ASSESSING THE POTENTIALITY OF RAINWATER HARVESTING VIA ZONING IN THE CORECITY LIMITS OF THE KATHMANDU METROPOLITANCITY

Abstract

Rapidandhaphazardurbanization,alarmingpopulationgrowth,andclimatechange arecausingahugestressinwatermanagementinKathmanduMetropolitanCity(KMC). Withoutproperalternativesourceofwatersupply,andthetimeandagainfailureofMelam­ chiwaterSupplyProject,thedemandandsupplygapiscontinuouslyexpandinginthe Valley,andinKMC.Overexploitationofgroundwaterwithamotivetomeetthedemand ofwaterhascausedagreatdeclineingroundwaterlevel.But,notjustthewaterscarcity monsoonfloodinginthevalleyhasalsobecometopicofconcernbecauseofincreasedin­ tensityandfrequencyofurbanfloodinginthecityaffectingdailylivelihoodofthepeople andalsocausingahugehuman,financial,andphysicaldamagehere.Rainwaterharvest­ ing(RWH)isconsideredasapotentialsolutioninaddressingwaterstressandaidingwater managementindifferentpartsoftheworld.So,thisstudyiscarriedouttoassessthepo­ tentialofRainwaterHarvestinginurbancontextofKMCandthepotentialrunoffvolume thatcouldbeharvested. Studydelineatesthe RainwaterHarvestingPotetialityIndex via zoning within KMC. Analyticalhierarchyprocess(AHP)basedmulti­criteriadecisionmakingisappliedes­ tablishingrainwaterharvestingpotentialityindex(RWHPI).Thestudyalsorequiredhy­ drologicalmodellingofbasinofthestudyareainrainfall­runoffsimulationtoestimate therunoffcoefficientofthesub­basins.Drainagedensity,roofareadensity,basinslope, andrunoffcoefficientareconsideredforassessingRWHPI.Resultsshowedthat28.78% ofthetotalbasinareahasgoodRWHPI,46.30%hasmoderate,andonly24.90%haslow RWHPI.Also,RoofRainwaterharvesting(R­RWH)isaloneabletomeetnearly23%of thetotaldomesticwaterdemandofthecity.