Rainwater harvesting (RWH) is the practice of collecting and storing rainwater for later use. It's a sustainable way to conserve water and manage stormwater runoff. RWH can be done in a variety of ways, including: 

Roof-based:

Collecting rainwater from a roof and channeling it into a storage vessel 

Land-based:

Collecting rainwater from other 
impervious surfaces, such as sloping or plain ground 

Groundwater recharge:

Constructing structures to recharge the groundwater with rainwater.
RWH has many benefits, including: 

Reduced water bills:

RWH systems can be cost-effective and reduce your reliance on municipal water supplies 

Ecological benefits:

Storing water underground is environmentally friendly 

Reduced flooding:

RWH can help reduce flooding and erosion by reducing the flow of stormwater 

Groundwater recharge:

RWH can help recharge the groundwater table 
RWH systems can be designed for different scales, from households to communities and public facilities.