Rainwater Harvesting, Practice Problems and FAQs

Can you think of a life without water? None of us can. You must be wondering, water covers 71 percent of the earth’s surface then why would we need to think of a life without water? We have plenty of water on earth. But the reality is that only 0.5 percent of the water on earth is suitable for our use. Suddenly the scenario seems a lot more grim, doesn’t it? 

This indicates that we cannot afford to waste water. But sadly, people have been wasting water thinking that it's a never-ending resource and currently many regions of the world are facing serious problems of water scarcity. Thus, conservation of water is of utmost importance in the current scenario.

Apart from the water bodies, can you think of a natural source of water? Yes, it is the rain water! It is the purest form of water we can get. But we cannot directly use the rainwater, since it is mixing up with the atmospheric impurities. So there should be a technique by which we can use rain water in its finest form. Rainwater harvesting system is the solution for this. So now we are going to discuss more about the rainwater harvesting system, its techniques, advantages and disadvantages.

Table of contents

• Rainwater harvesting 
• Purpose of rainwater harvesting
• Advantages of rainwater harvesting system
• Disadvantages of rainwater harvesting system
• Quality of rainwater in rainwater harvesting systems
• Practice Problems
• FAQs

Rainwater harvesting

Rainwater harvesting is the process or technology used to conserve rainwater. It is also known as rainwater catchment system or rainwater collecting system. It is a technique that gathers and stores rainwater for human usage. Rainwater catchment systems can be as simple as small buckets or complex structures having containers, propellers, and purifying systems. 

So how will we harvest rainwater? What is the process of it? Let’s check it out.

Parts of rainwater harvesting system

There are five parts for the rain water harvesting system. They are catchment, conveyance system, flush, filter, tanks and recharge structures. Now let’s see what these are.

Catchment is a structure used to collect and store rainwater. Conveyance system transports collected water from the catchment area to the recharge zone. Flush gets rid of the initial round of rain. Filter is a device used to filter collected rainwater and remove the contaminants. Tanks and recharge structures are for holding ready-to-use filtered water.

So, rainwater harvesting is the act of collecting and storing rainwater that flows from natural or artificial catchments, using intentionally constructed systems. Such areas can be rooftops, complexes, rock surfaces, hill slopes, and artificially repaired impermeable or semi-pervious land surfaces.

Factors influencing the water harvesting system

Several factors influence the amount of water collected. Some of the factors are the amount of runoff, the type of catchment, the environmental conditions, the availability of technology, capacity of storage tank, types, slopes, and material of the roof. Rainfall amount, its frequency, and quality also influence the harvesting system. The ease with which rainwater enters the subsurface and recharges the groundwater also plays an important part.

Purpose of rainwater harvesting

Rainwater harvesting helps to conserve natural water and can be useful in alleviating the rising concern of water scarcity around the globe. The harvested rainwater can be used to irrigate gardens, do laundry, wash vehicles, flush toilets, bathe humans and animals and can also be used for human consumption. 

Advantages of rainwater harvesting system

Rainwater harvesting is a less expensive and simple method of water conservation that aids in the reduction of the water bill, reduces the need for water from water bodies and lessens the demand for imported water. It does not require elaborate infrastructure. It encourages water and energy conservation and enhances both the quality and quantity of groundwater. Harvested rainwater can be used to irrigate agricultural lands without the use of a filtration system as it does not contain any chemicals or dissolved salts and is mineral-free. It minimises soil erosion, floodwater runoff, floods, and surface water contamination caused by fertilisers, pesticides, metals, and other sediments. Rainwater collecting systems can provide water even during dry seasons while reducing demand on municipal systems.

Disadvantages of rainwater harvesting system

Aside from the numerous benefits, the rainwater collecting system has a few drawbacks, such as unexpected rainfall, a lack of a suitable storage system, etc. It requires time, effort and money for proper and regular maintenance. Installation of this system requires technical knowledge and cannot be done by all. The system might fail in case of little or no rainfall. If not placed correctly and maintained, it can be the breeding ground for mosquitoes and other water-borne pathogens. It requires efficient storage strategies and sufficient storage provisions for optimum benefits.

Quality of rainwater in rainwater harvesting systems

Separating the initial rush of rainfall from the roof, gutters, and other collection surfaces can improve the water quality in the rainwater storage tank. Rainwater collected from polluted surface runoffs is not suitable for drinking or cooking, but in order to use it for gardening and agricultural purposes, it needs to be cleaned appropriately. Solar water disinfection or chlorine or other chemicals can be used to disinfect pre-filtered water. This will help to eliminate the pathogenic microorganisms in the water. To bind small suspended particles into larger particles that can be removed by settling and filtering, a liquid alum solution can be added to the incoming raw water.

Practice Problems

Q 1. Given below are some statements regarding the rainwater harvesting system. Find out the correct statement from it.

a. Rainwater harvesting is a technique that gathers and stores rainwater for human consumption. 
b. It is also known as rainwater catchment system or rainwater collecting system
c. Catchment is a structure used to collect and store rainwater.
d. Rainfall amount, its frequency, and quality do not influence the harvesting system. 

1. A,B,C,D
2. A,B,C
3. A,C
4.  ONLY
Answer: Several factors influence the rainwater harvesting system. Some of the important factors are the rainfall amount, its frequency, and quality of rainwater. The ease with which rainwater enters the subsurface and recharges the groundwater also plays an important part. Apart from these, the amount of runoff, the type of catchment, the environmental conditions, the availability of technology, capacity of storage tank, types, slopes, and material of the roof also determine the amount of water harvested. So the statement D is incorrect.

Hence the correct option is b.

Q 2. Which of the following parts of a rainwater harvesting system helps to get rid of the initial round of rain?

a. Flush
b. Catchment
c. Conveyance system
d. Filter.
Answer: Catchment is a structure used to collect and store rainwater. Conveyance system transports collected water from the catchment area to the recharge zone. Flush gets rid of the initial round of rain. Filter is a device used to filter collected rainwater and eliminate contaminants. Tanks and recharge structures are for holding ready-to-use filtered water.

Hence the correct option is a. 

Q 3. What are the uses of harvested rainwater?
Answer: Harvested rainwater can be used for irrigation, washing clothes, vehicles and utensils, bathing, gardening, for flushing toilets, for cooking and for human consumption.

Q 4. What are the advantages of the rainwater harvesting system?
Answer: Some of the advantages of a rainwater harvesting system are: 

• Rainwater harvesting is a less expensive and simple method of water conservation 
• It helps to reduce the water bill, the need for water from water bodies and lessens the demand for imported water. 
• It does not require elaborate infrastructure. 
• It encourages water and energy conservation and enhances both the quality and quantity of groundwater. 
• Harvested rainwater can be used to irrigate agricultural lands without the use of a filtration system as it does not contain any chemicals or dissolved salts and is mineral-free. 
• It minimises soil erosion, floodwater runoff, floods, and surface water contamination caused by fertilisers, pesticides, metals, and other sediments. 

FAQs

Q 1. Who in India developed rainwater harvesting?
Answer: Rainwater collection has been documented in China as far back as 6,000 years. Rainwater collection has been documented since at least 4,000 BC. Amla Ruia, also known as 'Water Mother,' was the first to introduce it to India. She is a social activist from Mumbai who developed a water-saving solution using traditional water gathering methods. Rajasthan was plagued by a severe drought in the summer of 2000, which resulted in poor agricultural output as most crops perished owing to a lack of water. Amla Ruia established the Aakar Charitable Trust to provide a long-term solution to the water crisis in Rajasthan, inspired by the dismal conditions of the farmers. Although the government gave water to the villages via water tankers, it was not a long-term solution.

Q 2. Who is the father of rainwater harvesting?
Answer: Rajendra Singh is an Indian environmentalist and water conservationist from Rajasthan's Alwar district. He got the Magsaysay Award in 2001 and the Stockholm Water Prize in 2015. He is also regarded as the "waterman of India." He is the founder of the 'Tarun Bharat Sangh' (TBS), an NGO that was created in 1975. The NGO, based in village hori-Bhikampura in Thanagazi tehsil, near Sariska Tiger Reserve, has been instrumental in combating the slow bureaucracy and mining lobby, and has assisted villagers in taking charge of water management in their semi-arid area, which is close to the Thar Desert. They did it through the use of johad, rainwater storage tanks, check dams, and other time-tested and path-breaking techniques. 

Q 3. What makes rainwater so clean?
Answer: Rainwater is the finest source of natural water. Rainwater is produced through condensation of water in the presence of the sun. The water in lakes, rivers, and oceans evaporates. During the evaporation process, all pollutants are removed. The evaporated water condenses around atmospheric particles and gradually forms clouds. When clouds become heavy, the condensed water droplets fall directly onto the earth as rain.

Q 4. What is the expense of making a rainwater harvesting system?
Answer: Rainwater harvesting technologies are site specific, making it difficult to provide a cost estimate. But first and foremost, the two most important components of a rainwater harvesting system - rain and catchment space - are both free. The pipe connections would account for a significant amount of the costs. This could be significantly reduced by judiciously repairing roof slopes and the location of rainwater exits. The cost, however, varies significantly depending on the availability of existing structures such as wells and tanks that can be converted and used for water collection. Installing a water harvesting system in a building typically costs between Rs 2,000 and 30,000 for buildings of 300 square metres. 

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