Water harvesting is a technique of increasing the recharge of ground water by capturing and storing rainwater locally in sub­surface water reservoirs to meet the household needs. There are various reasons for water harvesting such as:

To meet the ever-increasing demand for water, reducing the run-off which chokes drains, avoid the flooding of roads. Apart from these augmenting of the ground water storage, raising water table, reducing groundwater pollution and soil erosion and supplementing domestic water requirement during summer and drought etc. are important reasons for water harvesting.

However, the water harvesting can be very beneficial where ground water levels are declining on regular basis and the availability of ground water is inadequate in lean months. This can be helpful in urban areas where due to rapid urbanization, infiltration of rain water into subsoil has decreased drastically and recharging of ground water has diminished.

There are several low cost techniques are available to recharge the ground water aquifers. Among them the water harvesting, refilling of dug wells recharging of hand pumps, construction of percolation pits, bunds and stop dams on small rivulets.

In urban areas, rainwater available from roof tops of buildings, paved and unproved areas goes waste. This water can be recharged to aquifers and can be utilized gainfully at the time of need. The rain water harvesting systems needs to be designed in a way that is does not occupy large space for collection and recharge system. The roof top rain water harvesting can be a very effective tool to fight the problem of water shortage particularly in urban areas.