In which parts of Rajasthan, Tankas are built for water preservation?

Tankas are built for water preservation in the Western parts of Rajasthan. The tankas are the traditional technique of rainwater harvesting. These tankas are 4 to 5 metres deep cylindrical tank-like structures. These are constructed out of stone whose upper part is usually covered. Most of the tankas in Rajasthan are constructed under Jal Swavlamban scheme.