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A NEW BEGINNING |
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| Urban wetlands meet CSE initiates a core committee |
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IN FOCUS |
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| Null and void? A success story? The flouride menace |
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CAMPAIGN |
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| Lake in news From the courtroom To save this tal Operation Baikal |
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INITIATIVE |
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| Stories from
Dewas Meerut meet Initiating change Sensitising regional media Doosra dasak Glimmer of hope History rewritten HLL harvests Water soliders The kiwi connection Exploring Ahmednagar |
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FACE TO FACE |
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| For
my home.... |
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TECHNOLOGY |
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| Bamboo-supari
pits Countering flouride Techno tit bits |
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| CSE'S LATEST DESIGNS | ||
| Meet the new
harvesters! |
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JAL YODHA |
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| T R
Sureshchandra Arun Mathur Shivanajayya K G Vyas R Ramani |
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NEWS FROM CHENNAI |
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| Recharge
maps Bank loans for RWH Harvesting in Nilgris The Vengaivasal model 'Water wisdom' in schools |
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JAL BIRADARI |
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| No to
bore wells Ghagara revived Jal bhai, Jal bahen |
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NEWS FROM GUJARAT |
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| Charting
future City's pride |
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NEWS FROM ABROAD |
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| Vol. 4 | No. 5 |
October-November 2002 |
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Indians, over centuries, developed a range of techniques to harvest rainwater, as a part of their daily lives. In this issue, we will concentrate on the urban rainwater harvesting techniques, while keeping rural ones for the next issue.
India has more than 250 million city dwellers.The water supply sector is faced with a number of constraints. Almost all the cities depends on groundwater as a major source. The result is rapid depletion. In addition, the problem of quality is getting grim. Problem of increasing salinity, nitrate, hardness, flouride is common.
Broadly, rainwater can be harvested for two purposes: storage for direct usage and groundwater recharge. If the number of dry days is less, than it can be used for direct usage like in Kerala and Mizoram . But it will not work in cities like, Delhi, where the recharge option holds water, as rains are for a short duration.
Suppose, a person has a roof with an area of 100 cubic meters and is getting 100 millimetres of rain - then, his rainfall endowment is 10,000 litres (l) and, the potential is 8,000 l.
Direct storage is a
well tested technique.The rooftop runoff is taken to storage containers. As per the rain
coefficient calculated above, 8,000 l of water can be used by a family of four members for
200 days. It will fulfil their drinking water needs. To prevent leaves and debris entering
the system, mesh filters are used. In some cases this rooftop harvesting system comprises
of commonly used storage containers like masonry or plastic water tanks. Some maintenance
measures like cleaning and disinfection are needed to ensure the quality of water.
Alternative to storing, rainwater may be charged into the groundwater aquifers. While some structures promote the percolation of water through soil strata at shallower depth (like recharge trenches, permeable pavements), others conduct water to greater depth from where it joins the groundwater (like recharge wells). At many locations, existing features like wells, pits and tanks can be modified, eliminating the need to construct afresh - reducing the cost.
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