Rain Water Harvesting

Rain water harvesting system

          It is collection of rainwater from the surface which directly receives rainfall. It can be a paved area like a terrace or courtyard of a building, or an unpaved area like a lawn or open ground.A channel or gutters are required to transfer rainwater collected from rooftops to storage tanks or recharge pit.one or more down-pipes are connected to gutters to transfer rainwater from rooftops or terrace.

Storage of Direct use (Roof top rainwater harvesting)

         In this method rain water collected from the roof of the building is diverted to a storage tank. The storage tank has to be designed according to the water requirements, rainfall and catchment availability. Each drainpipe should have mesh filter at mouth and first flush device followed by filtration system before connecting to the storage tank. It is advisable that each tank should have excess water over flow system.Excess water could be diverted to recharge system. Water from storage tank can be used for secondary purposes such as washing and gardening etc. This is the most cost effective way of rainwater harvesting. The main advantage of collecting and using the rainwater during rainy season is not only to save water from conventional sources, but also to save energy incurred on transportation and distribution of water at the doorstep. This also conserve groundwater, if it is being extracted to meet the demand when rains are on.This method is less expensive and very effective and if implemented properly helps in augmenting the ground water level of the area.

Recharging ground water

        Ground water 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)  Percolation Tanks

                   ------) Multi stored buildings

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. First one or two shower should be flushed out through rain separator to avoid contamination. A schematic diagram of filtration tank recharging to bore well.