There are a number of notifications and orders on rainwater harvesting but few of them have been implemented.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/rainwater-harvesting-orders-stay-paper
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-harvesting
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-groundwater-authority-cgwa
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/tubewells
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/central-groundwater-board-cgwb
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi-jal-board-djb
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-supply
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-resources