Rainwater Harvesting | Components, Methods, Importance, Types, Advantages

Rainwater Harvesting – Explained

This article intends to inform you about the rainwater harvesting system. For a better understanding, the components of the system and its methods have been mentioned.

Know more about it through its importance, types, advantages, and disadvantages. Figure out the best way for you as well.

The problem scarcity of water has become ardent in several countries. In India, various rural and urban settlements are dealing with the problem.

This has paved the way for growing concerns to figure out ways to save water. One of them is the rainwater harvesting system.

What is Rainwater Harvesting?

Rainwater harvesting refers to a technique of collection or storage or harvest of rainwater into natural reservoirs or tanks for future use rather than allowing it to run off.

In other words, rainwater harvesting is defined as the simple process or method or technology which is used to conserve rainwater by the process of storing, collecting, conveying and purifying of rainwater that runs-off from various surfaces for later use.

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What are the components of a rainwater harvesting system?

In the rainwater harvesting system, there are various components that are used at various stages of success transporting rainwater, filtration, and storage.

The components involved in a rainwater harvesting system are as follows:-

Catchments

The area which directly receives rainfall and provides the water to the system further is the catchment. A catchment can be a paved area like a courtyard or terrace of a house or building.

It can also be an area like an open ground or a lawn. For rainwater harvesting, often roofs or areas made of reinforced cement concrete, corrugated sheets, or galvanized iron are used.

Coarse mesh

The coarse mesh is a net that prevents the passage of big chunks of debris or other material from the catchment area to the further system.

This ensures that any visible impurities are prevented from getting into the system and contaminating the water.

Gutters

Gutters are the channels which are placed all around the edge of the catchment or sloping roof.

It collects and transports rainwater to the storage unit or tank. They can of different shapes like semi-circular, rectangular, etc.

They can be made using different materials like:-

  • Locally available material such as plain galvanized iron sheets
  • Cutting PVC material into desired shapes
  • Bamboo or betel trunks

The size of these channels depends on the flow during the highest recorded intensity or amount of rain.

It is always best to over-size them to support heavy rainfall and water flow. This is because the amount or intensity of rainfall cannot be predicted accurately.

However, they can fall off when loaded with water. They need to be supported or welded into the roof to ensure a smooth flow and efficient system.

Conduits

The drains or pipelines which have the work to carry rainwater from the catchment or rooftop area to the harvesting system are conduits.

They can be made of any commonly available material like galvanized iron or polyvinyl chloride.

The diameter of pipe installed depends on the intensity of rainfall.

First-flush

It is a valve that ensures that the water from the first rainfall does not enter the system and is flushed off.

This is done as the water from the first rain has a relatively larger amount of pollutants.

Filters

Filters are used to eradicate the pollutants available in water collected from the catchment area.

The filter unit is a chamber that has filtering elements which are coarse sand, gravel, fiber, and charcoal.

It removes the debris and dirt from the water before it enters the storage unit or recharge structure.

There are two most prominently types of filters used which are:-

  • Sand Filter which has sand and gravel places in layers for filtration purposes.
  • Charcoal Filter which has layers of gravel, sand, and charcoal. Charcoal is added to provide additional filtration of the water.

Storage tanks

The tanks or units where the rainwater is ultimately stored are the storage tanks or units. These can be of various shapes, materials and sizes depending upon the requirement.

The shapes sued are rectangular, square and cylindrical. The construction materials often used are plastic, reinforced cement concrete, metal sheets etc.

Also, they can be placed depending on space availability. Also, it requires maintenance measures to be ensured beforehand.

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What are the methods of rainwater harvesting?

In most of the areas, there are two most prevalent methods used which are as follows:-

Surface run-off rainwater harvesting

Under this method, the rainwater which flows or runs of in the urban areas is collected and stored to recharge the groundwater level or the aquifer bed.

This is done instead of letting the water flow into the drains. Alongside this, it improves the levels and quality of the groundwater.

Rooftop rainwater harvesting

In the rooftop rainwater harvesting method, the rainwater is directly collected from the roof all surfaces of the buildings and is transported into storage tanks or artificial aquifers.

The water harvested or stored through this method can be used for daily purposes along with recharging the aquifers and helping restore the groundwater level.

What are the types of rainwater harvesting systems?

Depending on the need, requirements and the target catchment area, there are several possible configurations and degrees of complexity and arrangement of a rainwater harvesting system.

Based on the way the rainwater is pumped, the rainwater harvesting system is of the following types:-

Water Butt

This is one of the most basic forms of rainwater harvesting system where the water is collected in the container from the drain pipes and/ or the natural rainfall. The water collected is usually used for gardening purposes.

Direct Pumped

There are two methods used under this type of rainwater harvesting system which is as follows:-

Submersible

Most commonly used for domestic purposes, in this type of rainwater harvesting system, the pump is located within the underground tank. The harvested water is pumped directly into the WCs or other appliances.

Suction

Located within a control unit within the establishment, in this type the unit deals with the backup from main water supply. In this, there is no need to send main water down to the tank.

Indirect Gravity

Under the indirect gravity system, the harvested rainwater is first pumped into a high level tank (header tank).

It is then allowed to supply the outlets by gravity alone. By this arrangement, the pump is only required to work when the header tank needs to be filled.

Indirect Pumped

Under this, the harvested rainwater is first formed to a tank. This tank can be placed at any level in the building and does not depend on the gravity to supply the outlets.

A booster pump is installed to provide a pressurized supply and employees the benefit of not having to feed the mains backup water to the underground tank.

This offers great flexibility due to the booster pumps being tailored to meet the flow and pressure requirements of the building.

Gravity Only

In certain circumstances, it is possible to have a rainwater harvesting system that functions solely through gravity.

The gravity only type of rainwater harvesting system is only possible when the storage tank is located below the gutter levels.

However, it should be higher than the outlets that it will supply. In this system, only gravity is needed to collect and filter water for various purposes of home-usage.

Hence, this serves as an ultra-energy-efficient option.

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What is the importance of rainwater harvesting?

Owing to the current conditions, it is not long before the price and availability of water would be more valuable and precious.

Due to this, rainwater harvesting has become essential and important due to the following reason:-

  • Rainwater harvesting to recharge the groundwater level is better for the environment and the planet.
  • It helps you and lowering your utility bills by collecting and harvesting rainwater and storing it in the thanks by reducing dependency on municipal water supply.
  • It will ensure the availability of water whenever you need it regardless of any adverse situations like supply cut-off or shortage of water.
  • Rainwater has been the source of growth for the environment and ecosystem for millions of years. Therefore, it is better for gardening as well as it is relatively pure and free from toxin.
  • The collected rainwater reduces flooding and helps in decreasing soil erosion by reducing the chances of run-off during the times of heavy rainfall.
  • Setting up and installing a rainwater harvesting system is very easy and cost-effective. Moreover, it allows quick access to the stored water once collected.
  • It serves as a sustainable and eco-friendly practice which reduces the carbon footprint and promotes environmental-friendly method.

What are the disadvantages of rainwater harvesting?

Rainwater harvesting can be a great way to save and conserve water. Having a rainwater harvesting system has several benefits as well.

However, it has certain downfalls too which are as follows:-

Rainfall cannot be predicted accurately

The amount of rainfall is different in places. It isn’t possible to accurately predict the time and amount of rainfall.

Complete dependency to fulfill your daily needs can cause trouble when there’s no or less rainfall.

Requires regular maintenance

Rainwater harvesting systems can support algae growth, mosquitoes, insects, lizards and even rodents which contaminate the stored water.

They need to be properly and regularly cleaned and maintained to avoid such things which can be overwhelming.

Incurs high-cost initially

The initial installation cost depends on the system’s size and technology used. The recovery of investment cannot be predicted by a rainwater harvesting system.

Chemical seepage or animal dropping issues

There can be problems of chemical seepage and animal dropping from certain roofs. This is harmful when consumed or used for watering plants.

Limited storage

The storage of rainwater is restricted or limited by the size of the tanks and time of rainfall and its usage as well.

Is rainwater drinkable?

The rain goes through the atmosphere before it touches the ground. This gives birth to the possibility that it can pick contaminants from the air and atmosphere.

The possibility of being the rainwater safe for drinking is sometimes.

  • Rainwater near nuclear or chemical plants, mills, industries, etc, in no way, is safe to drink. It could have picked up toxic chemicals from the surfaces before being harvested.
  • However, rainwater serves as a source of water supply for a significant population across the world. The possibility of pollens, pollutants, and other contaminants being available is lower than the water supply people have.
  • Rainwater can be treated and made safe to drink. Boiling and filtration can be done to improve the quality of rainwater and make it worth consuming.

Which rainwater harvesting system is best for you?

The suitability of the best rainwater harvesting system depends on the individual situation and needs.

In case of limited internal space availability or impossibility fit a header tank; the direct pump systems prove to be the best for domestic purposes.

In the possibility to use a high level headed tank, the indirect gravity option is preferable where there is no requirement for the system to supply at high pressure.

In the requirements of high pressure, the indirect pump system serves to be the most appropriate one.

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