Rainwater harvesting is the process of catching, filtering, and collecting water to conserve it for later use. The water is collected from rooftops, where it flows down to the gutters, through downspouts, and into a collection tank. These storage tanks take on many sizes, and they can be installed above ground or beneath your yard. They can be connected to hoses that you can use on your lawn, filtration systems that pipe into your house, or other systems where the water can be used as needed.
Dew and fog can also be collected with nets or other tools. Rainwater harvesting differs from stormwater harvesting as the runoff is typically collected from roofs and other surfaces for storage and subsequent reuse. Its uses include watering gardens, livestock, irrigation, domestic use with proper treatment, and domestic heating. The harvested water can also be committed to longer-term storage or groundwater recharge.
Rainwater harvesting is one of the simplest and oldest methods of self-supply of water for households, having been used in South Asia and other countries for many thousands of years. Installations can be designed for different scales including households, neighbourhoods and communities and can also be designed to serve institutions such as schools, hospitals and other public facilities