Water resources scarcity is a major topic of global discussion in recent years. The reasons for water scarcity are misallocation, misuse and degradation of water. Sustainable water management is one of the paramount importance for maintaining economic prosperity and ecological balance. Rain water is the primary source of water. Ponds, lakes, rivers and ground water are the secondary sources of water. We depend on the secondary sources of water for our requirements. But we forget the point that rain water is the source of recharge or water supply for all these secondary sources of water. We get about 100 hours of rain in a year. It is this 100 hour quantity that must be caught, stored and used over the other 8660 hours that make up a year. If not harvested, the rainwater runs off into the sea or floods low lying areas. The paper emphasizes on the method of rain water harvesting for water conservation and discusses in detail the various techniques used for rain water harvesting. Necessity