According to the Andhra Pradesh Water Land and Trees Act, 2002 when groundwater level is below 20 metres, digging of borewells is banned.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/andhra-pradesh-records-deepest-groundwater-level-country
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/deccan-chronicle-hyderabad
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/andhra-pradesh
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/groundwater-recharge
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/farmers
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-management
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-resources