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Anjali Prayag

BANGALORE, June 14

JUST think of this. If you have a rainwater harvesting facility installed in your house, one evening's rain for two hours is enough to give 8,000 litres of water, which will suffice a family of four for seven days.

With Bangalore having about 60 rainy days in a year, it is estimated that residences with a 100 sq m roof can gather about 97,000 litres of water per annum which will take care of the water needs for about 200 days.

And look at the cost factor. The pipes cost about Rs 15 to Rs 30 per running foot and the storage systems about Rs 2 to Rs 3.50 a litre and the bends and elbows between Rs 20 and Rs 75, bringing the total cost to Rs 4000-Rs 5000.

According to Bangalore-based rainwater harvesting consultant, Mr S. Vishwanath, "When people are spending 15-20 lakhs on the building construction, this cost is miniscule.''

Assuming a 20-year life period for the structure, the cost per kilolitre works out to less than Rs 4 a kilolitre making it extremely cost-competitive. City supplies have a production cost of Rs 15 per kilolitre.

The process of rainwater harvesting would encompass catching rainwater, directing it to an appropriate location and filtering it, if required, and storing it for use. Storage could be in tanks, sumps, ponds or lakes. Recharging of ground water is also possible.

Mr Vishwanath who started the Rainwater Club in Bangalore says in a study by the Karnataka Government, `A conceptual framework for rainwater harvesting for Bangalore', it was found that the city receives about 3,000 million litres per day of rainwater with an area of 1,279 square kilometres. Compare this to the nearly 1,500 million litres per day, which will be pumped in after the augmentation projects of the Bangalore Water Supply and Sewerage Board (BWSSB), now under construction.

Several residences, office complexes, schools and industries, about 1,000 in numbers, in the city are already reaping the benefits of this system. For example, the industrial unit of Escorts-Mahle-Goetze, located in Yelahanka, has a rooftop harvesting system for 1,280 square metres, which collects approximately 2.50 million litres of water. The system has been designed to collect about 62 million litres harvestable water. A cost of Rs 2.5 lakhs was incurred and when 62 million litres is collected, the savings will be to the tune of Rs 40 lakhs per annum in the water bills.

Similarly, the harvesting system at the Chemical Engineering Department in the Indian Institute of Science is saving about Rs 22,500 per annum for the Institute.

Realising the benefits of the system, the Bangalore Mahanagara Palike, has decided to adopt this technology in parks and gardens. Considering the fact that the city has 400 parks, the savings on water costs will be enormous. The Government is also considering making the harvesting system mandatory in all new construction projects (both residences and commercial).

But, says, Mr Vishwanath, instead of making it mandatory, the Government would achieve better results if an awareness campaign is started on the benefits of the system. "Concessions that were given for solar water heaters could be given here too.''

He feels this should be a people's movement rather than a Government initiative as the Government has too many responsibilities to fulfil.

So, how is he promoting the concept among Bangaloreans? "Through architects, plumbers, contractors and we have started a Web site www.rainwaterclub.org which provides all the information to the public.''

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