Sunday, 6 July 2014

Rain dance on the rooftop

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.
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.

Kalyani being restored by volunteers

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 

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.

Cement ring well in a residence of Bangalore created for ground water recharge from roof top rainwater 
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!