Legislation on Rainwater Harvesting in Ahmedabad
In 2002, the Ahmedabad Urban Development Authority (AUDA) had made rainwater harvesting mandatory for all buildings covering an area of over 1,500 square metres. According to the rule, for a cover area of over 1,500 square metres, one percolation well is mandatory to ensure ground water recharge. For every additional 4,000 square metres cover area, another well needs to be built.
The state roads and buildings department has made rainwater harvesting mandatory for all government buildings see http://www.rainwaterharvesting.org/policy/img/gujarat.jpg
source: http://www.rainwaterharvesting.org/policy/legislation.htm