Even as the monsoon stands clear of the city and a rather lacklustre performance by the rain gods is predicted this year, Bangaloreans are prepping to make the most of it.

Driven by the depleting ground water resources and a burgeoning population, enforcing rainwater harvesting could just be the antidote to taps running dry. A threat to cut the existing supply of Cauvery water is the incentive to get Bangaloreans moving.

While it cannot replace the water supply system, rainwater makes for a necessary supplementary source. Bangalore currently receives 910 MLD (million litres per day) of water and falls short by 390 MLD of water required.

Bangalore Water Supply and Sewerage Board (BWSSB) imposed mandatory rainwater harvesting (RWH) in the city three years ago. The Act passed in 2009 makes it compulsory for rainwater harvesting structures to be set up in all buildings occupying an area of 2400 sq ft and all proposed constructions on a land area of 1200 sq ft and over. Kemparamaiah, Chief Engineer at BWSSB said that so far 41326 buildings covering a land area of 1200 sq ft and 2400 sq ft have incorporated RWH.

Photo credit: Hari Krishnan
Rainwater harvesting involves collecting and storing rainwater while in the groundwater recharge method, the water is directed to recharge pits and wells to replenish underground water.

A contractor Sridhar says most of the residents he has dealt with opted for recharge pits as the storage model requires maintenance. Rainwater is channeled through down water pipes to a filter and then stored in a storage tank. Stored rainwater can be used for a variety of chores ranging from gardening to washing cars and utensils. While rainwater is pure it can get contaminated due to particles on the roof which makes a sound filtration system necessary if you want to utilise it for drinking, cooking or bathing.

Jameel, who has installed both storage and recharge pits is of the opinion that stored water may or may not be utilised whereas a recharge pit will ensure that the underground water is replenished.

Subramanian says that they got a recharge pit in their apartment complex which has a terrace area of about 10000 sq ft more than six years ago and they have never faced a dearth of water, and have a continuous supply of water from their borewell. 

Photo: bwssb.org
Nanda Kumar has set up a variety of RWH structures from recharge pits to sumps with pop-up filter and tank storage. He has seen a good demand from both companies like IBC Knowledge Park and residential buildings. He has installed it for over 150 buildings so far including a 22 ft deep well with a filter and pit for a company.

A resident of Vignanapura, where only one out of every 20 borewells dug actually has water, had a well of around 15 feet dug up last year and after heavy rain it is usually full and is sucked up by the earth within minutes but water continues to be an issue in the neighbourhood.

The yield is determined by the roof area. According to BWSSB, Bangalore’s annual average rainfall of about 1000 mm can easily help a 2400 sq ft house collect and use around 2.23 lakh litres of water.

A coffee planter, Thimmiah feels RWH is not practical considering the rainfall that Bangalore receives. The amount of water that can be collected from their office roof is negligible, the stored water would last a day or ten days. The outskirts and large open spaces which are not concretised would naturally be recharged and are ideal for harvesting rain. 

A first of its kind in India, BWSSB’s Sir M Visvesvaraya Rain Water Harvesting Theme Park in Jayanagar, gives free information about RWH to the public and has 26 types of RWH models.

By Anuradha Prasad/ Raintree Media Features/ www.raintreemedia.com