Discuss how rainwater harvesting in semi-arid regions of Rajasthan is carried out.

In arid and semi-arid regions, agricultural fields are converted into rain fed storage structures that allow the water to stand and moisten the soil like the 'Khadins' in Jaisalmer and 'Johads' in other parts of Rajasthan. In areas of Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water. These tankas were part of the well-developed rooftop rainwater harvesting system and were built inside the main house or the courtyard. They were connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops is collected and stored in the tankas.