Allegiance Rainwater Harvesting System Methods of Rainwater Harvesting . How to Save Rain Water? Surface runoff harvesting. In urban area rainwater flows away as surface runoff. ... Rooftop rainwater harvesting. It is a system of catching rainwater where it falls. ... Rooftop Rainwater Harvesting System. ... Catchments. ... Transportation. ... First Flush. ... Filter. ... Sand Gravel Filter. Broadly there are two ways of harvesting rainwater Surface runoff harvesting Roof top rainwater harvesting Rainwater harvesting is the collection and storage of rainwater for reuse on-site, rather than allowing it to run off. These stored waters are used for various purposes such as gardening, irrigation etc. Various methods of rainwater harvesting are described in this section. 1. Surface runoff harvesting In urban area rainwater flows away as surface runoff. This runoff could be caught and used for recharging aquifers by adopting appropriate methods. 2. Rooftop rainwater harvesting It is a system of catching rainwater where it falls. In rooftop harvesting, the roof becomes the catchments, and the rainwater is collected from the roof of the house/building. It can either be stored in a tank or diverted to artificial recharge system. This method is less expensive and very effective and if implemented properly helps in augmenting the groundwater level of the area. Recharging groundwater aquifers Groundwater aquifers can be recharged by various kinds of structures to ensure percolation of rainwater in the ground instead of draining away from the surface. Commonly used recharging methods are:- a) Recharging of bore wells b) Recharging of dug wells. c) Recharge pits d) Recharge Trenches e) Soakaways or Recharge Shafts f) Percolation Tanks c) Recharging of bore wells Rainwater collected from rooftop of the building is diverted through drainpipes to settlement or filtration tank. After settlement filtered water is diverted to bore wells to recharge deep aquifers. Abandoned bore wells can also be used for recharge. Optimum capacity of settlement tank/filtration tank can be designed on the basis of area of catchment, intensity of rainfall and recharge rate. While recharging, entry of floating matter and silt should be restricted because it may clog the recharge structure.