Save rainwater: How to save rain water next monsoon?

The monsoon in Mumbai has arrived and the amount of rainwater that could have been harvested by the thousands of buildings in the city has once again seeped down the drain. However, there's still hope. Rainwater harvesting is not too difficult to manage what with the civic authorities too pooling in their bit to convince the citizenry of its benefits and subsequent load-shedding effect on the city's water resources.

Consider this: Mumbai needs about 3,400 million litres of water daily (MLD). But the Mumbai Municipal Corporation can provide only 2,900 MLD.

Incidentally, the city receives approximately 2,000 mm of rainfall during June to September period. It translates into a whopping 8, 63,480 million litres of water that can provide up to 2,365 MLD for use in the city. Even if three fourths of the city can save rainwater, it could surely provide the much-needed breather to the BMC.

In some of the recent developments, the BMC has made rainwater-harvesting (RWH) procedures mandatory for new developments and constructions larger than 1,000 sq m and undertaken after October 2002 failing which builders would not get No-Objection Certificates (NOCs) to transfer rights.

And since, it would be inconvenient to enforce RWH by force of law, in the case of existing buildings the BMC has decided to offer financial assistance of over Rs two lakh - even freebees by way of FSI, assessment subsidies and technological support to the initiated.

But then, most Mumbaikars seem to be reluctant to implement rainwater harvesting in their housing societies. "The problem is that residents are so used to getting their daily water that they feel spending money for rainwater harvesting is an avoidable waste little realising that it will be the need of the hour in a few years," says Goregaon-based Vasant Trivedi, whose housing co-operative society implemented RWH during the last monsoons.

"While for drinking we use BMC water, the harvested water is used for non-potable purposes such as gardening, washing, sanitary uses etc.," offers Mr Trivedi. Statistics show that non-potable purposes take up more than 10 per cent of the water supplied by the BMC.

Following a one-time investment, RWH processes turn out to be a lot more cost-effective than the tanker water which is used regularly by most residents of the western suburbs plagued with water shortage issues. Tanker water comes at a minimum of Rs 40 per thousand litres sometimes even a lot more.