Rainwater harvesting

This is a hot topic these days and is indeed now more relevant than ever!

I would like to share with you my own experience, which started as an experiment and it really worked.

Those days I was working in the color television factory of a leading brand based out of Bangalore.

All the borewells that we had tried in our factory area were failures. From many years, we had been purchasing several tanker loads of water each day from a private contractor to meet our needs.

A few years ago, we implemented an environment management system as per ISO14000 standards. This required us to identify and implement a few environment management projects as an initiative to improve the environment around the factory.

This was when we hit upon the idea of trying to harvest the rainwater from the roof of our factory building. The factory building itself was rather huge with a rooftop area of almost 7000 square metres. Bangalore has an average annual rainfall of just under 1000mm. This meant that the rain water falling on our factory building alone was approimately 7 million litres a year and to think that all this was going waste and running off into the drains!

A team was formed. We conducted a survey and found that all the rain water down pipes of the building were letting the water into a cement channel at the foot of the building, which ran all around the building. Storing the rain water for use would have required building a very large underground sump. This idea was discarded as it was too expensive. Luckily, we found that there was an old, dry open well located not far from (< 20ft) the channel carrying rain water. This suited us very well. All that was now required to be done was to connect the rain water channel to the open well with a large diameter plastic pipe with a filtering arrangement to trap any leaves and other unwanted debris.

This was four years ago. Recently, we conducted a water availability test on our factory premises using a hydro geologist. When the results came out we were pleasantly surprised to learn that there were no less than four points with a potential water availability of between 1500 to 2000 gallons per hour! We are convinced that this result was achieved because of ground water recharging over four years and the consequent raising of ground water levels.

A similar experience was narrated to me by an acquaintance, who was a Managmement Committee member in the residents association of a gated community in south Bangalore. One of the borewells in the complex, which was 800 feet deep had gone dry. So they decided to drill another borewell at a distance of about 20' feet from the existing borewell in order to recharge the dry borewell. The new borewell was drilled to a depth of 300'. Rainwater was channelled and let into this new borewell through a filtering arrangement. Within a few months the old dry borewell had completely revived and now yields plenty of water!