Rain water harvesting is the collection or storage of water using scientific techniques at places where there is rainfall. The rain water thus collected can be used for domestic or agricultural purposes. The practice of rain water harvesting has been prevalent from ancient times. It is the best way to conserve water and make the society realize the importance of water. These methods are simple and cost effective also. They are now being implemented not only in areas with scarcity of water but also in places with abundant rain. The water that is wasted during rains can be put to proper use after cleaning. This is the most effective way to conserve water. The water can be stored in tanks instead of allowing them to flow into drains. Storage of water and water recharging through technical processes comprise rain water harvesting.

Catchment is the area from which the rain water is collected. Conveyance system includes rain gutters and down pipes which channel the rain water from catchment to the storage tanks. Storage system is the most important part of rain water harvesting systems. A simple system can be constructed for areas which receive frequent rainfall, while it needs to be carefully designed in areas where there is scanty rainfall. Structures mainly used to collect rainfall are rain barrels, underground or open slumps.

builders in Kochi are now stressing on the need to install rain water harvesting system. Not only in Kerala but in all other parts of India rain water harvesting is now being widely used.