Bangalore Environment Trust Newsletter, August 1997

Sat, 03/03/2007 - 19:59 admin



Rainwater Harvesting

INTRODUCTION: Bangalore has a major drinking water supply problem. This is due to a combination of an exploding population and the distance of any major perennial source of supply. Water therefore has to come from the river Cauvery from a distance of nearly a 100 kms. It has also to be pumped up 1600 ft because of Bangalore's altitude.
Sustainable water supply in a city's context is defined as being able to ensure consumption demands from within the catchment area and water basin within which the city is located. If water has to be transported from another basin then it cannot be sustainable.
Options which are being explored to make water supply sustainable include demand management through pricing, recycling of used water after treatment, charging of ground water table through percolation tanks and lakes etc.

ROOFTOP RAIN WATER HARVESTING: One significant option which has not been extensively explored so far is that of rooftop rain water harvesting. This paper seeks to look at the possibilities and describes one such experiment in the Bangalore context.
Thanks to extensive data maintained on meteorological conditions of Bangalore, information on rainfall data is available for over more than 100 years. The mean annual rainfall for Bangalore is 859.60 mm received over 57 rainy days. This suggests a significant quantum of rain and also speaks about a distributive spread.

Bangalore has three different rainy periods covering 8 months of the year. June to September is the principal rainy season where about 54% of the total annual rainfall is received with 34 rainy days and a mean rainfall of 496 mm.

October to December is the North-East monsoon period with a mean rainfall of 241 mm in about 14 rainy days.

In April-May the mean rainfall is 156 mm and the number of rainy days is 10.

THE SYSTEM: A very simple system is adopted for rooftop rainwater harvesting. The entire roof area is made to act as a rain collector. The roof slopes towards rainwater down spouts which have a wire mesh at their mouth as a grit and leaf separator. Water from these rain water spouts is lead down to ground level and made to pass through a box which has charcoal and sand. This acts as a filter. The filtered water is then stored in a sump of about 2000 litres capacity. As and when required, the rain water so collected is pumped up into an overhead tank of about 1000 litres capacity and used for all forms of domestic consumption.

OPTIONS: Collection of rain water can be done either at the roof level itself, in ground level tanks or in underground sumps. In Bangalore underground sumps are a common feature in every house and therefore appear to be the best option to store rainwater.

Rainwater harvesting has the maximum efficiency and effectiveness in single storeyed or double storeyed independent houses. The system is best applied for new constructions as adequate planning becomes possible in the design of the system. The costs of collection and storage can also be easily merged in the construction cost and no significant extra cost is entailed. Retrofitting to already built houses is also possible if any owner is so inclined to adopt the system.

COSTS INVOLVED: For a house under construction rainwater pipes and sump is usually already included as part of the construction. Additional cost involved for rainwater harvesting would be in adding capacity to the sump. This would be about Rs.4500/for a sump of 1500 litres capacity.

For a house to be retrofitted cost would be in the range of Rs.4500/- for additional capacity to the sump and about Rs.1500/- for additional pipes.

QUANTITY OF RAINWATER COLLECTION: In Bangalore, given .a mean rainfall of 859.60 mm and assuming a loss of about 10% due to evaporation and removal of dirty water during the first rain, quantum of water that can be collected for different roof areas would be:

As can be seen from the above table, a house with about 100 sq mt roof area (approx. 10 squares of construction in local terminology) would be able to collect 77400 litres of water.
For a family of 4 persons, with an average domestic consumption of 90 litres per person per day, About 215 days of water supply per year can be available through rainwater harvesting alone.

PRECAUTIONS: some nominal precautions are called for during rainwater harvesting including keeping the rooftop clean, free from leaves, twigs, bird droppings etc; not drying clothes with detergent laden water which may drip on to rooftop and mix with rain water harvested; not strong insecticides, pesticides, glass, oil etc which may mix with rainwater with harmful effects; not washing the roof with soaps and detergents; keeping the sump airtight and closed so as not to allow fly and mosquito breeding

 CONCLUSION: Rooftop rain water harvesting offers a possibility as a supplement to domestic water supply requirements and in conjunction with adequate demand management systems such as low volume flush, efficient taps and showers etc can considerably reduce the burden on city level water supply networks.

The system is also economical, environment friendly and individually manageable leading to self reliance. The option should be effectively used especially by new house owners and builders recognising that water is a finite resource which should be judiciously and efficiently used.

We have personally used the system at our residence since about 2 years and are convinced about its advantages. For persons interested, further details about rooftop rainwater harvesting can be obtained from

264, VI Main, VI Block,
BEL Layout, Vidyaranyapura,
 Bangalore - 560 097 Ph.8382435

R Vishwanath
Chitra Vishwanath

A Case for Padestrian Rights in Bangalore's Traffic Jungle

Pedestrian safety seems to be the least on the list priorities of city's traffic planners and managers. The oversight is all the more striking if one considers the fact that pedestrian -casualty has been witnessing an alarming rise over the last few years in Bangalore. It constitutes a sizable proportion of road accident victims in general. According to one study, in the year 1994, 2200 pedestrians were seriously injured and 242 were killed in road accidents. Also pedestrians seem to be the worst affected by vehicular air pollution, especially f by the smoky exhausts from heavy traffic vehicles, as they are present for a longer duration on roads than others; any proposal to improve the conditions for road safety and comfort has to incorporate measures to mitigate vehicular air pollution. And, to make matters worse they are often seen by other road users as a necessary evil! Exposed to the poisonous fumes, abused by vehicle drivers, elbowed around for lack of space - they exist as the silent suffering majority in the roads.

With the exception of traffic infrastructure facilities, everything in the city has been recording fast growth. Inadequate urban public transportation system, pothole - humps filled roads, steep rise in motorised vehicular traffic, poor implementation of buildings bye-laws, are by and large the reasons usually discussed in seminars and conferences with regard to traffic congestion and air pollution. With no spokesperson to articulate their concerns, pedestrians and cyclists are left to fend for themselves.

In this context, it is worthwhile to focus on two most fundamental rights of pedestrians: Right to safety and Right to comfortable walking on the roads. The enabling provisions that guarantee both the rights are almost the same. Infrastructure problems do contribute to pedestrian woes only to some extent. However, two of the most simple but important issues that need urgent attention are footpaths and pedestrian crossings.


On some roads, footpaths are missing - a case in point is Lavelle road; While on others, they are either dilapidated or dying a slow death, due to poor maintenance and various kinds of encroachments. Uneven surface, existence of a wide variety of poles, pits, junction boxes - all of these discourage pedestrians from using footpaths, leaving them exposed to dangers. Encroachments by hawkers, venders, vehicles and religious structures have reduced the space for pedestrian movement on the footpaths. Clearing the footpaths of encroachments is also a social problem. When it can happen in Calcutta, why not in Bangalore? Political will is the key. Hawkers and vendors need to be adequately rehabilitated and strict rules must be enforced to see that no structures obstruct pedestrian traffic.

Pedestrian crossings

  1. Subways, footbridges and mini flyovers
    At present facilities for pedestrian crossings are grossly inadequate. As it is there are very few subways, footbridges / flyovers, but even these are not fully utilised by pedestrians. But for the presence of lathi wielding traffic cops, pedestrians are never inclined to use these existing facilities. Some cases in point are:

    1. The subway and the pedestrian foot bridge that connect the Bangalore Bus Stand and the City Railway Station; In front of railway station, on Tank Bund road, it is a common sight to observe men, women and children struggling to jump across the five feet tall barricades to reach the railway station from the bus stand side.

    2. The mini flyover on Kempegowda Road appears like a ruined monuments built by Kempegowda, the founder of Bangalore.

    3. The subway near K. R. Market seems to be an extension of the market itself.
      It is needless to say that we need iuerbridges and mini flyovers at some selected points especially near hospitals and schools. But pedestrians have to change their `short-cut' behavior if they want to demand for more.

  2. Zebra crossings at the junctions
    At present most of the junctions have signals. However, for pedestrians, its a test of patience as they have to wait for a long time for the green signal. Having waited thus long, they have to virtually run to reach the other side because the signal time is too short. At some junctions where there are railing barricades that separate the road and the footpath, the zebra crossing becomes very crowded due to signal-junction box, signal pole and so on. A case in point is Cauvery Emporium Junction on M.G. Road - In fact, one end of the Zebra crossing was blocked by barricades on one of the roads at the junction. The police were quick to rectify when it was pointed out.

Other issues which need to be considered are

  • Creation of some pedestrian zones in market areas, where there is a total ban on vehicular traffic.

  • Improving the trauma care facilities for accident victims.

  • Setting up Pedestrian Aid Posts at select locations to aid and assist the foot-path commuter.

Last but the most important - education for behavior change amongst all the road users including pedestrians. Ultimately the responsibility for ensuring one's safety rests with one self, which calls for a certain sense of discipline and change of existing attitudes. Life is too precious to be lost on roads.


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