Rain Water Harvesting in Bangalore - A Report

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Growth in the no. of buildings with RWH facilities over the last one year.  







No. of new installations






MoM growth in the no. of new instalations



























A Comparison of number of buildings with BWSSB connection, bore wells and RWH facilities:


No of Borewells

No of Connections

% of buikdings with borewells

No of building with RWH

% of buildings with RWH













South East
























Grand Total










  1. Approximately 920 additional buildings are implementing RWH every month over the last year. Over the last three months the rate has increased to 1300 buildings per month.
  2. As of Feb around 10000 buildings had implemented RWH.
  3. At a rate of 1300 houses per month, it would take 35 years for all buildings with BWSSB connection to implement RWH.
  4. Roughly around 1.8% of buildings with BWSSB connection have implemented RWH.
  5. 1 in 5 buildings has a bore well, 1 in 55 buildings has RWH facilities.
  6. The rate of RWH installation might increase over the coming months with the govt making it compulsory.



  1. Parks and open grounds are ideal for rain water harvesting.
  2. RWH at place like Cubbon Park and Lalbhag should be taken up as pilot projects.
  3. Corporators should take up RWH projects in local parks (we should move away from lawn/garden concept to mini forests).
  4. Thanks to ingenious brains for engineers at BBMP most storm water drains have now been concretized, leaving no scope for water to seep into the ground. Can these drains be re-modeled to have RWH pits at every few meters?
  5. It should be made mandatory for flyovers and underpasses to have RWH features.


Please see the attached documents provided by zenrainman for exact zone wise distribution. Thank you zenrainman for  sourcing and sharing the data. The data in excel sheet has not been fully verified (OCR of the pdf doc).



rainwater2.pdf313.97 KB
rainwater.xls43.5 KB


RWH issues.

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I am a little sceptical about this RWH stuff. I've been planning to get RWH done but when I talk to people there are various aspects of the whole thing which are bothersome. For one, it seems like most people are just simply buiding a hole in the ground and allowing the water to go in there - to recharge groundwater. Apparently, according to one of the companies I dealt with - Farmland Rainwater - it seems like this is not good as the soil in Bangalore is not permeable enough - too clayey and so the water simply stagnates and that could lead to other problems - mosquitos etc. A solution to this is to connect the RWH to a borewell but then not everyone has borewells.

The other possibility is to connect the RWH to the sump system directly using a filter. The problem with this is whether the water is clean enough. At least in my place the trees could cause a problem as leaves are constantly falling on the roof so the roof has to be cleaned very regularly. Added to this the occasional monkey doing its job etc. The RWH company guy says that the filtre is good enough to make the water potable but one always has ones fears.

Finally, I think one problem with RWH is that the city water is too cheap. Even with a 200% increase the cost is negligible compared to other things - like cable TV or internet or electricity. So there is little incentive for some one to install RWH as even with the best estimates it takes about 20 years to recover the cost.

At the end of the day, there seems to be Rain Water Harvesting of different flavours. I fear that what the BWSSB has mandated will have no real effect as most people will do the `nam ke vaste' thing and this, while satisfying the mandate, will not really help.




Rain Water Harvesting

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 I am not sure this thread is the place where we want to sound of about RWH. The goal of this thread is to more discuss the Water Index Project.  Nevertheless, some quick comments.  

According to examples that I have seen and after a conservation with an official of the Central Ground Water Board (who had come for a road show in our office for earth day), properly done ground water recharge works.  It may not necessarily recharge your own borewell or open well, but it definitely helps the community GW levels and by extension, if everybody does it, your own ground water level. it works in many parts of Bangalore, although it may not work in certain locations depending on the geology.

About directly filtering and using rain water, I have my skepticism.  Few reliable people have affirmed that they have tested harvested water and that it meets all potable specs provided the terrace (harvesting surface) is kept clean.  Until I get a chance to verify this myself, preference is to trust the data.

Finally, do not do a return on investment computation.  There is money you pay from your pocket and money society pays and by extension we do, through increased pain or taxes. What is the cost of increased ground water depletion for each of us.  Hard to put a monetary value.

This much is accepted the world over.  Increased built up area limits ground water recharge that was naturally occuring.  RWH is one way to use this precious water and to lower other impacts such as flooding.


Hi I want to make it clear

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I want to make it clear that at no point am I against RWH. What I am sceptical is about is what BWSSB wants to pass off or have done by most people as RWH. 

About the cost involved - its easy to say that in the long run etc. its worth it - and such and argument will work with me and most people who read Praja. Unfortunately, that is a negligible percentage of the population of Bangalore and most people don't think too much about the long run.

While I think the initiative by BWSSB is a good thing I'm pretty sure that in 90% of the cases it will not be effective. What I think is more important is perhaps instally RWH in public places such as parks. And also making sure there is no wastage of water through leaky taps / toilets etc. Pretty much any public tap -  in restaurants etc - leaks. As it is hard to penalize such violations the only way is to make the cost of water high enough to that people take care.

Think about it - if a tap drips 40 litres a day for 30 days - that 1200 litres. This costs Rs 12. A new tap costs at least Rs. 400. Why would a restaurant owner fix it as the cost of replacing it would only make it worthwhile in three years ? 





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that is a negligible percentage of the population of Bangalore and most people don't think too much about the long run

Actually that 'most people' have no choice, thats why it has been made compulsory. Believe me those people will bribe the administrators to get away or delay to the maximum, even if it means in the long run they will pay more on bribe than they would have implementing RWH. Common good isnt on those peoples mind anyway even if you educate them.

Effective touch points

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When told of the lack of awareness, the BWSSB official said: “We have been conducting street plays explaining the significance of rainwater harvesting and also have mobile information units in action. - Source

They have failed to use the most effective direct customer touch points. The meter reader & the bill payment interface.

'Have you implemented RWH already?'

YES - 'Thank you very much. You wont be asked this question again after an inspection can confirm the successful installation of RWH at your facility. If we fail to inspect in time before the next bill we will extend your grace period appropriately'

NO - 'This is the n+1 th reminder, You have i months before you will be fined j amount. You have already answered No to this question n times. The next awarenness session is @xyz location on mm/dd/yy hh:mm. It will provide information & contacts. In case you want to engage a trained plumber pl call 080-12345678'

Above is simple school grade computer pogramming and should be standard information printed on the bill at every bill payment interface be it a personal interaction by the meter reader, bill collectoror a kiosk touch point.

Rain Water Question

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Okay, I have a question concerning the potability of Rain Water. I cannot seem to find a reasonable answer from looking on the web or searching through Praja.

Tomorrow I am going to get RWH done and what we are planning is that the water will be fed to the sump. So this means that it will be used directly by us - not for drinking water and not usually for cooking but for other things - such as brushing teeth and showering. We will be using somthing called a Rainy Filtre which filtres up to 250 microns. However there is no biological purification - so perhaps bacteria or viruses coming in from the gunk on the roof - and other particulate matter can enter the system

So my question is whether someone else has done precisely this ? That is, connected RWH directly to the sump and is actually consuming it. Most people I know have either connected the RWH system to a groundwater recharging hole in the ground or to a borewell. I am not so keen on the hole in the ground as I was told that the ground in Bangalore is not so permeable so the water remains for a long time and could lead to other problems such as mosquitos or  overflow. We dont have a borewell so the other option is not possible.

The company says the water is potable but they cannot guarantee biological purity. So I was hoping to get some feedback on this issue. My plan now is to get the water tested before and then after to see whether there is a significant change.






RWH - plainly the way out

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Including Cauvery 4th stage, BWWSB will be pumping close to 1000 MLD (million litres per day) into Bangalore. With an annual average rainfall of 970 mm, if we can harvest the entire rain falling over the 800 sqKm forming the extended BBMP, it will give us 776,000 ML in a year, or 2130 MLD.

If we can harvest a 50%, we would be getting more than the equivalent of the present pumping, and all for free.

Very clearly, increased RWH is the answer.


Muralidhar Rao

fairly safe

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As long as the water does not collect any harmful chemicals while flowing into your sump, it can be considered safe enough for all purposes other than drinking (including brushing your teeth). During the course of the flow, enough of aeration is happening to neutralise a large part of the contamination like those caused by the monkeys' droppings, etc, which besides gets diluted over the comparatively larger volume of water.

So, make merry! Happy rain water harvesting!

Muralidhar Rao


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I think zenrainman is the person who should respond to your question about the potability of harvested rainwater (last time i checked he was travelling). From the limited knowledge i have, one of the ways to preserve the water would be to add chlorine. Chlorine will take care of most of the biological issues.

Rainwater Harvesting and BWSSB illegal approach vote based?

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Extorting by criminally intimidating some 60,000 residents of 40x60 and above property owners old residents of Bangalore into installing rainwater harvesting apprears arbitrary and capricious.
What is the contribution these unfortunate's can make for the bludgeoning city and its water problems?
Particularly so
1)when 60 percent of the city's space is occupied by public spaces owned by the government,
2) After receiving crores of  soft loans and UN funds for these projects, the RWH projects should be encouraged by subsidies as were solar water heating systems.
3) intimidating and threatening the customers with unauthorized abrogated powers of disconnection and stopping of sewerage. We still cannot fathom the stink if BWSSB can ever conceive of a mode of enforcing this illegal criminal intimidation.
4) by excluding the smaller site owners but votebank wise significant BJP as a novice government appears to be driving  towards permanent antagonization of the  citizenry by their mostly unpopular so far actions.
5)   When they are planning on crores of  tender or build-operate-and-transfer systems, they should  easily include the pittance cost of these 60,000  RWH installations and the drop of water they recharge the table,   of the present consumption  Three billion litres per year
6) The government administrative machinery fully aware of this alienation appears to be proactively driving this novice government towards an irrevocable total  alienation of even  the pro party electorate in a  mythical Ashatthamo Hatah Kunjarah  style. 
Under these circumstances,
Citizens are forced to adopt the father of the nation Gandhiji's famous and effective noncooperation movement by letting the government install the RWH and collect the dues
as land revenue (the mode of recovery as per law) which can be litigated at a high
inconvenience to government and BWSSB.
While we are  understandably shaking at their threat of disconnection of  daily water supply,we are also looking forward to the how of their implementation of stopping sewerage services.
They stop antagonizing large sections of the populace unnecessarily. It is cutting off the nose to spite the face.

What is the contribution

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What is the contribution these unfortunate's can make for the bludgeoning city and its water problems?

Unfortunates owning 60x40 sites in Bangalore? Hmm... I wonder what they will call the hutment dwellers. Gifted?


Dear IDS, In a democracy all

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Dear IDS,

In a democracy all are equal, fortunates and unfortunates. The tax paying unfortunates have been subsidizing even the hutment dwellers for their electricity, water and civic facilities all these years. So called hutment dwellers you seem to sympathize with all earn atleast  100 rs per day and each household income is about 10,000 per month in Bangalore since most are construction workers. My point is why should only the 60x40s or higher numbering 60,000 harvest the rain , why not the government which owns 60 percent of land around the city and receive funds from the UN projects do something more. Why not everybody? are you not tired of supporting the havenots all your life in some form or the other? gas,pds,water,electricity,ration subsidies? Everyone should be called upon  to harvest and save also, not just the 60,000. Just as an aside, it is already implemented in my property. I am fighting against the autocratic behaviour.

RWH - Set an example

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residents of 40x60 and above property owners old residents of Bangalore into installing rainwater harvesting apprears arbitrary and capricious. What is the contribution these unfortunate's can make for the bludgeoning city and its water problems?

If people who are well off, living in houses on 40' x 60' or larger plots question the need for them to employ RWH as a means to conserve water, what can be expected from those that live in slums & hutments ?

Let every one take responsibility not select 60,000

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My objection is  to the illegal, unauthorized,illogical  methods BWSSB is using for enforcement.

I have already implemented the RWH in principle- I donot want to pay the BWSSB engineer and his authorized contractor for a certificate. When things run on the basis of such certificates I am sure you know as well as I do that the RWH compliance will be only on paper.

Why not make it every house holder? why not club 2 site owners of smaller size? After all they also get rain water and infact it would encourage  the smaller houses to have atleast  a 3x3  open earth! everything is built up and concreted.

Why should not the meter reader who comes everymonth be permitted to certify compliance? Why burden the consumer?

Why have not rules been brought out for controlling the indiscriminate sinking of borewells which is one of the major causes for depletion of the water table after 25 years of the problem coming to their notice?

Are you one of the householders required to shell out for RWH or 30 percent educated, or 5 percent tax payer,  or  well off'  you  would  have many objections to  carry  all the ills  and ails of the other seventy percent.

They dont have to pay taxes, utilities, power, but get to live in an upscale address.  All the "benefits"  of "city" life they get is from your(?) and my hard earned money.  That goes to subsidize food, schooling and anything else government provides them in their name from your money.

After sixty years of giving "free" rides to the "unfortunates" slum dwellers and uneducated,

I object to hauling  the donkey cart, so they can have cell phones, radios cable TVs two wheelers, alcohol etc on your and my hard earned money.

Why should not the meter reader who comes everymonth be permitted to certify compliance? Why burden the consumer?

 Instead of creating awareness and cooperation. No one will have problems with prospective rules. But to selectively apply the rule to some 60000  old households arbitrarily, retrospectively is undemocratic and illegal. I dont know whether you have a porperty for which you have to make these alterations to "suit" BWSSB officials and the "authorized" contractors.
Have you any idea how much of BWSSBs revenue is drained by the illegal connections?

BWSSB should plug all the loop holes. How much can 60,000 houses save. Seeking voluntary compliance is always a better democratic way and supposed norm in a SIXTY years independent India.

They just sell their votes for a saree,drink, 500 rupees etc and tilt your democracy in their favor each and every time. Democracy becomes the mockery that you can see in every state every day.

Now a days you cannot get any of the villagers to do a day's honest work even by paying because under the Rozgar yojanas each household gets one job, which they get paid doing nothing.
That is why labor contractors are bringing employees from Bihar orissa west bengal etc.

All I want is democracy to be fair to one and all, not be based on the economic/educational status or the burden of the mass be borne by the educated or well off sixty years after independence.

 But to selectively apply the

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 But to selectively apply the rule to some 60000  old households arbitrarily

This I dont understand also, how the 60000 was arrived at, I would think it applied to all of Bangalore, including govt institutions

Seeking voluntary compliance is always a better democratic way and supposed norm in a SIXTY years independent India.

Sorry doesnt work, there needs to be nothing voluntary if it applied to all of Bangalore. It was voluntary so far how many have got it done?

Now see the arbitrariness

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The 60,000 is BWSSB figure of the 60x40 and above fraction of the  160,000 preexisting connections. The exempt 100,000 connections based on plot size is the vote based arbitrariness.

I have absolutely no issues with the value of RWH or the need to conserve water or to recharge depleting water table on an aggressive basis. If one has lived sixty years in post independent India it soon becomes obvious.

Voluntary or compulsory most of the governmental and public efforts are just an effort without anticipated returns. But I will participate in it as long as everyone irrespective of economic, or vote considerations is a party and government cracks a legal whip.

Disconnection of Sewerage and Water? Give me a break.

Microbiological potability of harvested rain water

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I saw a question on the potability of harvested rain water.
One short answer,microbiologically speaking  it is no safer or unsafer than BWSSB supplied water.
Escherichia coli count - coliform count- is an index of fresh human fecal contamination.
Waterborne Gastroenteritis outbreaks regularly occur in many parts of Bangalore especially around summer by water line contamination by leaky sewer lines or even open air defecation system adopted in the city.
 Even if the BWSSB minister Katta Subramanya Naidu blows hot  against water tanker services and  wants you getting sick only on BWSSB water.
The fact is these services thrive due to BWSSB inefficiency, inability to supply regular water.
However no matter how concrete the evidence,  I remember the photographs had floating feces, worms, insects and even a snake- BWSSB   labs invariably absolve them.
Have you ever heard of any postmortems holding an authority responsible or negligent?
Chemical potability is a different  problem especially because even though the roof is spotlessly clean, with Bangalore air being loaded with 1500 Tonnes perday of petroleum pollutants, the expected pristine purity  of rainwater is in  serious question.
Operation successful patient dead kind of retrospective consolation.
 And one negative test is no future guarantee.
 If you were to depend on a microbiological test result before you drank the water you would have to wait  24 or 48 hours.
If you need to drink the harvested rain water- I wonder why anyone would need to do that since even BWSSB supplies some water and bottled 50 ltrs- a weeks supply for a family-   are reasonably priced.
Microbiological potability is far easier to accomplish.
Virtually 100 percent safety level can be achieved by boiling  before  drinking  even the most contaminated water for about 4 minutes.
We have been using solar heater water straight for over 15 years without any adverse microbiological consequences like Gastro intestinal tract infections.
Testing the Microbiological potability of  water is  only hindsight value.
Anyhow, the RWH pales in significance in the intense threat of world exhausting its petroleum reserves by 2035, , 800 crores per year spent by bangaloreans on breathing disorders by 1500 tonnes perday noxious fumes spewed into Bangalores atmosphere, sound  pollution related illnesses while  each honk affects 8000 lives and violates supreme court mandated max noise level of 65 db by atleast 25 db,  800 vehicles crowding the 4500 km fixed road legnth and width- all controllable immediately with existing laws without any expense to anyone, with immediately palpable results.
Recall the peace and quiet of Bandh days?

popularizing rain water harvesting.

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I see a lot of discussion on rain water harvesting.  But this discussion should not be limited to people who subscribe to praja. Can praja do something whereby people owing houses and buildings in Bangalore (to start with and later to other areas including rurual areas) are educated about rain water haravesting whereby the ground water gets recharged and there will be abundance of water for generations to come.  Can praja popularize rain water haravesting so that people voluntarily adopt rain water haravesting for recharging the ground water.  many people feel that it is very expensive and further peopel are of the view that ground water would not get recharged by doing rain water haravesting.  Thank you.