Wednesday, April 15, 2009

Rainwater harvesting: A case study

rainwater harvesting

Considering Hiranandani Gardens', Powai, location in an area that's largely rocky and paved, rainwater harvesting (RWH) wasn't an easy endeavour. But, since its inception in April-May 2003, RWH has proved to be quite beneficial!

Rainwater, falling on the uppermost part of the hill, is directed and collected in the artificial ponds or dams. The water, coming down as nallah from the hill is taken through hume pipes to the wells. Incidentally, these wells are not lined or cemented beneath. Besides acting as collection chambers, they also increase the water's travelling time.

And then, the water is collected in a semicircular pond - not lined beneath - which gives further time for the water to percolate. Further down, before the water enters Powai Lake, a 10m deep well, 10m in diameter has been constructed.
That apart, various percolation pits dug-cum-bore (DCB) wells are constructed in the area around the bore-wells - there're 12 DCB and 13 percolation pits in Hiranandani Gardens. Water from nearby storm water drains is directed to these structures and then, the water is percolated down to earth.

Besides, filters of sewage treatment plants are used for cleaning or filtering this water. The water thus pumped is in the tune of 10 million litres per day. This water is used for construction, carwash and flushing applications. The residents can easily expect around two lakh litres of water every day, even during the scorching summers.

Roof water harvesting has also been incorporated in various commercial buildings such as Olympia, Alpha, Sigma, Sentinel, Spectra and Prudential Daily. Flush-water and cooling tower requirement to the tune of two to three lakh litre of water per day in these buildings is met through roof water harvesting and subsurface collection and pumping.

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