Water scarcity is a serious problem throughout the world for both urban and rural communities. More and more water is required for domestic, construction and industrial use. The rate of withdrawal is far in excess of the rate of recharging the water table. In India, water is considered divine and referred to as thirtha. But, there is nothing holy in our treatment of our water sources. Pollution and overexploitation have shrunk the availability of clean and potable water to a trickle.

Urbanization has resulted in overexploitation of ground water, reduction in open soil surface and water infiltration rate and a resultant deterioration in water quality. Apartments and industrial units face acute water shortage forcing them to spend considerable amounts of money to purchase water from municipal and private water suppliers. The rural scenario is equally grim. The population explosion necessitates a proportionate increase in food production, which in turn demands more land, more fertilizers and pesticides and more water.

The water policy of the Government of India puts a norm of 180 litres per capita for our domestic needs. But it is not possible to supply even 100 litres per day even in urban areas. 30 million Indians spread out over an area of 7 lakh sq. km., mostly in the west and North West regions; face an acute scarcity of potable water especially in the summer months.

The main source is precipitation, in the form of rain or snow. The annual rainfall in India is 400 million hectare meter. This rainwater can be used to recharge the ground water, by adopting a simple technique called rainwater harvesting. Rainwater harvesting means making use of each and every drop of rainwater to recharge the groundwater, by directing the rainfall to go into the well or under the ground, without wasting the rainwater.

India uses only 10-20 percent of its annual rainfall. When it rains, only a fraction of the water percolates and reaches the ground water aquifers, while the major part of the rainfall drains out as run-off and goes unused into the ocean. Further, lack of adequate storage facilities necessitate water being let into the sea to prevent breaching and flooding. The increasing numbers and depth of bore wells and wells and their unrestricted use threaten India's ground water resources.

Advantages of using rainwater

1. Rainwater harvesting promotes self-sufficiency and fosters an appreciation for water as a resource. It also promotes water conservation.
2. Rainwater harvesting also conserves energy as the energy input needed to operate a centralized water system is bypassed. Many systems require only a small pump to create water pressure in household pipes.
3. Local erosion and flooding from impervious cover associated with buildings is lessened as a portion of local rainfall is diverted into collection tanks.
4. Rainwater is one of the purest sources of water available. Its quality almost always exceeds that of ground or surface water.
5. It does not come into contact with soil or rocks where it can dissolve minerals and salts nor does it come into contact with many of the pollutants that are often discharged into local surface waters or contaminate ground water supplies
6. Rainwater is soft. It can significantly lower the quantity of detergents and soaps needed for cleaning. Soap scum and hardness deposits do not occur.