Rain Water Harvesting or(RWH) is the collection and storage of rain, rather than allowing it to run off. Rainwater is collected from a roof-like surface and redirected to a tank, cistern, deep pit (well, shaft, or borehole), aquifer, or a reservoir with percolation. Dew and fog can also be collected with nets or other tools. Rainwater harvesting differs from stormwater harvesting as the runoff is collected from roofs, rather than creeks, drains, roads, or any other land surfaces. 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, and residential and household-scale projects, usually financed by the user. However, larger systems for schools, hospitals, and other facilities can run up costs only able to be financed by owners, organizations, and governmental units. Tamil Nadu was the first state to make rainwater harvesting compulsory for every building to avoid groundwater depletion. The project was launched in 2001 and has been implemented in all rural areas of Tamil Nadu. Posters all over Tamil Nadu including rural areas create awareness about harvesting rainwater. TN Govt site. It gave excellent results within five years, and slowly every state took it as a role model. Since its implementation, Chennai had a 50% rise in water level in five years and the water quality significantly improved.
Rainwater is very good for plants as it contains a lot of nutrients. It is slightly acidic, naturally, which helps in maintaining pH balance. It is believed that rain contains vitamin B12. It is true but rain does not inherently contain Vitamin B12.Composition of Rainwater
The constituents of rainwater are built primarily by dissolved particulate materials from the upper troposphere and secondarily by dissolved gases. Rainwater compositions vary largely as per the geography of the place; the rain near coastal regions have salt content and CO2 as Bicarbonate anion (acidic pH). Even though rain absorbs gases and pollutants from the atmosphere, it gets pure as it reaches the earth’s surface.