Rainwater harvesting (RWH) ensures a minimum of 120 days’ of water supply for four persons in a household annually, according to water expert S. Vishwanath.
“An average annual rainfall — on a 100 sq. m roof area — would in theory generate 80,000 litres of water, out of which about 77,600 litres could be harvested efficiently.
Experts in the city feel that although the concept of rainwater harvesting is becoming popular, policymakers, architects, engineers and the public need to be made more aware of the methods. “Since RWH is related to the soil profile and hydrogeology, specific methods have to be developed for specific sites,” he said. Demonstrations of such simple techniques as recharge pits in minor drains that are not polluted with wastewater, and recharge of open wells and borewells from rooftops should be encouraged as Bengaluru itself has more than one lakh wells.
Tips for a simple RWH system at individual houses and apartment complexes:
* Have a sump to store rainwater, apart from maintaining a clean catchment area or the rooftop to avoid bacterial growth. Install a pipeline to channel the water from the rooftop to the sump after consulting RWH experts and a plumber
* You don’t have to build a new sump, the existing one will do
* If you has a borewell, whether functioning or not, connect the rooftop with pipes and filter to the borewell. This is for recharging
* If you have an existing well, connect the pipes and filter to the well
* Place an HDPE plastic tank and collect the rainwater directly, this system is called a rain barrel
* Make a recharge well of 3-ft diameter and 10-ft depth. Do not fill it with anything. Direct the roof water into the recharge well.
* On an average, it would cost Rs. 10,000 to Rs. 20,000 for one household (excluding the sump)
In layouts, one has to additionally follow two more points:
* Connect storm-water drains to recharge wells placed at regular intervals
* Layouts at the lowest points can make a small percolation pond for storm water
(Call 91-80-41672790 or email:rainwaterclub@gmail.com for more details)
Everyone should mandatorily visit the RWH Theme Park created on a 1.5-acre space by the BBMP at Jayanagar 5th Block and choose from the demonstrated examples. — S. Vishwanath, water expert
