RAIN WATER HARVESTING, TYPES OF THE RAIN WATER HARVESTING AND ITS USES:-

Simply put , rainwater harvesting is the process of collecting and storing the rain water that runs off from roof tops,parks ,roads ,open grounds and other such spaces for later uses .This water is either used directly for household or the agricultural purposes or is used to recharge the ground water .Rain water harvesting can broadly be divided into three categories based on the type of its uses ,the area in which harvesting is carried out and the people involved.(2) Storage of recharge:- Based on the type of usage ,structures can either be used to store the collected water for use or to recharge nearby ground water resources. (2) Urban or rural :-- Rural harvesting is mostly done through traditional practices like zing and is carried out in surface storage bodies like rivers and lakes,urban harvesting,due to lack of open space for capturing the runoff,is mostly done in sib-soil storage structures like recharge pits and wells  (3) Rooftop or drive way harvesting:-The terrace related to the roof slab greatly restricts the scope for the rain water harvesting,rain water as a considerable amount of water that falls around the build -up area is left out of the building as run off .This run off water should not be led into a pump for immediate use or to a source well ,but it can be very well be directed into recharge wells to aid in groundwater replenishing. (4) How to harvest:--Rain water harvesting systems can be set up any where, individual homes ,schools , apartments and slums --all it require some understanding of which set up will work best for an area  . Storage for direct use:-- Rainwater is collected from the catchment -roof -of a building which is connected to a storage tank. This storage tank is designed according to the water requirements of the building and amount of the rainfall received .When it rains ,the water collected on the roof is diverted into this tank and can be used for any purpose.It acts as an alternative source to ground water . Recharging ground water:-- Rain water is collected in any open space connected to a recharging pit ,bore well ,dug well or a trench .This pit contains layers or filters made out of gravel or the brick pieces .When it rains,water from the open space enters the recharge pit or well where it is filtered and released into ground water to aid in its recharge. USERS:-- Agriculture:-- The example of five Caribbean countries has shown that rainwater harvesting can significantly reduce the risk of losing annual harvest due to soil or water scarcity and reduce the risks associated with flooding and the soil erosion during high rainfall . DOMESTIC:--China's Gansu province and semiarid areas of Brazil have the largest roof top rainwater harvesting project in the world. About forty percent of the Thailand's current rural population utilities rain water harvesting and is one of the largest example of self supply of water world wide. According to official stastics 22.94 lakh buildings out of 23.92 lakh buildings in the Tamilnadu have the harvesting facilities.INDUSTRY :-- Frankfurt airport, Germany helps save approximately one million cubic metres of water annually.Water is collected on roofs of the new terminal,connected to the six tanks in the airport basement and mainly used for the toilets , watering plants and cleaning air conditioning system.