How to implement rainwater harvesting in unauthorised houses?

With 92 per cent of buildings in the national capital lacking a completion certificate, making these unauthorised, the Delhi High Court has asked the civic authorities how will they implement rainwater harvesting in such structures as the rules apply only to authorised houses.
"Are you aware that 92 per cent of Delhi does not have a completion certificate and 80 per cent does not have a sanctioned plan. When building itself is unauthorised, how would you implement rainwater harvesting? Rules of rainwater harvesting apply to only authorised buildings," a bench of justices B D Ahmed and Jayant Nath asked the authorities.

The observations were made during hearing of a PIL filed by advocate R K Kapoor seeking implementation of rainwater harvesting systems in all buildings in the national capital.
The court asked the petitioner to come up with some ideas for making rainwater harvesting rules applicable to unauthorised structures also and listed the matter for hearing on January 25 next year.
On an earlier date of hearing, the Delhi Jal Board had told the court that it has launched three rainwater harvesting information centres that will recommend the type of conservation practices to be adopted and also train plumbers and masons in designing such facilities.