Answer the following questions in about 120 words.

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

People in Rajasthan follow rooftop water harvesting to store drinking water. In the arid and semi-arid regions, the agricultural fields are covered in water storage structures which store the rainwater. This allows the soil to be moistened, like we see "khadins" in Jaisalmer and "Johads" in the other parts of Rajasthan. In the semi-arid and arid regions, particularly in Bikaner, Phalodi and Barmer, most of the houses have traditional underground water storage tanks or "tankas" for the storage of drinking water. The size of the tanks differ, they can a big room inside the main house or a storage tank in the courtyard. They are connected to the sloping roofs of the houses through a pipe. The rainwater falls down the pipes and is collected in the underground "tankas". In the western part of the state, the rainwater harvesting has declined due to the construction of the Indira Gandhi Canal. This makes the availability of water in plenty and thus, people refrain from using the rooftop rainwater harvesting technique.