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How pure, roof RAINWATER?
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"The rainwater in the storage tanks is an ideal breeding ground for bacteria and fungi" - Prof. N. P. George.
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RAIN WATER harvesting is the subject in vogue today. On TV, on stages, and myriad publications, rain harvest is discussed, and creative minds bring in different ways of making the rain last and serve the causes of an ever-increasing humanity at large. But here's a voice that dares to be different, that is sceptical about the ways being popularised to harvest rain for drinking water purposes.
Prof. N. P George, a chemistry buff, an academic, a founder member of the Gandhi Peace Foundation in Kochi Centre and a votary of much that is organic, is loud and clear about his views, opposing the present method of rain harvesting promoted by the Government and NGOs: collection of rain water falling on roofs and slabs, through pipes and preservation in closed storage tanks made of cement or Ferro cement.
"The construction cost of a permanent tank and the cost of drains and conduit pipes work out to at least Rs.10, 000-15,000 for a 10M3 unit, equivalent to 10,000 litres of water storage. For an average home consisting of four members, the average daily water consumption speculated is 500 litres, which means water for just 20 days. For a tank of one meter height, the land to be spared is 10M2 which means over a quarter of a cent which is unaffordable for households in less than 5 cents of land," Mr George says. He explains further, " Rain water is naturally distilled water, ultra pure at the point of origin. But it reaches the earth, passing through a number of contaminant gases in the atmosphere as also dust and carbon particles. Atmospheric nitrogen and oxygen chemically combine during lightning to form nitrous and nitric acid. These acids get neutralised in the soil bases forming nitrates, which fertilise the soil. But water collected directly from rooftops necessarily remain contaminated by these acids." In the industrial belt of Kochi, especially, the atmosphere carries large amounts of sulphur dioxide, ammonia. Besides the gases released by the many industries and emissions from vehicles, including lead particles also contribute heavily to atmospheric pollution, contaminating rainwater on its downward journey to earth.
The rainwater that gets collected in the storage tanks directly without being subjected to solar sterilisation is an ideal breeding ground for bacteria and fungi. But not so well water, points out Mr George. The rain water accumulates in the well after its acidic components are neutralised by the soil bases and the suspended impurities filtered out by the earthen bed .
"Our earth itself is a mega storage tank," contends Mr George and points to the example of the Sarang Hills in Attappady, where bunding and humus, the twin strategy has reaped dividends, storing rain water the natural way. Cutting down leaves and branches of trees enhances the organic matter status of the soil. Dung is spread, so that worm-burrows appear. Each burrow, with the castings; act as a funnel that drives the rainwater down, averting water stagnation and over flow. The water that is driven to a 3-metre depth by the burrows will be relayed down by the natural crevices and the voids left by the decaying roots of deep-rooted tress. Thus aquifers get recharged.
The underground water rises to the soil surface by capillary action and proper mulching will save the loss of water by sun's heat. "Human activity loosens the top soil just 5 to 6 inches deep, but the earthworms burrow up to 10 feet, facilitating the deep penetration of air and moisture for the soil microbes that really make the soil fertile," Mr George winds up his case for natural rain harvesting.
PREMA MANMADHAN
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Metro Plus
Bangalore
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Kochi
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Visakhapatnam
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