rainwater harvesting in mumbai

8/10/2019 Rainwater Harvesting in Mumbai

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Rain Water Harvesting in Mumbai, India: Application of GIS

Prakas M Apte

!rban "evelopment #onsultant

Abstract:

Surface $ater is inade%uate to meet demands of our urban centres& Wile infiltration ofrain $ater into te sub'soil as decreased, pressure of population gro$t andindustriali(ation as accelerated te rate of dra$ing underground $ater in e)cess of terate at $ic te $ater table gets recarged b* natural means& Rain $ater arvesting ismerel* +putting back rain $ater into te soil, $ere it $ill be stored in undergroundreservoirs and ac%uifers& We need a rain $ater arvesting s*stem tat is sustainable,replicable and economicall* viable& In densel* populated urban centres like Mumbai inIndia, rain$ater arvesting is no$ being pursued in order to reconcile demand andsuppl*& It affords an opportunit* for e%uitable, efficient and sustainable use of $aterresources & Practical e)perience in te past as establised te socio'economic impactsof rain $ater arvesting at plot scale& If it is promoted at te cit* scale and gains $ideracceptance, te associated social, economic, and environmental benefits $ill contribute

substantiall* in improving te %ualit* of life in Mumbai& -e paper e)amines te role ofGIS in promoting a s*stem and metodolog* for rain $ater arvesting and datare%uirements to enable its large scale adoption in Mumbai&

.e*$ordsRain $ater arvesting, Geograpical Information S*stem/GIS0

Mumbai, #apital of Maarastra State& India&

Population 12&31million /estimated0 in 2445&

Area 567 S%&.m&/ Municipal #orporation of Greater Mumbai limits0

#ostal 8engt 154 km&

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Mumbai, over te last fe$ decades, as emerged as te financial and commercial capitalof India& !rban gro$t as spread be*ond te boundaries2of te Municipal #orporation&

Geolog* and Geomorpolog* of Mumbai:

-e Greater Mumbai area is made up of te "eccan basalt, ori(ontall* bedded and moreor less uniform in caracter over $ide areas&-e predominant soil cover in te island cit*is sand* $ereas in te suburban areas, it is alluvial and loam*&

Greater Mumbai receives rains from sout'$est monsoons, $ic commence usuall* inte first fortnigt of 9une and last till te end of September& Pre'monsoon so$ers occurin Ma* and occasionall*, nort'east monsoon so$ers in ctober and ;ovember& -eaverage annual rainfall is 254&5 mm 0 -e average montl* rainfall in 9une is>5=&< mm& and 643&2 mm& in September&

-e climate of Mumbai is tropical& -e dail* ma)imum temperature /mean0 ranges from66&6 c in Ma* to 23&1 #& in August& "ail* minimum temperature /mean0 rage from 1>&6 #&in9anuar* to 2>&2 #& in Ma*&

Water Suppl*

"aiser and Miti are te t$o rivers in Greater Mumbai, te first originates at .anericaves and meets Gorai creek and te second originates at ?iar lake and meets Maimcreek& ver flo$ of ?iar, -ulsi and Po$ai lakes goes to Miti River&

-ere are tree ma@or lakes /?iar,-ulsi Po$ai' see map on page 60 $itin te cit* tatsuppl* $ater to te Metropolis&

;ame of te 8ake -ulsi ?iar Po$ai

8ocation;ational Park areabet$een Mulund Borivali i&

;ear ;I-ICBandup

Bet$een ?ikroli andBandup ;ear I& I& -& Po$ai

#apacit* of te 8akein M # M

14&51< M#M 51&=>> M#M M#M

#atcment area ins%& km&

>&=4 s%&km& 17&34 s%&k&m& >&>7 s%& k&m&

Mumbai receives its $ater suppl* from tese lakes and also from oter lakes located in-ane district& -e suppl* from all tese sources is o$ever inade%uate 5 to service tepopulation of Mumbai& Against a standard laid do$n b* te Municipal #orporation /in itso$n regulations0 of suppl* of 16< liters of potable $ater per capita per da*, te actualsuppl* is less tan 34 l&p&c&p&d& for te 54D of MumbaiEs population residing in EformalEousing& For 64 liters per capita per da*& -e balance of 2


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-e $atersuppl* facilities and utilities in Greater Mumbai6if mapped on GIS application$ould elp planners, administrators, emergenc* services and utilit* providers&

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In tis paper, I propose evolving a metodolog* tat can utili(e Geograpic InformationS*stem /GIS0 and empirical data for anal*(ing spatial $ater arvesting patterns $it teob@ective of prioriti(ing undertaking $aterarvesting pilot pro@ects in te cit* of Mumbai&

!rban $ater Suppl* strateg*:

-ere is an increasing a$areness tat $ater resources in Mumbai are being stretced toteir limits resulting in available suppl* var*ing considerabl* during te course of a *ear&It is necessar* terefore to find $a*s of saving, reusing and rec*cling $ater and todevelop metodologies to improve $ater resource management to ensure a stable suppl*of $ater trougout te *ear& Water resources management strategies traditionall*focused on suppl*'side5policies& Instead, tere as to be a movement to$ards demand'control policies to meet gro$ing needs& -e emergence of te goals of sustainable $atermanagement necessiate te development of constructive applications of ne$tecnologies like GIS to address tese issues& -e Strateg* sould be:

"emand #ontrol

ptimi(ation of e)isting suppl*

#onservation of natural resources

Rain $ater arvesting troug p*sical storage

Rain $ater arvesting b* recarging underground a%uifers

measures to facilitate ma)imum percolation of rain$ater in te ground

Identification and mapping of a%uifers ' Municipal $ard$ise

Identification and mapping of underground streams and losses troug draining

off to te sea and saliniation Priorati(ation of Municipal $ards for taking up pilot rain arvesting pro@ects

"emand #ontrol Policies:

"emand control policies, re%uire tat te $ater suppl* agenc* establis complete,accurate, and representative information about current $ater consumption patterns& Arealistic assessment of urban $ater consumption is essential in understanding o$ te$ater suppl* department of te Mumbai Municipal #orporation can accommodatevariations in time and t*pe of use&

ptimi(ation of e)isting resources:

#onsumption patterns include a number of $ater use caracteristics representative of teindividual users& -ese caracteristics include, te number of inabitants to be supplied$it $ater and teir demograpics te consumption abits of te population te t*pe ofdevelopment, propert* si(e and propert* landscape& Cac of tese parameters pla* a rolein determining overall demand& -e Municipal #orporation of Greater Mumbai /M#GM0 asso far relied upon anal*sis of large'scale consumption patterns5 to evaluate managementoptions& But its municipal $ater managers toda* need to understand better te generalpatterns associated $it $ater use in te cit*& nce identified, te M#GM can curtail

demand b* evaluating alternative demand'oriented management options tailoredspecificall* to te different municipal $ards of te cit* to optimi(e and conserve e)istingresources&

Rain $ater arvesting troug p*sical storage

Altoug Mumbai is currentl* developing a compreensive $ater suppl* plan for te

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comming decade5, te #it* is no$ e)ploring conservation strategies at reducing demandfor municipal $ater suppl* in te future& ne of te strategies recentl* incorporated in te"evelopment #ontrol Regulationsin te unbuilt portion of te plots, ensuring percolation of suc $ater b* ensuring

tat, to te e)tent possible, te ground surface is porous and if surfaced, $it sami'porous materials and use te area of te side $alks of all roads to act as EcatcmentE b*surfacing $it perforated material so tat percolation of rain $ater is not arrested&-ere isa penomenal increase in te impervious land surfacing in te cit* /roads, footpats andlands around buildings0 tat is progressivel* reducing percolation of rain $ater into teground. -ere is an increasing tendenc* to pave te statutor* 1


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Footpaths paved with concrete tiles

Courtyards in buildings are paved for parking

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Open spaces like the one at Oshivara should be used to recharge groundWater

Goals:

-e goal of te rain$ater arvesting pro@ect in Mumbai sould be :

to create an understanding of geo*drologic s*stems b* producing 6'dimensional mapsof tese s*stems based on geologic information, interpretation, and interpolation

develop metods of caracteri(ing te 6'" geometr* and properties of basin'fill a%uifers&-e metodolog* and anal*sis $ill re%uire creation of a $ater related database, rainfallanal*sis of last atleast 64 *ears, anal*sis of montl* data for atleast one rainfall station ineac of te 26 municipal $ards of te cit* /using ?ertical Mapper 2&< of te MapJInfo GISsoft$are0 and ground$ater level anal*sis of 64 *ears of montl* data from atleast1control$ell in eac of te 26 municipal $ards&

Metodolog*

A%uifer boundaries sould be mapped using te litologies /e&g& till, silt, sand, gravel,etc&0 present& Kields can be divided into categories, sa* 4'144 litres per minute /lpm0, 144'


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Mapping average ground level of eac $ard $it reference to eac oter, mean sea leveland disposal troug surface drainage $it reference to ig tide and lo$ tide levels

Geological mapping of subsoil data and geomorpolog*, rock strata, under ground $atercurrents and porosit* of rock to determine of eac $ard to determine teir vulnerabilit* to+saliniation b* percolation of sea $ater during igJlo$ tides

Geo*drograpic mapping of a%uifers and streams in eac $ard, spread and capacit* ofa%uifers and teir ranking according to a%uifer capacit* and vunerabilit* to saliniationand draining troug live streams&

Mapping te levels of a%uifers and porosit* measurements to %uantif* rate of percolationfrom sea to a%uifer&

Mapping for matcing te capacit* of te a%uifers $it percolation rates %uantit* ofrainfall in eac $ard related to te +soft ground area availabilit* for $ater percolation

Ranking of Wards on te basis of te matri) of all tese parameters to prioriti(e taking uppilot pro@ects&

Ranking Metod:

-e anal*sis could utili(e AR# ?ie$ 6&2 GIS soft$are and could be structured around fourma@or steps&

First, determine te seasonal variation in $ater consumption in te cit* $it summerconsumption greater tan oter seasons& -e M#GM could use te cit* land'use andseasonal $ater consumption data to identif* $ards $it ig consumption rates&

In te second step a bivariate categorical comparison can be made bet$een te built areaand nonbuilt area of eac $ard& -e built area refers to te foot print of a building in a plot,and te non'built area encompasses te remaining open space in te plot & -e built areaand nonbuilt area can be broken in se%uences of s%uare foot increments based on te

capacit* of te non' built area to capture rain $ater and, tereb* recarge te ground$ater to te e)tent of feeding te built area&& An e%ual rainfall can be assumed across teentire $ard area and complete rainfall capture on built area and non' built area& A matri)can ten be developed based on te relationsip bet$een built and nonbuilt areas, andrank all plots across te $ard from igest to least conservation potential&

In te tird step, all $ards $it te igest percentage of comparable built versus non'built areascan be identified& $ards can ten be classified based on specified built versusnon'built increments to allo$ te Water suppl* department to assess igest conservationpotential& In oter $ords, $en selecting $ic $ard to target $itin te cit* forinstallation of rain$ater arvesting s*stems, $ards $it te igest number ofcomparable plot ratios can be cosen& -e #it* can target tese $ards for te pilotpro@ect&

In te fourt and final step, onl* tose $ards $it te igest conservation potential canbe used $it building area and istoric rainfall data to calculate potential for $ater capturefor te priorit* $ards& B* averaging rainfall data over te last 64 *ears during monsoonmonts te total runoff volumes from all residential buildings can be calculated in teselected priorit* $ards& -e rain$ater capture from tose $ards aving igest

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conservation potential $ill enable te M#GM to estimate te amount of $ater tat can beremoved from te storm $ater drainage s*stem in Mumbai&

In determining te amount of $ater re%uired for recarging of te underground ac%uifersin te non'built areas in eac $ard, te istoric meteorological data can be relied upon&Given tese figures M#GM can estimate te appro)imate amount of non'built areare%uired to irrigate specific areas of land $itin eac priorit* $ard& -ose plots $it teigest percentage of comparable areas $ill ave te greatest rain$ater arvestingpotential, $ile tose $it fe$er comparable areas can be assigned to EmediumE, andtose $it te least into a Elo$E categor*& As a result, all plots $itin te priorit* $ards $illfall into a ig, medium or lo$ categor*& -e indication of ig, medium and lo$ refers tobot te conservation potential and a strateg* to minimi(e te costs associated $it teinstallation of rain$ater arvesting s*stem&

Storm $ater drainage is an important consideration in Mumbai& Inade%uate capacit*6andoverflo$ing of tese drains resulted in te disasterous floods in Mumbai on August 2> in244


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C)traction of *drolog* /surface and ground$ater0 la*er along $it volumetricestimates,

Spatial distribution of surface $ater bodies and teir status,

8ist of surface $ater bodies /reservoir, tanks, lakes, ponds0 $it surface spreadand volume statistics,

Sectoral utilisation and potential for a0 Irrigation

b0 "rinking

c0 Industries

Cstimation of demand based data ' sector$ise,

Cstimation of sub'resource'$ise availabilit* based on modeling tools of run'off andrecarge components&

It is oped tat tis paper $ill elp te M#GM establis a basis and take up Pilot pro@ectsto e)amine fiscal and ecological implications of $ater conservation strategies using GIStecni%ues&

Foot Notes:

1 2001 Census population 0.97m. variously estimated at 14.20 to 15 m.. In 2006.

2 Mumai !as ori"inally made up o# 7 islands !$i%$ !ere later %onne%ted to t$e nort$ern suurs y a rid"e a%ross t$e Ma$im %ree& 'see map on pa"e (). *$e present area o# aout 4(+ s,. &m. o#-reater Mumai Muni%ipal Corporation is divided into 2( Muni%ipal !ards o# !$i%$ + #all in t$eisland %ity in t$e sout$ and t$e rest in t$e suurs nort$ o# Ma$im %ree&.

( /IM*3ri$an '-reater) Mumai tormater raina"e /eport o# MC-M estimated t$e!ater re,uirements and %apital out lay and pro8e%ts re,uir!ed to e ta&en up to au"ument t$esupply and ta&e %are o# t$e storm !ater and draina"e.

4 Mumai evelopment lan 19912010 y MC-M. *$e report a%%ompanyin" t$e p$ysi%al plan "ives

detailed in#ormation on demo"rap$yso%ioe%onomi% and p$ysi%al #a%ilities utilities.

5 evelopment Control /e"ulations #or Mumai:1991. *$ese are part o# t$e state "overnmentapproved development plan in #or%e #rom 1991 and pres%rie open spa%es to e le#t !it$in a

residential%ommer%ial plot o# land as a re%reation spa%e. ue to la%& o# stri%t en#or%ement andpuli% a!areness aout environmental e##e%ts o# %ontravenein" t$e re"ulations t$ese are oservedmore in de#ault; *$e ne! rules re,uirin" !ater $arvestin" emp$asiuly 2005 and possileremedial measures is made puli% in Mar%$ 2006. Mumai Floods:?n"ineerin"olutions:[email protected] is also o# revelen%e.

+ Miti"atin" Aran FloodsMumai India:imple olutions:ra&as$ M 3pte. *$e paper sumitted tot$e tate "overnment in t$e !a&e o# t$e delu"e on >uly 26 2005 !$i%$ resulted in loss o# over 900lives emp$asi


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en%oura"in" use o# per#orated pavin" tiles re,uirement o# $avin" oredopen !ells !it$in t$e ploto# lands #or residential uildin"s providin" seepa"e devi%es in all open storm !ater drains to#a%ilitate speedy per%olation o# !ater.

Bibliogap*:

1 Mitigating !rban Floods: Simple Solutions: Prakas M Apte& August 244

rainwater harvesting in mumbai

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