Ancient Rainwater Harvesting Techniques, India

In ancient India – as in many parts of the ancient world today – rainwater was traditionally collected and stored for domestic use. An example is the 10th century AD Chandragiri Fort in the south Indian state of Andhra Pradesh.

Chandragiri Fort has two water harvesting systems. One was used for creating water self-sufficiency for its residents – especially important when access to outside sources was impossible such as during wars. The other structure provided water to the fort's moat.

Although both the fort and the moat are in a dilapidated condition today, the harvesting system is still up and, literally, running. A steep hill of fresh granite rests within the 74-ha (183-acre) area of the hilly land around the fort. "Fresh" rocks have not been weathered – suffered physical disintegration or chemical decomposition – and are ideal as they allow water to roll down with minimum loss of moisture. This granite hill allows almost all the rainwater to collect in a 10,000-cubic metre (2.6-million gallon) capacity open reservoir carved in impervious granite at the foot of the hill by a 10th century architect.

This structure is manmade and a great deal of scientific wisdom evidently went into its construction. Trees surround it to minimize evaporation, and the lotus plants in the reservoir appear to have a purifying effect on the water.

The whole system is still in such good condition – the catchment is properly protected and the container is clean – and the water so pure, that this raw, untreated water is perfect for human consumption. The geology department of Sri Venakteshwara University (the author of this case study was part of the research team) tested the water and found it excellent for drinking.

The team also found that there is scope to enlarge the size of the reservoir to 500,000 cu m (132 million gallons), thus making potable water available to a good portion of Chandragiri village.

The Chandragiri Fort example is particularly ingenious because the its architects realized that catching water from steep hillslopes would ensure purity for centuries because the extreme slope of the land would not allow habitation to grow around it, unlike on the plains. On the other hand, if a reservoir had been constructed across a river, it would have silted up within a few decades.

R. Jagadiswara Rao got his Ph.D. in geology in 1965. His work as a teacher, researcher, field worker, consultant and extension worker in the management of land and water resources dates back to 1965. He retired as Principal and Professor of Geology at Sri Venkateswara University, Tirupati, India. He has been part of water organizations and water forums over the years and in December 2002, he received a special award as a Water Messenger by the sponsors of the 3rd World Water Forum. Professor Rao's ambition is to work toward a solution to water problem in cooperation with the giants in the field through pragmatic, innovative and cost-effective methods.