2. W HAT IS WATER HARVESTING ?  It is the method by which rain water is collected for later use .
3. U SES OF RAIN WATER HARVESTING  Its used to maintain the underground water table.It is also called ground water recharge(In the picture)  Since rain water is stored for later use , it can be used at times of drought.  It reduces soil erosion as the running water is stored (to a certain extent).
4. T ECHNIQUES OF RAIN WATER HARVESTING The most basic type of rain water harvesting is the method by which the water sliding down the roof tops is collected by a gutter which goes down the pipes to be stored . Sometimes the water is let into the soil to maintain the water table. In US the rooftop rain water is collected in a sump. A subsurface dyke is built in an aquifer to obstruct the natural flow of groundwater, thereby raising the groundwater level and increasing the amount of water stored in the aquifer.
5.  In largely level terrain , the water harvesting structures are mainly crescent shaped earthen embankments or low straight concrete-and-rubble “check dams” built across seasonally flooded gullies . Monsoon rains fill ponds behind the structure .
6. WATER HARVESTING IN DIFFERENT PARTS OF THE WORLD In China and Brazil rooftop rain water harvesting is practiced for providing drinking water , water for irrigation , for livestock and to maintain the water table. In Bermuda and US all new buildings includes water harvesting sufficient for the residents. In UK rain water (water butts) tanks are used for rain water harvesting In Australia rainwater harvesting is typically used to supplement the reticulated mains supply. In south east Queensland, households that harvested rainwater doubled each year from 2005 to 2008, reaching 40% penetration at that time (White, 2009 (PhD)).
7.  In Senegal and Guinea-Bissau, the houses of people are frequently equipped with homebrew rainwater harvesters made from local, organic materials. In the Irrawaddy Delta of Myanmar, the groundwater is saline and communities rely on mud-lined rainwater ponds to meet their drinking water needs throughout the dry season. Some of these ponds are centuries old and are treated with great reverence and respect. In India : (i) Khandins and Nadis in Rajastan (ii)Bandhara and Tals in Maharashtra (iii)Bhundin in MadhyaPradesh and UttarPradesh
8. (iv) Ahars and Pynes in Bihar(v) Eris (tanks) in Tamil Nadu(vi) Surangams in Kerala(vii)Khattas in Karnataka