Understand construction

Understanding Rain Water Harvesting

Jan 05 2020

Malak Mehta

Rainwater harvesting is storage of rainwater for reuse such that it does not get run off and wasted. Rainwater can be collected from roofs and catchment area and then diverted to the storage area where it can be efficiently stored for reuse. The harvested water can be used for drinking water, house hold purposes, longer-term storage for future use, and for other purposes such as groundwater recharge.

A rainwater harvesting system follows the below process -

Collection through catchments

The rainwater collection done through catchment areas which are nothing but surfaces over which rain falls directly. It can be terrace, garden or paved open space or even a courtyard. Sloping roof, RCC slabs, weather-sheds, corrugated sheets, fabricated roofs, all act as catchment areas.


At the edges of sloping roofs or fabricated roof structures, channels are installed such that the rainwater flows from these roofs to the channels and from these channels to drain pipes. These channels are known as gutters.

Transportation through conduits

Transportation of rainwater means proper flow of rainwater from collection area to the storage area. This is done with the help of pipelines or conduits. These conduits are made of Galvanized Iron (GI) or PVC. Gutters collects the rainwater from the sloping sheds and roofs. These gutters are connected further to pipelines which further carry rainwater from the catchment to the harvesting system finally into the storage. Terraces and paved grounds have a direct flow of waters into the pipelines.

Filtration tank

Rainwater is filtered to remove unwanted dirt and micro-organism before it enters the storage tank or recharge structure. Various types of filters are available - Charcoal water filter, Sand filters, Horizontal roughing filter and slow sand filter.

Storage tanks

The rainwater once filtered is ready for direct usage. The filtered water is thus stored in tanks or barrels. The tanks can be designed with RCC or masonry depending on the volume of water to be stored. These tanks need to carefully placed, either underground or partly underground.

Recharge of groundwater levels

The collected rainwater can also be used to recharge the groundwater levels. Ground recharge is can be done at a shallow level using recharge trenches and permeable pavements. While bore wells and recharge pits are dig deep underground where water can be stored and recharged.

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