Give a short note on Rooftop rainwater harvesting.

Rooftop harvesting was common across the towns and villages of the Thar. Rainwater that falls on the sloping roofs of houses is taken through a pipe into an underground tanka (circular holes in the ground).It is built in the main house or in the courtyard. Water can be taken from a neighbour's roof through a long pipe. A hole is made through which rainwater flows down into an underground tanka.