An Introduction to Rainwater Harvesting

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All living things, including animals, plants, besides human beings, need water to live and carry out different activities. Can you imagine or visualize your day without water? It is unthinkable. We use water for various day-to-day activities, such as bathing, cooking, cleaning, washing, drinking, and other domestic and industrial uses. So do farmers need water (watering plants) for their agricultural activates. Hence there is an urgent need to encourage rainwater harvesting to conserve water (save water) for irrigation.

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Water is a precious, essential component of the ecosystem. In recent times, we all are heading toward the scarcity of water. Water covers about 71 per cent of the Earth’s surface, and the oceans hold about 96.5 per cent of all Earth’s water. Comparatively, the share of freshwater is significantly less. Rainwater harvesting is a water conservation technique that has been in practice since ancient times.

In this article, we present all the things you should know about rainwater harvesting.

What is Rainwater Harvesting?

Water is the most precious natural resource. Earth is the only planet in the universe that has water. The problem is that most of us take it for granted.  There has been an increased awareness about the importance of water for our survival and its limited supply. Especially, this holds in dry continents such as Australia. Rainwater harvesting is collecting and storing rainwater for reuse on-site and prevent it from running off. Subsequently, this stored water is used for various purposes, such as gardening and irrigation.

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The harvesting of rainwater involves the collection of water from surfaces on which rainfalls. Subsequently, this water is  collected from the roofs of buildings and stored in rainwater tanks. This is a widespread practice, especially in rural Australia. Dams can also collect the water falling on the ground.

Consequently, whichever way the water collection takes place, it is precious. There are two basic ways of harvesting rainwater: rooftop rainwater harvesting and surface runoff rainwater harvesting.

Surface Runoff Harvesting

In urban areas, rainwater gets wasted when it flows away as surface runoff. This runoff can be prevented and used for recharging aquifers by adopting appropriate methods.

Rooftop Rainwater Harvesting

It is a system of catching rainwater when it falls on the buildings. In rooftop harvesting, the roof becomes the water catchment area.

Usage of Harvested Rainwater

A rainwater harvesting system  distributes water for irrigation and potable use.  In urban areas, rainwater collection takes place to supplement irrigation needs. However, in rural areas, the system supplies the whole household with drinking water.  Rainwater harvesting systems are also used for storm water management purposes as green infrastructure.

Why Do We Need Rainwater Harvesting?

Rainwater harvesting is becoming popular for two primary reasons, namely:

  1. It provides superior water quality and 
  2. A desire to reduce the use and dependence on locally supplied treated water for all of our daily needs. 

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Rainwater is soft as well as pure. It is free from minerals, salts, and other artificial and natural contaminants. Additionally, rainwater harvesting is the easiest method for water conservation. This reduces the amount of water that requires treatment by the local water treatment plant and delivered to the service area.

  • Rainwater is absolutely free. You only need to pay for the expenditure for building the collection system infrastructure. 
  • Rainwater harvesting is an environmentally responsible and socially acceptable practice since it promotes self-sufficiency and helps conserve water.
  • You can reduce the usage of the local water supply, thereby leading to a reduction of utility bills.
  • You can use it as a main water source or as a backup source for wells and local water supply. 
  • They can also be very helpful in times of emergencies.
  • Rainwater harvesting systems provide you with total control over your water supply (ideal for cities with water restrictions).
  • You can easily install them on existing structures. You can build them during the construction of the new building. 
  • They are very modular and flexible in nature, allowing expansion, reconfiguration, or relocation.
  • Rainwater is the best water source for landscape irrigation as it lacks chlorine and other treatment chemicals.
  • The harvested water is for local use as it is close to the collection source. This reduces the energy required for moving water around our cities.
  • Rainwater harvesting can significantly reduce storm water pollution, thereby lessening its impact on our local watersheds.

Primary Components of a Rainwater Harvesting System

Rainwater harvesting systems comprises the following components:

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  • Catchment section-  The surface that receives rainfall directly is the catchment of the rainwater harvesting system. It can be a terrace, courtyard, or paved or unpaved open ground. The terrace may be a flat stone roof or sloping roof. 
  • Conveyance or transportation system – Rainwater from the rooftop should be carried down by the water pipes or drains to the storage system. Water collection takes place through gutters from sloping roofs and transported down the pipe. The mouth of each drain on the roof or terrace should have wire mesh to restrict floating material.
  • First Flush- It is used for flushing out the first spell of rain. This is done to avoid contaminating storable water by the probable contaminants of the atmosphere and the catchment roof. Additionally, it helps in the cleaning of silt and other material deposited on the roof during dry seasons. It would help if you made provisions for the first rain separators at the outlet of each drainpipe.
  • Filter – They are used for filtering the collected rainwater and removing pollutants. Otherwise, there are chances of rainwater contaminating groundwater. Filters  remove turbidity, color, and microorganisms effectively. After the first flushing of rainfall, water should pass through filters placed on top of the storage tank. Consequently, this filter keeps the rainwater in the storage tank clean. It prevents silt, dust, leaves, and other organic matter from entering the storage tank. Consequently, you must clean the filter media daily after every rainfall event.  Otherwise, the clogged filters prevent rainwater from easily entering the storage tank, and the filter may overflow.
  • Storage systems: These are used for storing filtered water, which is ready to use.

How to Harvest the Rainwater?

The rainwater harvesting process involves collecting and storing rainwater with the help of artificially designed systems that run off naturally or man-made catchment areas. The man-made catchment areas include the rooftop, rock surface, hill slopes (contour ploughing), and compounds. Consequently, there may be several factors that play a vital role in the amount of water harvested. Some of these factors are:

  • Features of the catchments.
  • Impact on the environment.
  • Availability of the technology.
  • The quantum of runoff.
  • The frequency,  quantity and quality of the rainfall.
  • Types of the roof, its slope and the materials.
  • The capacity of the storage tanks.
  • Speed and ease with which the penetration of rainwater takes place through the subsoil to recharge the groundwater.

Benefits of Rainwater Harvesting

The benefits of the rainwater harvesting system are listed below.

  • Rainwater harvesting is the cheapest option for water conservation. Additionally, it incurs only a one time cost for the set-up.
  • It helps in the reduction of the monthly water utility bill.
  • Decreases the water demand.
  • It promotes the conservation of both energy and water.
  • Improvement in quality and the quantity of groundwater.
  • Simple, easy to install and operate.
  • It reduces soil erosion, storm water runoff, and flooding.
  • Rainwater harvesting system reduces pollution of surface water with fertilizers, pesticides, metals and other sediments.
  • It is an excellent water source for landscape irrigation. Particularly since water is free from chemicals and dissolved salts.
  • It significantly reduces our reliance on water storage dams. Consequently, this places reduced stress on these dams. This can potentially reduce the need to expand these dams or build new ones.
  • Water collection by rainwater harvesting systems reduces the flow of storm water. Consequently, this reduces overloading the storm water systems in our neighborhoods.

Disadvantages of Rainwater Harvesting

Although there are lots of advantages of the rainwater harvesting system, there are also some disadvantages. However, the number of benefits weigh much more than the number of disadvantages. Some of the disadvantages are as follows:

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  • Unpredictable rainfall will affect the water collection.
  • It requires regular maintenance.
  • Unavailability of the proper storage systems.
  • The installation requires some technical skills.
  • The supply of rainwater can get restricted due to limited or no rainfall.
  • If not installed correctly, it may attract the carriers of waterborne diseases.
  • One of the significant drawbacks of the rainwater harvesting system is storage limits.

Conclusion

The ancient practice of rainwater harvesting still holds many benefits and value for our modern times. It provides us with an alternative water source. The rainwater harvesting system supports water conservation. It has been in practice for many years. Today, the scarcity of good quality water has become a significant cause of concern. It gives you control to operate the system as you see fit.

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The importance of rainwater harvesting lies in the fact that the water can be stored for future use. Just as it can be used directly, the stored water can also be utilized to revitalize the ground level water and improve its quality. This also helps to raise the level of groundwater, which then can be easily accessible. Rainwater collection can also teach valuable lessons in water conservation. This is important as our freshwater resources are getting stretched further day by day.

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