Question

what is rain water harvesting and how it done?

Answer 1

Rainwater harvesting is the accumulation and storage of rainwater for reuse on-site, rather than allowing it to run off. Rainwater can be collected from rivers or roofs, and in many places, the water collected is redirected to a deep pit (well, shaft, or borehole), a reservoir with percolation, or collected from dew or fogwith nets or other tools. Its uses include water for gardens, livestock, irrigation, domestic use with proper treatment, indoor heating for houses, etc. The harvested water can also be used as drinking water, longer-term storage, and for other purposes such as groundwater recharge.

Answer 2

Rainwater harvesting is a technique used for collecting, storing and using rainwater for landscape irrigation and other uses. The rainwater is collected from various hard surfaces such as rooftops and/or other manmade aboveground hard surfaces.
 harvesting system has three main stages

1) Collecting & transporting rainwater

This is done through catchment areas & conduits. The catchment of a water harvesting system is the surface which receives rainfall directly.

It can be a paved area like the terrace or courtyard of a building. Conduits are the pipelines that carry rainwater from the catchment or rooftop to the harvesting system.

2) Filtration

A filter unit is a chamber filled with filtering media to remove debris and dirt from water before it enters the storage tank or recharge structure.

3) Storage in tanks for reuse / Recharging the groundwater levels