Rainwater Harvesting – Methods, Advantages & Disadvantages


Rainfall is a naturally occurring source of water. Every year, some parts of the world experience water shortage or drought conditions. So rainwater harvesting is done to overcome the difficulties during the situations like water crisis and drought.

Rainwater harvesting has been practiced since ancient times. In most developing countries, the system of rainwater harvesting is adopted due to the variation in the amount of rainfall every year. Rainwater harvesting helps in collecting and storing water as well as in recharging the groundwater.

What Is Rainwater Harvesting?

Rainwater harvesting is the process of accumulating and storage of rainwater in a systematic manner, rather than allowing the rainwater to runoff. It is a technique by which the rainwater can be harvested from roofs and other such surfaces to be stored for future use. The rainwater is stored in a rainwater tank. Rainwater harvesting helps to fulfill the need for water during drought or water crises.

The rainwater can be accumulated in a water tank or it is also used to recharge the groundwater by using specific methods and techniques. The stored water can be used for domestic, commercial, and agricultural purposes like cleaning, washing clothes, irrigation of land, in toilets and bathrooms, and even for drinking purposes after some purification treatment and making it suitable for drinking.

Methods Of Rainwater Harvesting

There are two methods for rainwater harvesting. They are as follows:

  1. Surface runoff method
  2. Roof top method.

Let’s study both methods in detail below.

1. Surface Runoff Method

In this method, the rainwater which runs off along the surface of the land is collected in a tank which is kept below the surface of the ground. This water is utilized for irrigation and other such purposes.

The major drawback of the surface runoff method is that the rate of loss of water is high and the water is lost due to evaporation. So, effective and efficient methods of water conservation should be incorporated to minimize or eliminate the loss of water by evaporation. This method is relatively easy to adopt and use.

surface runoff rainwater harvesting
Surface runoff method

2. Rooftop Method

In this method, the rainwater is collected from the rooftops of various buildings and structures. The water collected by this method is collected either in a tank or it is diverted to artificial recharge systems. It is a very efficient and cost effective method for harvesting rainwater.

rooftop method of rainwater harvesting

The rooftop method for rainwater harvesting applies to the types of buildings listed below:

  • Residential buildings, bungalows, houses, villas.
  • Educational institutes such as schools and colleges.
  • Commercial buildings such as offices and commercial apartments.
  • Government buildings.
  • Industrial buildings.
  • Hotels, restaurants, resorts.
  • Swimming pools, stadium, etc.

There are various methods of using rooftop rainwater harvesting. They are as follows:

  1. Storage of direct use.
  2. Recharging groundwater aquifers.
  3. Recharging of bore wells.
  4. Recharge pits.
  5. Soakway or recharge shafts.
  6. Recharging of dug wells.
  7. Recharge trenches.
  8. Percolation tank.

Components Of Rainwater System

The basic components of rainwater harvesting systems are as given below:

1. Collection Area

The collection area is provided to collect the rainwater obtained from the rainfall. Water is collected on the roof surface itself and hence it is known as a collection area. Sometimes a tank is provided for the accumulation of the rainwater.

2. Conveyance System

The conveyance system is provided for the conveyance of water from the water collection area to the water storage area. The conveyance system comprises gutters or flat roofs, drainage holes, pipe systems, and downspouts.

3. Water Storage

It is a chamber or a tank in which the rainwater coming from the collection area is stored. The stored water is utilized when the need for water arises. The storage is located above or below the ground and it comprises either a single tank or multiple tanks.

4. Filtration System

A filtration system is provided to filter the water and to keep the debris out of the system. The rainwater cannot be used directly as it may contain harmful substances in it which may harm the people using it. The water stored as groundwater contains harmful elements like arsenic and salts. So the water is filtered before it is distributed and taken for use.

4. Distribution System

The water distribution system consists of the pipe system or the plumbing system through which the water is disturbed to the dedicated area for use such as house, office, schools, etc.

Benefits And Advantages Of Rainwater Harvesting

Rainwater harvesting is equally important for all. Below listed are some benefits:

1.. It is relatively easy to install, operate and maintain.

2. It ensures the fulfillment of the need for water for the future.

3. It is a cost-effective process.

4. It acts as an excellent source of water for irrigation.

5. The harvested rainwater is used during times of water crises.

6. It reduces flooding on road.

7. It reduces water bill and water consumption by as much as 40%.

Disadvantages Of Rainwater Harvesting

1. Due to unpredictable rainfall, the system’s efficiency may be affected.

2. The initial cost of rainwater harvesting system is relatively higher.

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