Rain Water Harvesting is a way to capture the rain water when it rains, store that water above ground or charge the underground and use it later. This happens naturally in open rural areas. But in congested, over-paved metropolitan cities, we need to create methods to capture the rain water.
There are many types of systems to harvest rainwater. Notable systems are systems for runoff rainwater (eg hillside run-off) and rooftop rainwater harvesting systems. The type used depends greatly on the purpose (domestic or industrial use) and to some extent also on economics and physical and human considerations.
- Currently in China and Brazil, rooftop rainwater harvesting is being practiced for providing drinking water, domestic water, water for livestock, water for small irrigation and a way to replenish ground water levels. Gansu province in China and semi-arid north east Brazil have the largest rooftop rainwater harvesting projects ongoing.
- In Bermuda, the law requires all new construction to include rainwater harvesting adequate for the residents.
- The U.S. Virgin Islands have a similar law.
- In Indus Valley Civilization, Elephanta Caves and Kanheri Caves in Mumbai rainwater harvesting alone has been used to supply in their water requirements.
- In Senegal/Guinea-Bissau, the houses of the Diola-people are frequently equipped with homebrew rainwater harvesters made from local, organic material.
- In the United Kingdom water butts are oft-found in domestic gardens to collect rainwater which is then used to water the garden.
- In Colorado, water rights laws severely restrict rainwater harvesting -- a property owner who captures rainwater is effectively stealing it from those who have rights to take water from the watershed.
References: www.akash-ganga.com ,www.viksat.org,www.en.wikipedia.org/wiki/Rainwater_harvesting