Legislation on Rainwater Harvesting in Bangalore
In order to conserve water and ensure ground water recharge, the Karnataka government in February 2009 announced that buildings, constructed in the city will have to compulsorily adopt rain water harvesting facility. Residential sites, which exceed an area of 2400 sq ft (40 x 60 ft), shall create rain harvesting facility according to the new law.
source: http://www.rainwaterharvesting.org/policy/legislation.htm