Rain
dance on the rooftop
Bangalore is a
unique city because it has neither river nor sea close by. Our erstwhile rulers
had planned lakes and water bodies to collect rain water. It was the most
systematic, common-sense community approach to address the water needs of the
population.
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Traditional Open well |
The water thus collected was used through ‘kalyanis’ or step wells
and open wells. Open wells were recharged by tanks, water bodies and surface
water flow.
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Kalyani being restored by volunteers |
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Kalyani in the premises of a temple |
But as urbanization happened, this approach could not be sustained. Water
sources got polluted and dried up. Encroachment and diversion of natural
drainage of rain water soon turned most of these tanks into garbage dumps!
Ulsoor Lake
We began to look
at far off places like Hesarghatta and Thippagondanahalli for water supply. As
demand continued to mount, we went up to 95 km to River Cauvery to meet our
water needs. And now we are in the unique situation of pumping water (most our
requirement) from a distance of 95 km against a gradient of 500
meters!
Urbanization and increase in population are exerting tremendous pressure on
conventional water supply. The time has come to look for new sources or at
recycling water. Recycling is not a phenomenon that is well-accepted in India due to
social reasons. We just cannot imagine recycling our bath water!
Ulsoor Lake
Why fret when there’s an easy solution on hand: Rainwater. It is available in
abundance in a place like Bangalore which receives 1000 millimeters of rain
water (or 40 inches of rainfall) annually. This translates to 2, 30, 000 liter
of pure water in a plot of 2400 sq ft — a plot where an individual can
comfortably build a house / apartment. When we have such a boon, why don’t we
use it? If we do, at least 50 per cent of our water requirement can be met with
this intervention. And the pressure on a service provider like the Bangalore
Water Supply and Sewerage Board (BWSSB) will
dramatically come down. The BWSSB currently supplies water to around 7,00,000 properties
only (against over 18,00,000 properties of Bangalore). If everyone practices
rain water harvesting in Bangalore,
an equal number of new connections can be facilitated and in the next 25 years,
Bangalore can
still sustain with its available water sources.
So what exactly is rain water
harvesting?
It is a very simple intervention to
collect rainwater. The first and easiest approach is rooftop rainwater
harvesting. Collect the roof water which is already flowing through a down
water pipe, attach a filter at the end of the pipe to separate the dirt, dust,
bird dropping and leaves and divert the filtered rainwater into a storage
unit such as a tank / sump. This can give you sustained water supply
during the rainy season.
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Cement ring well in a residence of Bangalore
created for ground water recharge from roof top rainwater
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The excess water which overflows from
the sump or tank can be used to recharge the groundwater through a pre-cast
cement ring open well. When the rainwater is discharged into this well, it
slowly percolates into the groundwater table and can be withdrawn through a
borewell or an open well. These two systems can provide sustained water supply
throughout the year. Rainwater
can also be collected in playgrounds, parks and roads for large-scale
groundwater recharge. Harking
back to the time when I was in school, I remember fetching water twice a day
from an open well outside my village, Ammanaghatta in Gubbi taluk in Tumkur
district. I did this religiously all through my childhood! I saw piped water
only when I moved to Bangalore.
But soon the bore well in our house in Vijaynagar dried up and I had to fight
for water for the first time in my life! At that time, I was working on
sustainability projects. So I started planning a house which would use Nature’s
gifts for its needs. The outcome is ‘Sourabha’. I will take you on a tour of
‘Sourabha’, in my future posts!
Excellent suggestions; I now have ideas for my present.
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