforotherpurposesaswell.Thequalityofsuchreservoirsislikealake.
•Surfacewatersuppliesareclassifiedastowhethertheycomefromalake,reservoirorriver.Generallya
riverhasthelowestwaterqualityandareservoirthehighest.Riverwaterisqualityislargelyinfluencedby
pointsourcepollutionlikemunicipalities,industriesandnonpointsourcepollutionlikeagricultural
practices.Duringrainsorperiodofrunoffofturbidityincreases,makingwatermorepolluted.Someofthe
riverwaterhavecolor,tasteandinodorproducingcompounds.
•Reservoirandlakesourceshavemuchlessdaytodayvariationthanrivers.Alsothequiescentconditions
willreducebothturbidityandcolor.
Sub surface or underground sources: The water which store in the ground water reservoir through
infiltration is under ground water. This water is generally uncontaminated but may contain aesthetically or
economically undesirable impurities. Such water are rich in dissolved salts, minerals and various gasses.
Ground water may be classified as

3. 3
Ground
water
Surface water
Shallow Well Deep well
Lake Reservoir River or stream
General characteristics of ground water and surface water
Ground water Surface water
Constant composition Varying composition
High mineralization Low mineralization
Little turbidity High Turbidity
Bacterial safe Microorganisms present
No dissolved oxygen Dissolved oxygen
High hardness low hardness

4. (i)Shallow Well and (ii) Deep well
•Groundwaterisclassifiedasdeeporshallowwells.Deepwellsusuallyhavehighconcentrationofiron,
calcium,magnesium,manganese,carbonateandotherminerals.Shallowwellsarerechargedbyanearby
surfacewatersources.ItmayhavequalitiessimilartothedeepwellsorofthecharacteristicsofSurface
water.Strataofsubsoilactasfilterandremovethesuspendedimpuritiesaswaterinfiltratedintothesoil.
•SelectionofSourceofWater:
Whenselectingasourceofwatersupplythefollowingpointsconsiderationisessential
Quantity:Thequantityofwateravailableatthesourcemustbesufficienttomeetthedemandsduringthe
entiredesignperiodofscheme.
Quality:Theavailablewatermustnotbetoxicorotherinjurioustohealth.Theimpuritypresentinwater
mustbeaslessaspossibleandshouldbeeasilyremovablebytreatment.
Distanceofsourcesupply:Thesourceofwatermustbesituatedasnearthecityaspossible.Itreducethe
costofpipelinesaswellasotherappurtenancesasrequiredfordistributionofwaterforconsumption.
Topographyofthearea:Theareabetweenthesourceandthecityshouldnothavemoredepressionsand
elevation.Insuchuneventopographies,thecostforconveyanceofwaterbypipesorconstructingof
tunnelsincreasethecostofwatersupplyschemes.
Elevationofsourceofsupply:Thesourceofwatermustbeonhighcontour,soastoflowwaterbygravity.
Whenthewaterisavailableatlowelevationthanthecitylevel,pumpinghastobeused,whichinvolves
hugeexpenditureandpossiblebreakdown.

5. Water supply for Rural Area
•More than 60% of Population living in rural area where a high percentage of population having no access
to piped potable water. It is not feasible to cover all villages with potable water supplies because of;
•Scattered and inaccessible nature of villages;
•Non availability of nearby water sources;
•Non availability of adequate funds to take up those projects which may serve few people, and hence may
not become financially viable.
On the basis of these constraints, it is difficult to supply piped potable water to the villages through a full
fledged conventional water treatment plant, and hence special simple methods are adopted to treat the
available water supplies in rural areas.
Most of our villages depend upon the ground water supplies to be extracted through wells and tube wells.
In hilly areas natural springs also available. The nature of treatment depend upon the quality of water
source available. The river and stream water containing low concentration of dissolved salts, high organic
and inorganic pollutants, and turbidity. Such water is generally not fit for drinking purposes without proper
treatment. The Lakes water are comparatively clean in those areas where industrial and urban sewage are
not discharges directly into it. Some times the growth of algae affect the quality of water and make it unfit
for drinking purposes. Springs are natural sources of ground water and is normally clean water which can
be used for drinking purposes. Proper protection of the site of spring from defecation and drainage is
important to avoid its contamination. Such sources of water can be used for community without pumping
at minimum cost and maintenance.

6. Rain Water Harvesting
•Rainwaterharvestingisthecollectionofrainwaterfromtheroofsandpavedcourtyardsofhouseseither
instoragetanksorinthegroundwaterreservoir.Thecollectedwaterservesasapropersourceof
drinkingwaterinruralareasorinsuchareaswherehighrainfalloccurs.Thistechniquecanalsobeusedin
urbanareaswheremorerainfalloccurs,andothersourcesofwaterisscare,whilethegroundwaterlevels
havegonedown.Initssimplestformtheroofwateristakingdownthroughapipefromtheroofoutletto
thegroundfloor,whichcanbeconnectedtoawatertank.Therainwaterbeforecollectionshouldbe
passedthroughaporousmedialikesandorcharcoalfilterforremovalofsuspendedparticlesand
microorganismsthatgainedduetorunoff.Thesandorsandandcharcoallayersareusuallyfollowedby
gravellayers.Inthiswaytwotothreelayersofsandandgravelarearranged.Similarly,thesefiltersmust
becleanedperiodicallytopreventcloggingofitspores.Theroofmustalsobeascleanedaspossibleatthe
timeofrainfall.Thesandfiltersmustbeperiodicallycleanedtopreventcloggingofitspores.
•RainwatercollectionforDirectUse.Therainwaterfordirectusecanbecollectedfromtheroofintoa
storagetankofplastic.RCCormasonry.Thetankcanbeplacedeitheraboveorbelowtheground
dependingontheavailabilityofspace.Thefiltermustbecleanedanddisinfectantregularly.Where
sufficientspaceisavailable,thewatercanbestoredinanopenexcavatedpond,whichactsasasettling
pondforimpurity.Similarly,ifthedirectuseofharvestedwaterisnotpossiblethensuchwatercanbe
usedtorechargethegroundwater.Forsuchactivityeithertherainwaterisdirectingtoinfiltrateintothe
groundtoimprovethewatertableorthrougharechargepitorwell,dependingupontheavailable
opportunities.

7. •Selection of suitable source of water for Rural Areas: When more than one possible source of water is
available, the choice should be made in order of the following priorities
(i) reliability of the source
(ii) Purity of the water available in the source; and
(iii) The ease with which the water from the source can be supplied to the consumers.
Ifwatersupplyisplannedfromanunexploitedsource,laboratorytestsareessentialtoknowthelevelof
impurityandtheneedoftreatment.Multiplesamplestakenoveraperiodoftimewillprovidemore
informationthanasinglesample.Samplesshouldbeanalyzedsoonaftercollectionassomebiologicaland
chemicalchangesoccurswithtime.Theparameterstobetestedforagivenwatersourceisdependonthe
typeofwatersource.LikeforsurfacewaterandshallowwellsBOD,Chlorinedemandandammoniatestis
required.Fordeepwellsthehardness,pHvalue,dissolvedmetalslikelead,iron,fluoride,arsenicand
nitratestestsarerequired.
•WaterTreatmentMethodsForRuralSuppliesORAppropriatetechnologyforwatersupply.Thewater
treatmentforruralareaandsmallcommunitydependsonthequalityofrawwater,andtheavailabilityof
allocatedfundstomeetthecostoftreatmentaswellastheoperationandmaintenance.Theallocated
fundsforruralareasareusuallyscareandnotsufficienttomeetthecostofconventionaltreatmentplant.
Majorityofwatersupplyinruralareasarefromwellsandtubewellsthequalityofwhichisacceptable.In
someareajustchlorinationhastobedonetoeliminatebacterialcontaminationifpresentinwatersupply.
Whentubewellareusedforwatersupply,thensomechemicaltestslikenitrates,fluorideiron,
manganesetestsarerequired.

8. •ExcessnitratesareusuallyfoundastheendproductofbiodegradationofHumanandAnimalexcreta.If
concentrationofnitratesarehigh,thenalternatesourcemaybeconsidered.Ifalternatesourceisnot
availablethenevenhighconcentrationofNitratescontainingwaterbeused.
•ExcessiveFluorideindrinkingwatercausedfluorosis