Rainwater harvesting is not a new science in India. There are several traditional practices across the country where rainwater was stored safely and used in times of need. One such example is the 'Taankaa' system in Gujarat.
Around 10,000 houses in the city of Ahmedabad have large underground tanks or 'taankaas' that can each store 25,000 litres of rainwater. These serve as mini reservoirs for families during water scarcity. When tested for quality, they have proven to meet WHO norms.
This book by Shree Padre talks more about these taankaas and the principle that they are built on.