ALN logo; link to Arid Lands Newsletter home page No.56, November-December 2004
Water efficiency I: Cities

Rainwater harvesting in urban areas: The Chennai experience

by Sekhar Raghavan

The Indian city of Chennai receives abundant rainfall during the monsoons but is still water-starved due to over-exploitation of groundwater. One possible solution, as outlined here, is to implement widespread urban rainwater harvesting for aquifer recharge.


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Rain is the predominant source of all the fresh water on this planet. Harvesting rain is thus one crucial means of sustaining both our surface and sub-soil water sources. That this has been historically well understood throughout rural India is evident from numerous traditional water harvesting systems put in place long years ago and still in operation. On the other hand, urban India to date has not only taken water for granted but has exhibited little interest in rainwater harvesting (RWH), despite its potential to help sustain groundwater sources in the urban milieu either indirectly (by using harvested rainwater to lessen the need for pumping groundwater) or directly (by injecting the harvested water into the aquifer).

Yet, 60% of India is expected to be living in towns and cities by 2025. Municipal authorities are finding it more and more difficult to meet the water needs of this bourgeoning urban population. A classic example is the coastal city of Chennai (Madras), one of the four major metropolises of India and the capital of the state of Tamil Nadu. Inadequate supply of municipal water over the last two decades has forced the populace to relentlessly tap groundwater for its needs. This over-exploitation has resulted in the sharp depletion of the groundwater table and to deterioration of its quality as well. In Chennai's coastal suburbs in particular, seawater has already intruded into the coastal aquifers, rendering groundwater quite saline.

Many other cities, both in India and elsewhere, are already facing a similar situation or heading towards it. India, with its bounteous monsoon rains, can substantially alleviate the problem by artificial recharge of the groundwater in areas like Chennai, where the underlying sandy soil and aquifer structure is suitable for such purposes. That is, after rainwater has been gathered by efficient and cost-effective RWH structures throughout the city, it can be systematically injected into the soil by means of equally cost-effective wells and other infiltration structures. Urban rainwater harvesting is of a more recent origin than rural water harvesting; new designs will have to be developed for the urban context, particularly for RWH systems that are primarily concerned with aquifer recharge. But progress made to date in Chennai indicates that such changes are indeed feasible, cost-effective, and potentially quite effective for other similar urban locations.

Promoting urban RWH involves three components:

  1. Education: Creating awareness regarding the importance of rainwater harvesting, both for immediate uses and also for sustaining the water table in the long run.
  2. Implementation: Designing and providing programs to help citizens implement rainwater harvesting in an efficient and cost-effective manner.
  3. Evaluation/Research: Carrying out studies on:
    • the nature of the sub-soil in different city neighborhoods and its capacity to absorb large quantities of injected rainwater;
    • the effectiveness and adequacy of various types of RWH structures; and
    • the post-monsoon impacts on the quality and exploitable quantity of groundwater in places where RWH has been implemented.

Role of individuals and NGOs

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In order to carry out these three objectives, the author initiated a door-to-door campaign in 1995 in two of Chennai's coastal suburbs, Besant Nagar and Valmiki Nagar. Both the quality and the quantity of groundwater in these localities were excellent till about 10 years back. But, as construction proliferated, use of groundwater increased steadily even as the amount of bare soil available for direct absorption of rainwater shrank substantially. As a result, the groundwater table level in these areas steadily went down.

The campaign's primary objective was to create awareness about the importance of rainwater harvesting. It was explained to the residents that implementing rainwater harvesting in these sandy-soiled areas would be very simple and cost-effective as well as being an excellent tool for preventing seawater intrusion into the aquifer. This is especially germane in cities like Chennai, where many people live in multi-story apartment complexes that depend on individual wells, rather than a municipal water system, for both potable and non-potable water uses. However, the concepts being new, the initial response to these ideas was none too encouraging; residents were reluctant to invest in rainwater harvesting systems. It took almost three full years and the help of the print media -- especially neighborhood newspapers -- to convince the residents of the need and relevance of RWH in a city like Chennai.

In order to accelerate these activities, a few like-minded people formed the Akash Ganga Trust in January 2001. Taken together, "Akash" ("sky") and "Ganga" (the perennial river Ganges of North India, believed to have descended from the sky) mean "water received from the sky," or rainwater. On August 21, 2002, the Trust launched Chennai's Rain Centre, inaugurated by the Honorable Chief Minister of Tamil Nadu. The Rain Centre, the first of its kind in the country, is a one-stop information and assistance center on rainwater harvesting. The initial seed money for the center came from a few non-resident Indians living in the U.S. Further support, in the form of resource material, was provided by the Centre for Science and Environment, an NGO headquartered in New Delhi. The state government of Tamil Nadu is also one of the co-sponsors of the Rain Centre.

In addition to Akash Ganga Trust, a few other NGOs like Exnora, Rotary Clubs, Lions Clubs and INTACH (Indian National Trust for Art and Cultural Heritage) have also been playing an active role in promoting RWH in Chennai. Particular mention must be made of the efforts of Rotary International District 3230 in renovating and reviving seven temple tanks for use in artificial recharge of the harvested rainwater, besides creating awareness among its members.

The Rain Centre has been involved in all the three thrust areas defined above (education, implementation, and evaluation/research) since its launch almost two years ago. The Centre, which is open to all, charges no fee for its services to the citizens. Its activities, carried out thanks to the funds received by the Akash Ganga Trust through donations, are summarized below.


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Thumbnail link to Figure 1
Link to Figure 1, ~35K

  • Working models in the Centre demonstrate RWH both from flat and sloping roofs and from ground surface runoff.
  • Different types of actual RWH systems have been installed in the Centre's premises, e.g.:
    • diversion of rooftop rainwater into plastic tanks above ground, for immediate use;
    • diversion of rainwater into below-ground masonry cisterns equipped with sand filters to enable immediate use of the water, and with overflow directed to traditional dug wells for use and recharge purposes;
    • trapping of surface runoff on individual properties through means of shallow trenches dug and directed in such a way as to direct the trapped water into a recharge well.
  • These RWH systems can be demonstrated "live" by simulating rainfall to enable visitors to understand better how the systems operate and how simple the methodology is.

Thumbnail link to Figure 2
Link to Figure 2, ~34K

  • A number of large sized colorful poster panels highlighting the value of water and the importance of RWH are on permanent exhibition in the Rain Centre.
  • Video film shows on RWH are presented periodically for the general public.
  • Resource materials like booklets, posters etc. have been prepared in English and Tamil and are distributed at a nominal cost. The posters have also been pasted in public places, where people tend to assemble like the divisional and zonal offices of the Municipal Corporation and Chennai Metrowater, post offices, marriage halls, bank branches, and school and college notice boards.
  • A publicity button was prepared and worn by Trust members in order to publicize RWH. A sign saying "RAINWATER HARVESTING DONE IN THIS PLOT" distributed to people who had implemented harvesting in their respective premises, also generates publicity when it is fixed on the gates so as to attract the curiosity of passersby.
  • During the last couple of years, students from several schools and colleges have visited the Rain Centre and learnt about RWH. Key persons from the Centre have also visited several institutions both within and outside the city and the state, to give talks, video presentations and exhibitions about RWH.
  • Several NGOs, working in both water sector and other areas have visited the Rain Centre.
  • Seminars and workshops have also been organized in the Centre.


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Free, site-specific advice is provided to all those who want to implement RWH systems in their respective premises, including academic institutions, offices, industries etc.

In December 2001 and August 2002, the Centre conducted two training workshops in RWH, specifically aimed at plumbers. Advertisements in both vernacular and English language newspapers requested plumbers to apply, with the incentive of having jobs after the workshops. The trained plumbers were thereafter sent to different areas of the city to advise residents on RWH design and implementation costs. After the state government made RWH compulsory in October 2002 (as explained later in this article), several more newspaper articles about RWH also mentioned the Rain Centre with its offer of free advice and assistance through trained plumbers. During the following year the Centre received several hundred calls requesting such help.

With the assistance of these trained plumbers, RWH was directly implemented in more than 1000 premises; an equal number of residents were provided with advice on getting it done with their own plumbers. Though this may appear to be a small fraction in the total number of households in Chennai, it has had an important "ripple effect" in spreading the correct methodology.


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From October 2003 through January 2004, the Centre surveyed a local residential colony to ascertain the adequacy of the RWH structures that had been installed to comply with the law, described in more detail below, enacted by the Tamil Nadu government making RWH compulsory. In this survey, RWH systems were evaluated using the following criteria:

  • Completeness (whether both rooftop and driveway runoff had been harvested).
  • Apportioning of rooftop for different harvesting methods (thereby avoiding overload of any one system with subsequent overflow and loss of rainwater).
  • Proper design (taking into account the volume of water likely to flow through them and the nature of the soil in the area along with its capacity to retain the ingested rainwater).
  • Maintainability (Whether the design incorporated features allowing for periodic maintenance of the structure).

The colony chosen for the survey, Gandhi Nagar, comprises 309 contiguous plots occupied either by independent houses or multi-story apartment complexes. The survey revealed that all but 2 of the 309 residences had installed RWH structures. However, only 30% of the systems installed were extremely well-designed; another 20% of the installed systems were adequately/reasonably designed, and the remaining 50% were not well designed. These poorly designed systems proved to correlate strongly with households whose residents were not convinced of the importance of RWH, but only installed systems to comply with the law.

Another survey examined how citizens are managing their water needs for both potable and non-potable uses, particularly in light of Chennai's current rain deficit. Results were particularly useful given the Rain Centre's interest in educating people about wastewater reuse and recycling, water usage and conservation, composting toilets, and so on. The findings, published in the local English newspapers, revealed that people are not only learning to live with less water, but also with different qualities of water for a) drinking and cooking; b) bathing and washing; and c) toilet flushing. However, due to failure of the northeast monsoon in Chennai during 2003, assessment of the post-monsoon and post-harvesting effects on quality and quantity of groundwater, for establishing the benefits of rainwater harvesting, was deliberately left out of the scope of the survey.

Future Activities

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Having created widespread awareness about the importance of RWH both in Chennai and throughout Tamil Nadu, the Rain Centre proposes to follow up by educating residents about potential problems that may result from RWH structures put up without the help of trained resource persons. Residents will also be helped in correcting and repairing any structures determined to be faulty. In addition, the Centre will continue to work with larger organizations towards effective implementation of RWH in their respective premises. Training workshops for plumbers will also be conducted regularly in future.

As another water conservation measure, the Rain Centre also proposes to promote awareness about the importance of water reuse. Water that is used for bathing, washing clothes, vessels, vegetables etc., is generally referred to as "sullage." Currently, this sullage, typically 50 - 60 liters per day per person, gets mixed with sewage (water from toilets) and sent to sewage treatment plants for treatment. However, sullage does not need the degree of treatment that sewage does; it could be easily and economically purified of organic compounds and either directly reused or recharged into the groundwater. The Centre is committed to working towards policies and techniques that will promote this separate treatment and usage of sullage water and sewage water in future.

In addition, the Rain Centre is offering its help and expertise to set up similar centers in other cities in India and is also conducting a survey to select cities in other countries where RWH for large-scale groundwater recharge would be relevant.

The Trust is also interested in setting up, at its own cost, RWH systems in charitable organizations such as old age homes, orphanages, homes for the physically and developmentally disabled, and homes for destitute women. Since these are basically service organizations depending on donations from concerned individuals and corporations, they are often unable to afford the financial outlays needed for the installation of RWH systems. At the same time, these organizations require large quantities of fresh water both for potable and non-potable uses; therefore, they can have a very important role to play in sustaining local groundwater sources through the practice of RWH.

Role of the government and government agencies

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Since May 2001, the government of Tamil Nadu has promoted awareness about RWH throughout the state by putting up posters inside and on the back of buses as well as in public places; preparing and distributing pamphlets and brochures in Tamil and English; and producing and screening videos on RWH. In addition, a publicity van was specially made by the Chennai Corporation to propagate RWH in various localities of Chennai. Similar Rain Centres were started in two more Chennai neighborhoods, one by the local-level and one by the state-level water authorities. Others were started in the offices of the District Administrative heads of all the 27 districts of the state.

At the national level, school and college students have been involved in RWH awareness-raising campaigns in small towns through the National Service Scheme (NSS), a government-supported activity in colleges and polytechnics. They have also been involved in rallies carrying placards about the importance of RWH.


The Tamil Nadu government enacted a law in October 2002, followed with an ordinance in June 2003, making the implementation of RWH systems compulsory in all existing buildings in the entire state of Tamil Nadu by October 11, 2003. The law mandates that "waste water from the bath and wash basin shall be treated by organic or mechanical recycling and taken to a sump for onward pumping to an exclusive overhead tank for use in toilet flushing. Any excess shall be connected to the rainwater harvesting structures for groundwater recharge."

Further, Tamil Nadu's Groundwater Regulation Act of 1987 has also been amended to include the power to grant or refuse groundwater licenses. Use of groundwater for gardening, for private swimming pools and for non-potable uses by industries has been banned. Those who are found guilty will be fined Rupees (Rs.) 2000/- for the first time and Rs. 5000/- for the second time; these substantial amounts are calculated to have a strong deterrent effect.

To show that it not only preaches but also practices, the government also issued orders to all its departments to implement RWH in buildings belonging to them. The Chennai Corporation has implemented RWH in public places like roads that get flooded during monsoon, schools, parks and their staff quarters.

The Hindu Religious and Charitable Endowments Department, another state government department, has taken up desilting of the 39 temple tanks within the city and hundreds of them in the entire state and has made adequate arrangements for directing rainwater from adjacent areas into the tanks for gradual infiltration into the groundwater.

Chennai's Metrowater Department, which is responsible for operation and maintenance of the entire water and sewer system within Chennai, has conducted free workshops on RWH implementation techniques for all interested. It has especially focused on training for unemployed diploma holders, who are subsequently listed as resource persons for carrying out RWH in houses/flats. To date, however, the government has not carried out any surveys, such as those conducted by the Ashoka Ganga Trust, to ascertain the efficiency of the RWH systems implemented by Chennai residents.


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Chennai city, like most of the other large metropolitan areas in India, is water-starved but not rain-starved. All we have to do is to make sincere attempts to harvest every drop of water that falls on our heads before thinking in terms of mega projects like interlinking of rivers or desalination. It would not be wise to allow rainwater in amounts equaling the city's one-year water requirement to escape into the sea monsoon after monsoon, while at the same time talking of desalination. Furthermore, we cannot overemphasize the danger that excessive pumping of groundwater from coastal aquifers will result in seawater intrusion into those aquifers, creating permanent and irreversible damage to the water supply. Thus rainwater harvesting, while important in every major town and city the world over, is particularly important in coastal cities.

The need of the hour is to spread the message of RWH as widely as possible, from neighborhoods, to cities, to entire countries. This, I am convinced, can best be achieved by carrying out awareness-raising campaigns and by setting up more Rain Centres across the length and breadth of every country as a mass movement. Cities throughout the world, which are water-starved but not rain-starved, will have to be identified and selected for this purpose. I would like to conclude by emphasizing again that water harvested is water produced. Our slogan for the future should be: HARVEST RAINWATER LEST WE PERISH.

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Editor's note: On 26 December 2004, Tamil Nadu and Chennai were hit, like so many other locations in Asia and Africa, by the devastating tsunamis resulting from a powerful earthquake off the coast of Sumatra. In light of this natural disaster, Mr. Raghavan offers the following addendum to his article:

In India, the coastal districts of Tamil Nadu were very badly hit by the tsunamis; more than 10,000 people have died. A particular concern for the Rain Centre is how the tsunami may have affected the area's coastal aquifers:

  • The large quantity of seawater brought in by the tsunamis could have receded back to the sea immediately.
  • The seawater could have flooded the coastal areas but remained above ground, eventually evaporating. (This would happen in areas with rocky or clayey beaches).
  • The seawater could have percolated into the soil either rapidly or within a reasonable amount of time. (This would happen in areas with sandy beaches like Chennai).

The last possibility is the most worrisome in terms of possible effects on groundwater. The amount of damage would depend on the quantity of seawater percolating into the aquifer, the pre-tsunami quality of the groundwater and the depth of the water table.

In order to conduct a survey to quantify the tsunami's potential effects on groundwater, pre-tsunami baseline data would be required, including the depth of the groundwater table and the quality of the groundwater. For Chennai, few baseline data are available except from the few government monitoring wells, which are monitored monthly. We at the Rain Centre propose to collect these data from the concerned government department and monitor them for at least the next year, in order to determine what effects the tsunamis may have had on the local groundwater.

If it proves that the water quality of coastal aquifers has been adversely impacted by the tsunami, RWH can help reverse the damage: through focused recharge of such aquifers with pure, harvested rainwater, the brackish water will be diluted and the water quality will be restored to that of pre-tsunami days. To the extent that such steps are required, the Rain Centre will support them to the utmost of its ability.

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Author information

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Dr. Sekhar Raghavan, an Ashoka Fellow, is Director of the Rain Centre. He can be reached for comment by email at or by post at the Rain Centre address:
4, 3rd Trust Link Street,
Chennai 600 028, INDIA

Additional web resources

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Akash Ganga - RWH: Rain Centre
Web site of Chennai's Rain Centre

Harvesting the rains!
This 2002 article from India provides more background on Akash Ganga and the Rain Centre.

This web site from Chennai Metrowater contains extensive information on rainwater harvesting.
Produced by the Center for Science and Environment, a New Delhi-based NGO, this site focuses on rainwater harvesting in India but also contains information of interest to rainwater harvesting practitioners elsewhere.


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