A NEW BEGINNING

 






Urban wetlands meet
CSE initiates a core committee

  

IN FOCUS

Null and void?
A success story?
The flouride menace
 

CAMPAIGN

Lake in news
From the courtroom
To save this tal
Operation Baikal

INITIATIVE

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

FACE TO FACE

For my home....

TECHNOLOGY

Bamboo-supari pits
Countering flouride
Techno tit bits

CSE'S LATEST DESIGNS

Meet the new harvesters!

JAL YODHA

T R Sureshchandra
Arun Mathur
Shivanajayya
K G Vyas

R Ramani

NEWS FROM CHENNAI

Recharge maps
Bank loans for RWH
Harvesting in Nilgris
The Vengaivasal model

'Water wisdom' in schools

JAL BIRADARI

No to bore wells
Ghagara revived
Jal bhai, Jal bahen

NEWS FROM GUJARAT

Charting future
City's pride

CLASSROOM

FUNDING AGENCY

WATER  WISDOM

NEWS FROM ABROAD

WATER IN NEWS

READERS SPACE

AN OPPORTUNITY

BOOK/DOCUMENTS

VISUAL WATCH

WEB INFO

EVENT


   
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Vol. 4   

No. 5

October-November 2002

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Urban harvesting?

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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.

12-2.jpg (8831 bytes)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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