In the semi-arid regions of Rajasthan, rainwater harvesting is a traditional and sophisticated practice. The most common method involves building underground tanks or 'tankas' for storing drinking water. These are large, circular pits connected to a sloping rooftop catchment area via pipes. The first spell of rain is often allowed to wash away, cleaning the roof and pipes. Subsequent rainwater is collected and stored in the 'tanka', which keeps the water cool and makes it a reliable source of drinking water until the next rainy season. In some areas like Jaisalmer, 'Khadins' are used for agriculture. These are long earthen embankments built across gentle slopes to harvest rainwater, which then saturates the soil for growing crops.