13-10-2014, 12:37 PM
Abstracts: All sources of water are ultimately rain. Therefore, all water supply systems are, in effect, rainwater-harvestingsystems. A proper definition for this term to understand its spirit would, in effect, necessarily have to take into consideration the difference in catchments. While previously catchments were typically far off from the urban area they served, now the city itself is seen as a catchment for its water requirement. Rooftops, paved areas and unpaved areas and the entire city itself is, therefore, to be managed as a water provision area. As the Centre for Science and Environment, Delhi (India) puts it ‘CATCH WATER WHERE IT FALLS’ would be a good definition of rainwater harvesting. The process of rainwater harvesting would encompass catching rainwater, directing it to an appropriate location, filtering it if required and storing it for use. Storage could be in tanks, sumps, ponds or lakes wherever appropriate and conditions permitting recharge of ground water would also qualify as storage. Harvested water could be used immediately as a first choice thus saving city level supplies or ground water for a future date or a decision could be taken to store it for later use, say during water shortage days. Domestic rainwater harvesting or rooftoprainwater harvesting is the technique through which rainwater is captured from roof catchments and stored in tanks/reservoirs/ground water aquifers. It also consists of conservation of roof top rainwater in urban areas and utilizing it to augment ground water storage by artificial recharge. It requires connecting the outlet pipe from rooftop to divert collected water to existing well/tube well/bore well or a specially designed well. Rooftop harvested rainwater is more safe for drinking purposes than the runoff harvested water. Rooftop harvesting needs to have safe storage facilities to keep the water fit for drinking. First flush of rainwater is discarded. A number of alternative technologies are available for rooftop harvesting and storage to suit the varying situations and the budgets.