Introduction

Mumbai, is one of its 10 mega cities of the world and business capital of India. proper occupies a low-lying area that once consisted of seven islands called , Mazagaon, Old Woman's Island, Wadala, , Parel, and -Sion separated from each other only during high tide. The population has risen from merely 3 millions in 1951 to 12 millions as on 2002 out of which 50 % live in slums It also supports “daily commuting” population of 20 lakhs It covers an area of 437 sq.km. With average density of 36600 soul/ sq.km.

Water Supply-From Past To Present

Prior to 1870, the Mumbaikar used to drink water from the existing well, and tanks. But during middle of nineteenth century, because of the epidemic, decision was taken to build a dam to supply good quality of potable water, and then onwards Bombay water works started functioning The ’s water supply dates back to the 22nd June 1845. On this day, the then Government in response to the agitation of the native appointed 2 men Commission to report about the quality and quantity of water available in Mumbai. The Commission reported back within 24 hours that the water supply of Mumbai needed immediate attention. This was the beginning of efforts to search sources of water to satisfy the City’s demand. It is the first city in India to receive piped water supply in the year 1860.

Today it supplies 2950 MLD every day, is one of the largest water supply in Asia. Sources of Supplies are four lakes namely Tansa, Vaitarna, Vehar and Tulsi. about 110 km from Mumbai.The water is treated in two plants namely Panjarapur & and stored at two Master Balancing Reservoirs namely Yewai & Bhandup with 1910 MLD ,the largest water treatment plant in Asia and further supplied to the city through 26 service reservoirs. The entire network is spread over an area of 430 sq km, while the sources are 40 to 60 kms away from the Master Center.

WATER SUPPLY TO GREATER MUMBAI SNO Source of water supply Daily supply in mld Year since it commissioned 1 Vihar 67 1860 2 18 1879 3 lake 4 1891 4 Tansa river scheme 494 1948 5 Vaitarna- cum-Tansa scheme 490 1957 6 scheme 90 1967 7 Upper Ulhas scheme 550 1972-73 Source : CGWB manual on groundwater in urban environment of India

How Much Is Supplied? The Brihanmumbai Municipal Corporation is responsible for providing water supply, managing and operating the network and billing and collecting revenues to the population of Greater Mumbai ( more than 12 million people). The department in charge of these functions is the Hydraulic Engineer’s department. There are around 300,000 water connections in Mumbai.

Most of the supply is for domestic purposes ( 85 %). The non-domestic demand ( 15 %) has been decreasing over the years in parallel with the decline of water consuming industries ( mostly textile and dairies).The Municipal Corporation of Greater Mumbai presently supplies water at 135 LPCD to the consumers in planned development, which is recently curtailed to 90 LPCD because of rapid rate of development, constant influx in the city and no augmentation in water supply in near future. City today needs nearly 4000MLD of water. With an Status of water supply in Mumbai expected population growth of 2% per year, the 3800 projected water demand in 2011 will be 4500MLD. 4000 Water is supplied at the rate of 2980 MLD from 2950 3000 surface water. Average supply is around 240 to 250 2000 lpcd. However large discrepancies exist according to the type of settlement and the type of connections. 1000 Surface water provided to the city by a gravity system 0 is the main characteristic of the supply of Mumbai Million litres per day DEMAND SUPPLY where groundwater plays no role. Water is supplied on source: Braham Mumbai Corporation a rotational basis among the 107 distribution zones because of the reservoirs capacity. Intermittent supply is the rule in Mumbai and supply can vary from two to six hours.

Who Needs How Much?

WATER REQUIREMENT OF GREATER MUMBAI(1991,2001,2011)

5000 4525 3819 3529 4000 3080 2823 2521 3000 2200 2017 2000 1489 400 400 400 1000 38 54 69 90 90 90 0 Domestic Industrial Other uses Enroute Total (net) Total ( gross) Water Requirement(in MLD) institutional Type of Use

Note : The projected demand of water for Greater Mumbai for the year 2021 is estimated to be 5355 mld.

Source : CGWB manual on groundwater in urban environment of India

SITUATION ANALYSIS

Out of the gross water supply of 3,193 MLD, after accounting for leakages, the net availability amounts to 2,320 MLD. This includes 600 MLD water supply for non-domestic purposes, namely, industry and commerce. The water losses through leakages in water supply distribution system amount to almost 25%. This is very high despite the MCGM efforts to reduce the same to 15%.

SOURCES OF WATER SUPPLY 700 590 550 600 494 500 400 300 200 67 90 100 18 4 Capacity(MLD) 0 Vihar Tulsi Powai Tansa Vait Ulhas Upper lake lake lake river arna- river Ulhas scheme cum- scheme scheme Tansa

*Expected year of completion-Gargai-2009 & Shai-2009.

* The average gross per capita water supply is 260 litres, while the net water available for domestic use is about 155 litres per capita per day (lpcd). This net availability no doubt exceeds norm of 135 lpcd set by the Bureau of Indian Standards (IS). Apparently, the water supply status appears to be satisfactory on the whole. However, the fact that there are a good number of private water suppliers and a conspicuously large market for water provides elegant testimony of inadequacies of water management in the city. * Surely, the aggregates should not give any complacency to the municipal authorities. The spatial, temporal and sectoral coverage of water is still missing i.e., some parts of the city do not receive water; some of them receive it intermittently; and some sectors have more privilege in accessing it than others.

Connection Nature of Use Tariff (Rs per thousand litres) Metered: Domestic -Slums/Chawls 2.25 -High rise buildings 3.50 Commercial/Industrial 10.50 - 38 Unmetered: Domestic 65% of the rateable value Commercial/Industrial 130% of the value rateable value Source: Municipal Corporation of Greater Mumbai (2002)

Moreover, the municipal norms of water supply have been fixed at 45 lpcd in slums, 90 lpcd in chawls and 135 lpcd in high rise buildings, respectively. However, the actual water supply widely varies between wards and even localities within a ward. For example, it varies from 50 lpcd in slums to 250 lpcd in high rise buildings.

What Will Be The Future Supply?

FUTURE SOURCES OF WATER SUPPLY The present supply versus demand percentage satisfaction is about 76 %. Looking to the growth of city and day- by- BHATSA ( 350 MUMBAI III A) day increasing demand, there is an urgent need to identify MIDDLE and commission new sources of water supply. Govt of 865 VAITARNA has allotted additional 350 MLD of water 455 GARGAI from Bhatsa sources. This project is known sa Mumabai III-A project. 455 PINJAL

This project has been taken up on priority basis to utilise this additional water from Bhatsa source. The estimated cost of this project is Rs 700 crore. This project is expected to be completed by the end of year 2007.The important components includes several works like raising height of Pise weir by 2m (work completed ) ,laying of 3000 mm dia main from Pise to Panjrapur (total length about 9 kms Part of the work of 3 kms is completed.),pumping station at PiseTreatment plant of 455 MLD capacity at Panjrapur, raw water pumping station of 635 MLD capacity at Panjrapur ,tunnel from Bhandup comlex to Malad Hill reservoir and further extension upto Liberty Garden and Charkop, tunnel from Veravli Hill reservoir to and Yari road.and laying of 3000 mm dia water main from Mulund Goregaon link road to Amar Mahal along

The future sources of water supply to Mumbai city to fulfil the requirment have been identified.

The identified sources and the estimated yield from each source is Vaitarna river basin and Ulhas river basin are as under:

Vaitarna River Basin 865 Water from sources in Vaitarna river basin can be 1000 brought to city by gravity. The feasibility report 455 455 500 for Middle Vaitarna project has been completed. The final technical details like type of dam, etc.is 0 being worked out. Most of the clearances required Capacity(MLD) Middle Gargai Pinjal have been obtained. However, clearance from Vaitarna Envrionmental Department of Govt. of India is yet awaited.

The major components of works identified in Middle Vaitarna project includes a location of dam between Upper Vaitarna & Lower Vaitarna, tunnel of 3500 mm dia length of 8 kms from ( vaitarna) to Y-branch ,a 3000 mm dia water main between Y- branch and Gundavali for a length of about 33 km in different stretches and additional treatment plant at Bhandup complex of 590 MLD capacity.

For Gargai and Pinjal sources the water can be transmitted to Modak Sagar through tunnels by gravity. Further from Modak Sagar water can be easily brought to Bhandup complex with existing and additional conveyance system.

It would be beneficial to tap sources from Vaitarna basing from where water can be brought by gravity upto Bhandup complex where, adequate land for accommodating additional treatment plant and to enhance the capacity of Master Balancing Reservoir – I is available at appropriate elevation. The treated water can be pumped into Master Balancing Reservoir at a fairly low head ( 18 m) . This would save operative cost and conserve electric power.

Ulhas River Basin 1500 The water from Ulhas river basin has to be abstracted and 1090 conveyed by pumping. Two stage pumping is necessary i.e., 1000 590 from pick up weir at Pise to treatment plant at Panjarapur, and 500 from treatment plant to Master Balancing Reservoir – II at Yewai Hill. Looking to the problems that have arised in Capacity(MLD) 0 pumping system in the last two decades, it will be beneficial Kalu Shai to minimize pump supply and to adopt gravity supply to the extent possible.

Advantages of gravity system of water supply from Vaitarna river basin compared to pumping system of Ulhas river basin includes less prone to pollution at source than that abstracted from Ulhas river basin. Secondly, cost effective as saving of about Rs 50 crore per annum in operative cost. Thirdly, comparatively assured water supply due to non- dependency on power supply. Fourthly, land required for locating treatment plant facilities and for laying transmission system is already available with Municipal Corporation of Greater Mumbai ( MCGM).Fifthly, population affected by developing sources of vaitarna basin is comparatively much less.Sixthly,the numbers of villages need resettlement are 8 as against in Ulhas basin. moreover the area under submergence is less, in vaitarna basin 3473 hectatres as against 5108 hectares in Ulhas basin .Lastly it requires recurring expenses on maintenance of electrically operated system due to limited electrically operated system.

Water Pricing – Who is Paying how much?

Consumers have to pay water and sewerage charges when the connection is metered, and water and sewerage tax when the connection is not metered, water and sewerage benefit tax for all consumers. Since 1995-1996, the total revenue income has doubled while the expenditure has increased by 1.5 times. All the proposals to separate the water supply and sewerage department and to create a water board have been rejected by the corporation. In order to improve the cost to recovery (today;80 %), the centralised computerised billing is being decentralised at the ward level. Till as late as May 1997 the water charges were as low as 60 paise/ 1000 litres and after that tariffs are revised three times and present rates are adopted with effect from 01.08.2002.

Water charges are as follows ( Rs. Per cu m):

For domestic consumers: Rs 1.75 for slums and Rs 3 for others For hospital, hall et al: Rs 8 For industrial establishments: Rs 15 For commercial establishments and other industries : Rs 22 For 3 star hotels : Rs 35

In addition, consumers are also required to pay water benefit tax at 12.5 %. Also, as 70 to 80 % of water supplied exits as sewage, sewerage charges are collected at a rate of 60 and 39 % of water charges in case of metered and non-metered connections, respectively. For commercial/industrial units, this is 78 per cent. This hike ( from 1.75 to 2.25 Rs. Per cubic meter for slum dwellers and from Rs 3 to 4 for other domestic users) will, according to estimates , bring an additional Rs 51 crores to the BMC’s revenue ( the Times of India, 2002) The tariff classification under water charges rules is as under:

Category of consumer Tariff in Rupees per 1000 litres* Domestic Stand post 2.25 Buildings & chawls 3.50 Halls, Hospitals, Playgrounds, Swimming pools etc. 10.50 Industries, Dhobi ghats, Central & State government premises etc 18.00 Shops, Restaurants- I, Cinema Halls, Refineries, Airports, Public sector 25.00 undertakings etc., Race course & Star hotels 38.00 • Note : Sewerage charges are at 60 % of water charges.

Since 1987, domestic rates have been multiplied by five and 10 respectively for slums and others. Other tariff categories have also been increased but to a lower extent ( less than three times for commercial establishments for instance). Sewerage charges are equal to 60 % of the water charges since April 2000 and have to be paid whether or not they have a connection, a situation similar to the one in Chennai. Water and sewerage charges are collected every four months if the bill amounts is below Rs 3,000 and every month otherwise. The bill collection is carried out by the Hydraulic department

Comparision of water charges billed for different cities in India with different levels of consumption

STATE\AGENCY Water Tariff(Rs/KL) Water Water Tariff(Rs/KL) Tariff(Rs/KL) DOMESTIC COMMERCIAL INDUSTRIAL Hyderabad Municipal Water Supply & 3-10 6-12 6-12 Sewerage Ahmedabad Municipal 1.50 4.00 4.00 Corporation Nagpur Municipal 2-2.50 4.00 10.00 Corporation Madras Water Supply 30(Flat) 10.00 25.00 &Sewerage Delhi Jal Board Upto 10KL/ month Upto 50 KLs/month @ Rs 5/KL+50% @35paise/KL +50% Above 50 KLs @ Above 10KL and upto 20 Rs10/KL+50% Minimum Charges @ KL/month @ Rs rs 100+50% per 1/KL+50% Above 20KL month/connection and upto 30KL/month @1.50/KL+50% Above 30 KL/month @ Rs 3+50%

Calcutta Municipal 5.00 100-200/month Development Authority Bangalore Water Rs 65 upto 25 KL @ Rs Rs 275 upto 10 KL Rs 60/KL Supply &Sewerage 2.60/KL for more than for more than 100 KL Board 100 KL,Rs 33/ KL. Rs 60/KL. Tamil Nadu Water 2.00 4.00 6.00 Supply & Sewerage Source:P.S.Rana,Integrated Urban Infrastructure In vestment and HUDCO’s Lending Programme,Paper Presented in the International IHSP seminar on ‘Integrated Urban Infrastructure Development held on 1-4 February,1995 ,New Delhi, in Urban Statistics, Handbook 2000,NIUA,New Delhi,pp-103-104 S.K.Rohilla et.al,Delhi’s Water AND solid Waste Management-Emerging Scenario.

To sum up, cross- subsidies are the rule as in many other Indian cities as industrial and commercial establishments have to pay much higher rates than domestic connections. However, unlike most of other cities, slum dwellers (in recognised settlements) are considered as customers and have to pay water and sewerage charges and taxes. In any case, the tariff policy is not based on economic principles and no change of tariff structure is thought of. Water supply and sewerage is a good source of revenue in Mumbai but the lack of independence from the corporation, for instance through a board, is a constraint towards efficient management.

Water Leakages-What is the scenario?

The leakage study world over indicated that the wastage of water, more popularly know an Unaccounted for water ( UFW), ranges from 8 % to 12 % for developed countries and same for the developing and non- developed countries is in the range of 20 % to 70 %. In Mumbai the estimated UFW is in the range of 20 % to 25 %. The 15 % leakage is considered as acceptable in a distribution system because further reduction efforts are not cost effective. In Mumbai the waste prevention programme was systematically implemented, by introducing a Leak Detection ( LD) Cell, since 1973. The entire city is divided in 615 leak detection zones. Water mains in each zone were thoroughly checked for leakage by sounding instruments periodically. The initial leakage and losses after attending repairs to defective mains were compared to arrive at quantity of water saved. The process was laborious and in fact with diligent efforts the total leakage was brought to about 15 % by mid- eighties. This was very close to acceptable limits of allowable leakage in a distribution network.

Pipe Lines-are they sensitive to weather condition?

The water supply system of Mumbai is of intermittent type and thus water mains are subjected to alternate wet and dry conditions, a very conductive condition for corrosion and rusting. The materials of water mains constituting conveyance, distribution and communication network are Mild Steel, Cast Iron, Ductile iron and Galvanised iron. Recently High Density Poly-Ethylene ( HDPE) , Medium Density Poly Ethylene (MDPE) and Glass Reinforced Pipes ( GRP) material also used for laying pipelines in particularly hostile conditions and creek lands.

Thus in Mumbai, even in the most hostile surroundings, the water mains of different materials are adequately protected against corrosion by adopting various anti- corrosive measures by MCGM.

Where Waste Goes?

Mumbai generates 5,500 metric tons of organic and inorganic waste daily. Only about 5,000 tons are collected daily by the BMC, which spends approximately Rs. 135 crores a year for garbage collection and disposal. There are 6.300 garbage collection points in the city and its suburbs. Citizens do not pay a special tax for garbage clearance. BMC employees and contractors lift the garbage and deposit it in the four dumping grounds at Deonar, Malad, Gorai and Mulund. The Deonar grounds take about 70% of the total. The capacity of these landfills will expire around the year 2010. BMC employs about 20,000 workers for solid waste management. Each worker is paid Rs. 3,200 per month, around Rs. 3,000 travel allowance, and up to Rs. 1.25 lakhs in housing loans with minimal interest. In 1988 a report on the health of BMC workers pointed out that 67% of the workers complained of choking, breathlessness and sever burning sensations in the eyes each time they went down a manhole; that spines collapsed from the cramped working conditions; that skin disease and gastrointestinal tract infections were so commonplace as to be beyond comment.

Collection, Transportation & Disposal of Town Solid Wastes

Quantity of Average Solid Waste collected daily is 4,000-4500 tonnes of refuse(Approx) and 2,000-2500 tonnes of debris and Silt (Approx.) The total staff for Conservancy and transport is 35,601, 4244 respectively. The total expenditure of 1999-2000on conservancy is Rs 323.6 Crores (Approx) and on transport is Rs.79.37 Crores (Approx.).Total No. of vehicles used for refuse collection. is 953 for refuse plus debris(Contractor) and 509 (Refuse) + 731 other service Municipal vehicles .Land filling methods, processing/treatment to convert into manure,pelletisation and vermi composting are different modes of disposal. The main dumping grounds are at Deonar ,Mulund, Chincholi and Gorai (Borivli).

According to survey, the pollution levels are very high in Khar and Maravali and pollution of the is a cause for concern. The city produces 2671 MLD of sewage and 6256 MTD of solid waste. Sewerage Sewerage for the city is managed by the Water Supply and Sewerage Division of the BMC. Only about 80% of the city's area has sewerage. There is a pumping station with a marine outfall at Love Grove in . A similiar pumping station at is planned, as are aeration lagoons for treatment of sewage at Malad, Versova, Ghatkopar and Bhandup. Information on a World Bank loan for a water supply and sewage disposal project can be accessed. This program has also received Japanese aid. The Ghatkopar and Bhandup stations, with their Waste Water Treatment Facilities are expected to start functioning by 1998. The plan for a lagoon at Malad has been cancelled because the Malad creek is unable to carry sewerage. The National Environmental Engineering Institute (NEERI) will check the quality of coastal water at the outflow from the Versova lagoon. An Indian firm, AIC Watson, is performing the topographical survey for an assessment of the water level and conditions of manholes in the city. A German form, GKW, is preparing a detailed report on the structural condition of the city's sewerage pipeline. A Canadian firm, R. V. Anderson and Co, is conducting a survey of the operation and maintenance of the entire sewerage disposal system, including the human component such as information systems, staff etc.

Sea water or Sewage Water?

Water pollution in Maharashtra goes unchecked.90% of sewage water generated by municipal councils and over 50% of sewage discharged by municipal corporations goes untreated, CAG said in its latest report. This untreated and treated waste mixed with industrial effluents, was discharged through seven outlets. Of this 1594 MLD was directly discharged in to and 973MLD was discharged into creeks than eventually merged with the sea, makes it highly polluted and unfit for bathing, water sports and commercial fishing.

Is Water Quality Is A Issue?

Despite the result of the study conducted by Dr M M Bapat and Dr T N Mahadevan (1999-2002 ) which talks about the physical, chemical and bacteriological aspects that they should satisfy and the desired quality of water must be maintained up to the point of ingestion of the consumer. Though the result of the reservoir water analysis clearly indicate that the quality of water being supplied to the city of the Mumbai, at the point of supply, is unquestionable and at par with international standards ,the levels of bacteriological polluted is more than 20 % in most of the wards, the maximum being 70 % in ward M/E. Hence, attempts were made to located the probable causes. The contamination of water supply were largely due to unsanitary conditions of surrounding,. negligence towards hygiene, no timely cleaning and maintenance of underground suction tanks and overhead distribution tanks situated in the residential areas. While, infiltration of sewage through water mains is because the drinking water mains and sewerage pipe lines running parallel to each other. In some localities the drinking water connections run through puddles of sewage water, defecation on the mains by slum dwellers and because of leakages in service connections

Almost all the co-operative housing societies in Mumbai invariably practice storage of water in underground tanks (UG) during the restricted supply hours and regulate supply to residents by pumping into overhead tanks (OH) twice a day depending on availability of water. Wastage of water due to overflows from both storage facilities were seldom seen since the supply is relatively limited. Most of the residents also store the water in their premises for various utilities including cooking since the demand supply position supply position is not matching well. Use of the commercial water purification kids with either UV or other sterilization methods were practiced at least in 20 % of the housing colonies covered. Even this depended on the socio- economical status of the residents. Since the BMC distribution network is dry for a major interval of time everyday causing partial vacuum in the system, the chances of sewage or other wastewater getting sucked into the pipeline through inadvertent perforations in the pipeline cannot be overlooked especially in areas where the municipal water lines run along sewage water pipes or are submerged in the wastewater. Overflow of raw sewage system could be seen invariably in many locations. A few recognised slum colonies who also enjoy all the municipal service facilities were considered. These include : Atomica Society, Narayan Guru Society, Assisi Nagar, Chempazhanthi society, Sri Narayana society, Sankara society, Buddha nagar, Gautam Nagar. Samples were collected at the time of supply, from storage tanks, at house levels with and without filtration, Aqua Guard water etc. A total of 160 samples for microbial and 80 for chemical parameters were analysed. 70 % of the samples analysed for MPN were found to be contaminated. Even Aqua Guard filter indicated sporadic contamination by MPN when in excess.. Nitrite concentrations were also high as compared to other areas. Sediments and some organisms were also noticed during the survey period. The analysis of bore well water sampled from areas in and around Mumbai led to the observation that nearly all the parameter values ( chemical as well as microbial) were quite high as compared to the values seen in case of the municipal water supply samples. Many of the samples crossed the permissible limit values of BIS in the case of Alkalinity, Total Dissolved Solids ,Total Hardness, Calcium, Hardness and Magnesium hardness Most of the samples were found to be unpotable with respect to the microbiological parameter ( MPN) as well, since the Faecal Coliform counts exhibited by these samples were generally _> 1600 FC / 100 ml.

Rain Water Harvesting- Reclaimed land and threat of salinity, quality of water—of both municipal supply and tankers., unequal distribution, wasteful consumption pattern—leading to over withdrawal from sources—heading for urban- rural conflict?, Therefore, overall water management is the order of the day—with RWH as a key component

What Government Is Doing?

Mumbai Municipal Corporation has made rainwater harvesting mandatory to the properties having plot area more than 1000 sq.mts. coming for development after 1st oct 2002. The condition is also being extended for the properties, which started development earlier, but are being completed now. These conditions will also be made applicable to existing buildings in near future. Recycling has been made compulsory for buildings having centralised (water cooled) A.C.plants. Henceforth M.C.G.M would grant residential water connections at 90 lpcd. No municipal water for flushing requirement. The properties are expected to generate the flushing water either by Rainwater harvesting or by recycling.

On 14th Feb.2002, Water supply & Sanitation Department of Government of Maharashtra has issued a G R. approving Rain Water Harvesting as a means of improving water supplies. The G R details various techniques of rain water harvesting, their costing & availability of funds. In furtherance Municipal corporation of Greater Mumbai has issued a Circular insisting provisions for rainwater harvesting while developing plots having area more than 1000 sq mts, as I.O.D. conditions from 1st Oct. 2002. The design of rainwater harvesting system shall be prepared by approved consultant in the field & shall be to satisfaction of the corporation. Further all centrally air conditioned building shall have their own waste water treatment plant & treated waste shall be used for cooling purposes.

Rainwater Harvesting Potential In Mumbai-Is It Viable?

To look at potential of rainwater harvesting it is essential to look at the climate, especially rainfall pattern . The climate is equable with very little seasonal fluctuation. January, the coolest month, has a mean temperature of 24 deg C May, the warmest month, 42 YEARS MEAN TOTAL PRECIPITATION averages 30 deg C Seasonal fluctuations of humidity and rainfall are more significant than those of temperature 700 650 600 566 487 500

400 355

300

IN MILLI METRES METRES MILLI IN 200 88 100 000012 5 0 0 July May June April April March August October January January February February December December September November November MEAN NUMBER OF PRECIPITATION DAYS

30 24.9 25 25

20 17 15 15

10 NO. OF DAYS 4.8 5 1.6 0.1 0.1 0.1 0.3 0.9 0.3 0 July May June April April March August October January January February February September December December November

The average annual rainfall is 2,170 mm (85 in). Because of the southwest monsoon winds, more than 95 percent of the annual rainfall occurs during the four-month period of June through September. Mumbai also has high humidity, with an annual average of 87 percent.

Area of Mumbai – 437 sq kms Annual avg .rainfall – 2000 mm Total rainwater falling over Mumbai = 437 x 1000000 x 2000 lit = 874000000000 = 2394.52 MLD

Present water supply = 2900 MLD

Even if we assume 70 % of the area to be developed, 50 % of it to be roofed and we collect 70 % of the water falling over it, the quantity of rainwater that can be harvested works out to 589.34 MLD. This is a sizeable quantity compared to water supply to Mumbai.

Are You Interested-What Needs To Be Done ?

One has to get the approval of designs from the rainwater harvesting cell. headed by Ms Suprabha Marathe, Assistant Engineer. The office is located at 5 th floor, Municipal head office, Mumbai. The cell is also having braches at its 24 wards that cater the need of the public. Ms Marathe says it is necessary to centralize because rainwater harvesting should not lead to contamination of underground aquifers.A person who wants to rainwater harvesting has to send to BMC the society plan showing building, water requirement of the society, roof size, area of open premises and also details of suction tanks , septic tanks, flushing network and inspection chamber position. And if they have any borewell then its details has to be given Once a client submits his plan they the RWH cell superimpose the design on the drainage map and ensures the water harvesting structures do not affect the existing water line and sewage lines. More over the cell also goes to the site to ensure that quality of the work is maintained.

Challenges !

Ms Marathe says that rainwater harvesting will be challenge in Mumbai, considering the existing condition in Mumbai, like easy available of municipal supply and at cheaper rate. More over the geology is also complicated in Mumbai. She says that previously the Mumbai was a group of seven islands; the gaps between the islands were filled up in due course. So in one place a person may get water at 3 ft and other place one might touch water at around 70 or more depth. So according to her considering the situation the success of rainwater harvesting in Mumbai can be taken a big success story unlike the other Indian cities.

She further told that she has deliberately taken up sites where the seawater intrusion has taken place and the cell will be monitoring the water quality in these wells. To find out the improvement of water quality by rainwater harvesting, She further told that rainwater harvesting is at the early stages and it will take the end of the year to actually say the impact of water harvesting in Mumbai.

She said that the to create awareness among the public cell in the last six months have conducted workshops for Architect, Plumber and Engineers. According to her in mumbai both recharge and storage methods are practiced. The old abandoned storage tanks were repaired and used for storage purpose and the excess.

CASE STUDIES

1. DEPO, THE BOMBAY ELECTRIC SUPPLY AND TRANSPORT (BEST), MUMBAI.

Case Background

The rooftop area of the shed is about 350 sq.m. The main source of water for the Back Bay Depo was from municipal supply. BEST is having 25 bus depose in Mumbai, among them currently around 14 bus depos are having rainwater harvesting storage tanks.

Measures taken for water harvesting

The annual water harvesting potential from a rooftop are of 360 square meters is 6.54 lakh litres. The water harvesting system was installed in 1987. Since the rainwater was stored in the existing sump, which used for storing the municipal supply the cost was negligible.

Rooftop rainwater harvesting The rooftop rainwater is diverted from the rooftop using 100 mm cast iron pipe to a Underground storage tank of 35,000 litres capacity. The tank is of 14.6m length, 1.20 metre width and 2.0 metre depth. The rainwater stored in the tank is pumped using motor and used for washing the buses.

The management initially used to wash the buses manually, where around 600 to 700 litres of water is used for cleaning one bus. And also the amount of water spend depends on the efficiency of the worker. So the engineering section using the available metal scrap devised a washing system. This system washes the buses automatically is 12 minutes and with 150 litres of water only. They also devised a quick wash system in which around 40 litres is only used for washing the bus.

Impact BEST gets municipal supply water at the rate of Rs 30 for 1000 litre of water. In the absence of BMC water they used to go for tankers, which is around Rs 460 for 10,000 litres. By adopting rainwater haveThey save annually Rs 50,000 by rainwater harvesting.

2. TATA INSITITUTE OF SOCIAL SCIENCES ( TISS), CHEMBUR, MUMBAI

Case Background

The area of the campus is about 42,500 sq m. Approximately 400 students and 250 staff resides in the campus. In addition to this there is a floating population of 350 people, who visit the campus for seminar and workshops. There are four bore wells and three municipal water connections for the campus.

Measures taken for water harvesting

a) Rooftop rainwater harvesting

The rooftop rainwater from the Hostel building is diverted to a storage tank of 1000 litres capacity. This tank is provided with a over flow arrangement also. The water from the tank is used for non potable purpose through a G I pipe which is connected from the bottom of the tank. Six drums of 100 litres are positioned at various spots, within the premises to collect the rainwater that falls on the terrace. The drum are placed near the dinning hall near the director bungalow and at various locations near the sprouts. The rainwater collected in the drums are used for mobbing floor and washing utensils.

b) Surface runoff water harvesting

The surface runoff near the director bungalow is diverted to a recharge pit of six feet depth near the existing borewell. This water collected in the recharge pit helps in recharging the borewell.

3.ASIAN PAINTS , BACK BAY DEPO, THE BOMBAY ELECTRIC SUPPLY AND TRANSPORT (BEST), MUMBAI.

Case Background

The total rooftop are of the campus is about 10,280 sq m. The main source of water for the factory is the municipal supply. The water harvesting scheme is prepared to collect 50,000 litres per day during monsoon season.

Measures taken for water harvesting

The rooftop rainwater was filtered and stored in the existing sump and after filtration it is used for factory purpose.

The first phase of rain water harvesting was to collect the rainwater from the Paint House terrace (average 23 KL/day) and collect in the old fire hydrant tank of 185 KL. The detail engineering design for connecting the drain coming down coming down from the terrace of Paint House to a single drain line and leading to the collection tank ( Old Fire Hydrant Tank) was made and a dual media filter was incorporated in the scheme for the filtration of collected water before use in the plant.

Impact At the end of the monsoon season of 2002, more than 23,00,000 litres of rain water was harvested, a season when not much rains happened and the scheme was implemented in the mid of July month. The quality of water collected was found to be similar to that of water supplied by BMC in terms of organics and inorganics.