(i) Nearly every home in Rajasthan's semi-arid and desert regions—especially in
Bikaner, Phalodi, and Barmer—has historically included an underground tank, or tanka, to hold drinking water. One family in Phalodi had a tank that measured 6.1 metres deep, 4.27 metres long, and 2.44 metres wide—the size of a huge room. The tankas were constructed inside the main house or the courtyard and were a part of the sophisticated rooftop rainwater gathering system. They had a hose connecting them to the dwellings' sloping roofs.
Rain that fell on the rooftops would pass through the pipe and accumulate in these "tanks" below ground. Usually, the initial round of rain was not collected since the pipes and roofing would be cleaned. After that, rainwater from the next showers was gathered. When all other supplies of drinking water run dry, especially during the summer, the rainwater may be kept in the tankas until the next downpour. This makes it an incredibly dependable source of water. Rainwater, or "palar pani" as it is known locally, is regarded as the purest type of natural water.
(ii) A practical substitute in terms of the environment and socioeconomics is a water harvesting system. In addition to highly developed hydraulic systems, ancient India had a remarkable water-harvesting system legacy. By the local ecological conditions and their water demands, people created a wide range of strategies to extract rainwater, groundwater, river water, and floodwater. They also had an extensive understanding of rainfall regimes and soil types. For agricultural purposes, people in hilly and mountainous areas constructed diversion channels similar to the Western Himalayan "guls" or "kuls."
In Rajasthan in particular, "Rooftop rainwater harvesting" was a popular method of storing drinking water.
To irrigate their fields, inhabitants in Bengal's flood plains created inundation channels. Agricultural fields were transformed into rain-fed storage structures, known as "khadins'' in Jaisalmer and "Johads'' in other areas of Rajasthan, in arid and semi-arid regions so that the water could stand and hydrate the soil. To meet their water demands, the people of Gendathur, a remote, underdeveloped village near Mysore, Karnataka, have erected rainwater harvesting systems on the roofs of their homes. With the installation of this system in close to 200 homes, the community has gained the unique distinction of having
an abundance of rainwater. In Shillong, Meghalaya, rooftop rainwater collecting is the most popular method. The 55-kilometer distance between Cherrapunji and Mawsynram makes it intriguing.
The world's highest rainfall originates from Shillong. However, Shillong, the state
capital, is severely short on water. In the city, almost every home has a rooftop rainwater collection system. Rooftop water harvesting provides the household with roughly 15– 25% of its overall water needs. The state of Tamil Nadu is the first in India to mandate rooftop rainwater harvesting systems for every home in the region.