The present day scenario calls for a move at the grass root level to conserve the most important resource on Earth-WATER. Water comes to us in the form of rain, which has been celebrated in Indian art and poetry through the centuries. At present, the specter of empty pots lining the streets of our towns and dry wells in the villages of the country are a harsh reminder that something needs to be done.
At the rain center, a project managed by the Aakash Ganga Trust, an NGO based in Chennai, they try to underline why rainwater harvesting is vital. In India, rain is the ultimate source of all fresh water. Rainwater fulfills all our personal needs, with the exception of desalinated water. People often believe that rainwater is different from ground water. This lack of awareness is what needs to be changed.
Why it is important?
Rainwater harvesting is all about collecting water when there is rainfall, for use during the non-monsoon months. Rainwater harvesting replenishes the existing ground water. During a typical monsoon in Chennai for example, it rains for two months for an average of 300 hours (of rainfall). So, unless you are careful in capturing this rainwater, you will be left with no ground water. The objective of rainwater harvesting is to ensure that not even one drop of rainwater is allowed to enter the sewage or flow onto the streets, but is, instead collected into some groundwater bank. Today rainwater harvesting is a buzzword in urban centers, whereas 15 years ago it was a relatively unfamiliar term. We are not surprised by this and believe it’s due to widespread urban development. In the past there were a lot more open spaces in cities, so rainwater harvesting took place naturally. Today, with the paving of garden areas, a high density of buildings and skyscrapers, paved pedestrian platforms and the absence of household wells, rainwater is prevented from percolating into the ground. This results in steady depletion of ground water due to indiscriminate digging of deep bore wells which do not get adequately replenished with rainwater.
Is it expensive? The rainwater harvesting set-up is a one-time expense and if done properly, could cost you between Rs. 3,000 to 5,000. For residents living in independent houses, the cost of rainwater harvesting would increase with the size of the building or house.
How to do your bit? The lack of fresh water is something that affects all of us, whether we are rich or poor. The fact is all human beings need fresh water for their survival. Nobody has the right to abuse the care and consideration of this vital natural resource and it’s up to us as citizens to be responsible and actively interested for something as indispensable as ground and fresh water harvesting, for our collective survival.
How to harvest rainwater?
The roof top method: One of the easiest ways to harvest rainwater is through the collection of good quality water if it falls on clean terrace areas. The rainwater is collected through drainpipes connected to an open well in the compound that would ordinary receive corporation water or ground water. If you need fresh water for immediate use, keep buckets and large vessels in an open area during the rains.
The absorption pit method: A percolation or absorption pit is a hand bore made in the soil and is filled with pebbles and river sand on the top. The depth of these pit cans be anywhere between four and eight meters depending on the nature of the soil. If the soil is clayey, the pit has to be dug to a depth at which a reasonably sandy stratum is reached. The diameter of these pits will be 25 cm (10 inches). A circular collection chamber with a silt arrester is provided on top.
The absorption well method: These wells are constructed using cement rings available in the market. The diameter of these rings varies from two ft to six ft. the depth to which these wells are dug depends on the nature of the soil and the diameter depends on the number of roof top pipes that are likely to be connected to each one of these wells. These wells are left unfilled and are covered with RCC (reinforced cement concrete) slabs of suitable thickness to facilitate free pedestrian and vehicular movement on the ground. Rainwater from the terrace is diverted to the existing open well using PVC (poly vinyl chloride) pipes through a filter chamber.