CBSE Class 10 · Water Resources

Rainwater Harvesting Class 10: Traditional and Modern Methods

Updated 14 October 2026 · Fact-checked

Rainwater harvesting is a socio-economically and environmentally viable alternative to big dams. Ancient Indians harvested rain, ground, river and flood water to suit local conditions: guls or kuls in the Western Himalayas, inundation channels in Bengal, khadins and johads in Rajasthan, and rooftop tankas in Bikaner, Phalodi and Barmer. Today rooftop harvesting is reviving in Tamil Nadu, Shillong and Gendathur.

Understand Rainwater Harvesting

Why rainwater harvesting. Because of the disadvantages of multipurpose projects and rising resistance to them, many saw water harvesting as a viable alternative, both socio-economically and environmentally. In ancient India, alongside hydraulic structures, there was an extraordinary tradition of water harvesting. People knew rainfall regimes and soil types deeply and developed techniques to harvest rainwater, groundwater, river water and flood water to suit local ecological conditions and needs.

Traditional methods by region.

Hill and mountain regions: diversion channels called guls or kuls in the Western Himalayas for agriculture. (Fig. 3.4: a kul leads to a circular village tank in Kaza village, from which water is released when needed.)
Rajasthan: rooftop rainwater harvesting to store drinking water was common.
Flood plains of Bengal: inundation channels to irrigate fields.
Arid and semi-arid regions: fields turned into rain-fed storage structures where water stands and moistens the soil: khadins in Jaisalmer and johads in other parts of Rajasthan.

Tankas of the Thar. In the semi-arid and arid parts of Rajasthan, especially Bikaner, Phalodi and Barmer, almost every house traditionally had an underground tank, a tanka, for drinking water.

Tankas could be as big as a room; one household in Phalodi had a tank 6.1 m deep, 4.27 m long and 2.44 m wide.
They were part of a well-developed rooftop system, built inside the house or courtyard and connected to sloping roofs by a pipe.
The first spell of rain was not collected, because it cleaned the roofs and pipes; later showers were stored.
Water lasted till the next rainfall, a reliable source when everything else dried up in summer. Rainwater, called palar pani, is considered the purest natural water. Some houses built underground rooms beside the tanka to keep cool.
Today rooftop harvesting is declining in western Rajasthan because the perennial Indira Gandhi Canal supplies plenty of water, though some households keep tankas because they dislike the taste of tap water.

Modern revival.

Tamil Nadu was the first state to make rooftop rainwater harvesting structures compulsory for all houses, with legal provisions to punish defaulters.
Shillong, Meghalaya: rooftop harvesting is the most common practice. Cherapunjee and Mawsynram, 55 km away, receive the highest rainfall in the world, yet Shillong faces acute water shortage. Nearly every household has a rooftop system, meeting about 15-25 per cent of its water needs.
Gendathur, Mysuru (Karnataka): a remote, backward village where nearly 200 households have installed rooftop systems and earned the rare distinction of being rich in rainwater. With 1,000 mm annual rainfall, 80 per cent collection efficiency and about 10 fillings, each house can collect and use about 50,000 litres a year.

How a modern rooftop system works (Fig. 3.3). Roof water is collected with a PVC pipe, filtered through sand and bricks, and taken by an underground pipe to a sump for immediate use. Excess water goes to a well, which recharges groundwater (recharge can also be through a hand pump or an abandoned dug well), and water can later be drawn from the well.

Related topic. Meghalaya's 200-year-old bamboo drip irrigation system, which taps stream and spring water, is covered on its own page.

Rainwater Harvesting: key facts

Why harvest rain: A socio-economically and environmentally viable alternative to multipurpose projects; Opening line.
Traditional methods: Guls/kuls (Western Himalayas); rooftop harvesting (Rajasthan); inundation channels (Bengal flood plains); khadins (Jaisalmer), johads (Rajasthan); Match method with region.
Tankas: Underground tanks in Bikaner, Phalodi, Barmer; linked to sloping roofs by a pipe; first spell not collected; palar pani = purest water; Phalodi tank: 6.1 m deep, 4.27 m long, 2.44 m wide.
Decline in western Rajasthan: Indira Gandhi Canal gives perennial water; Some keep tankas for taste.
Modern examples: Tamil Nadu: compulsory rooftop harvesting; Shillong: 15-25% of household needs; Gendathur (Mysuru): ~200 homes, ~50,000 litres per house per year; Case-question material.
Modern rooftop system: Roof -> PVC pipe -> sand and brick filter -> sump (use) -> excess to well -> groundwater recharge; Fig. 3.3.

How to answer Rainwater Harvesting questions

Expect MCQs matching methods to regions, 2-mark 'how were tankas used' questions, 5-mark 'traditional methods' answers and 4-mark cases on Shillong, Gendathur or Tamil Nadu.

1Start with why: harvesting is a viable alternative to dams, based on deep local knowledge of rain and soil.
2For traditional methods, give region plus method plus purpose (e.g., kuls in the Western Himalayas for agriculture).
3For tankas, explain the system: roof, pipe, underground tank, first rain left out, use in summer.
4For modern examples, use a number: Tamil Nadu (compulsory), Shillong (15-25 per cent), Gendathur (about 50,000 litres per house).
5For 'why it declined in Rajasthan', name the Indira Gandhi Canal.

Rainwater Harvesting in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Rooftop harvesting in a high-rainfall area

Suppose a hill town receives heavy rain for four months but runs short of water in the dry season, because rainwater rushes down the slopes and is lost.

Explain how rooftop rainwater harvesting could help, with an NCERT example.

Try it first, then show the solutionSolution

Identify the problem: rain is plentiful but not stored.
Describe the solution: collect roof water, filter it, store it or recharge groundwater.
Link to Shillong: despite nearby Cherapunjee and Mawsynram, Shillong faces shortage, and rooftop harvesting meets 15-25 per cent of household needs.

Answer: The town's problem is storage, not rainfall. Rooftop harvesting would collect rain from roofs through pipes, filter it, and store it in sumps or send excess to recharge wells. Shillong shows this works: though Cherapunjee and Mawsynram, 55 km away, get the world's highest rainfall, Shillong faces shortage, and rooftop systems now meet about 15-25 per cent of household water needs.

Memory hook: Catch the rain where it falls.

Tricks to remember Rainwater Harvesting

Short memory aids. Say each one aloud once, then use it on a question the same day.

Hills-Guls, Bengal-Channels, Desert-Khadins
Hill: Gul/Kul; Bengal: inundation channel; Jaisalmer: Khadin; rest of Rajasthan: Johad.
Use it when: Match-the-region MCQs.
BPB tankas
Bikaner, Phalodi, Barmer: 'Big Pots Below'.
Use it when: Tanka location questions.
First rain washes, second rain stays
The first spell cleans the roof and pipes; later rain is stored.
Use it when: Tanka process questions.
TN first
Tamil Nadu made it compulsory first.
Use it when: MCQs.

Rainwater Harvesting: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Khadins · 1 mark · MCQBoard level

Khadins, in which agricultural fields are converted into rain-fed storage structures, are found in:
(a) Bikaner
(b) Jaisalmer
(c) Shillong
(d) Mysuru

Try it first, then show the solutionSolution

NCERT names khadins in Jaisalmer and johads in other parts of Rajasthan (1 mark).

Answer: (b) Jaisalmer

Example 2: How tankas worked (2 marks) · 2 marks · Very short answerBoard level

Describe how rooftop rainwater was stored in tankas in Rajasthan. (2 marks)

Try it first, then show the solutionSolution

Tankas were underground tanks inside the house or courtyard, connected to the sloping roof by a pipe (1 mark).
Rain from the roof flowed down into the tanka; the first spell was not collected because it cleaned the roof and pipes (1 mark).

Answer: Tankas were underground tanks in the house or courtyard, linked to the sloping roof by a pipe, so roof rain flowed down into them. The first spell of rain was let go to clean the roof and pipes, and later showers were stored.

Example 3: Assertion-reason: decline in western Rajasthan · 1 mark · Assertion-reasonHarder board level

Assertion (A): Rooftop rainwater harvesting is declining in western Rajasthan.
Reason (R): The perennial Indira Gandhi Canal now provides plenty of water.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Try it first, then show the solutionSolution

NCERT links the decline directly to the canal's water (1 mark).

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Example 4: Traditional methods (5 marks) · 5 marks · Long answerHarder board level

'In ancient India there existed an extraordinary tradition of water harvesting.' Describe the traditional methods used in different regions and explain why they suited those regions. (5 marks)

Try it first, then show the solutionSolution

People knew rainfall regimes and soil types and harvested rain, ground, river and flood water to suit local conditions and needs (1 mark).
Hills: guls or kuls of the Western Himalayas diverted water for agriculture, suiting slopes with flowing water (1 mark).
Bengal flood plains: inundation channels used flood water to irrigate fields (1 mark).
Arid and semi-arid Rajasthan: khadins (Jaisalmer) and johads let water stand in fields and moisten the soil (1 mark).
Rooftop harvesting with tankas in Bikaner, Phalodi and Barmer stored drinking water till the next rainfall, vital where other sources dried up (1 mark).

Answer: People in ancient India knew local rainfall and soils well, so they harvested rainwater, groundwater, river water and flood water in ways that suited each region. In the Western Himalayas, diversion channels called guls or kuls carried water to fields on the slopes. In the flood plains of Bengal, inundation channels used flood water for irrigation. In arid and semi-arid Rajasthan, fields became rain-fed storage structures, khadins in Jaisalmer and johads elsewhere, where water stood and moistened the soil. In Bikaner, Phalodi and Barmer, houses stored roof rain in underground tankas, a reliable drinking supply until the next rains when other sources had dried up.

Example 5: Case: Gendathur · 4 marks · Case-basedHOTS / competency

Read the case and answer the questions.

Gendathur is a remote, backward village in Mysuru, Karnataka. Nearly 200 households there have installed rooftop rainwater harvesting systems, and the village has earned the rare distinction of being rich in rainwater. The village receives 1,000 mm of rain a year. With 80 per cent collection efficiency and about 10 fillings, each house can collect and use about 50,000 litres of water a year.

(i) In which state is Gendathur? (1)
(ii) How much water can each house collect in a year? (1)
(iii) What lesson does Gendathur offer to other villages facing water shortage? (2)

Try it first, then show the solutionSolution

(i) Karnataka (1 mark).
(ii) About 50,000 litres (1 mark).
(iii) Even a backward village with moderate rainfall can meet much of its need by collecting roof rain household by household (1 mark).
(iii) Simple, local, low-cost harvesting is a socio-economically and environmentally viable alternative to depending on big projects (1 mark).

Answer: (i) Karnataka. (ii) About 50,000 litres. (iii) Gendathur shows that even a remote, backward village with moderate rainfall can become water-rich if each household collects its roof rain. Simple, local and low-cost harvesting is a viable alternative to depending on big projects.

Example 6: Shillong's paradox (2 marks) · 2 marks · Very short answerHOTS / competency

Why does Shillong face acute water shortage although Cherapunjee and Mawsynram nearby receive the world's highest rainfall, and how do its people cope? (2 marks)

Try it first, then show the solutionSolution

High rainfall nearby does not mean stored water in the city; without storage, rain is lost and Shillong faces shortage (1 mark).
Nearly every household has rooftop rainwater harvesting, meeting about 15-25 per cent of its water needs (1 mark).

Answer: Heavy rain nearby does not mean water is stored for the city, so Shillong still faces shortage. Nearly every household has a rooftop harvesting system, which meets about 15-25 per cent of its water needs.

Where students lose marks in Rainwater Harvesting

The slips examiners see most often, and what to write instead.

Mistake: Mismatching methods and regions
Many local names.
Wrong working
Khadins are found in Bengal.
Right working
Khadins: Jaisalmer; inundation channels: Bengal; kuls: Western Himalayas.
Do this: Use the region-method table.
Usually costs: 1 mark.
Mistake: Saying tankas collect all rain
The first-flush detail is missed.
Wrong working
All rainwater from the roof went into the tanka.
Right working
The first spell cleaned roofs and pipes and was not collected.
Do this: Remember 'first rain washes'.
Usually costs: 1 mark.
Mistake: Wrong reason for decline in Rajasthan
Students guess 'people forgot'.
Wrong working
Tankas declined because people became modern.
Right working
The perennial Indira Gandhi Canal now provides plenty of water.
Do this: Name the canal.
Usually costs: 1 mark.
Mistake: Answering only with modern methods
Ignoring the traditional half of the topic.
Wrong working
Rainwater harvesting uses PVC pipes and filters.
Right working
Include guls, kuls, inundation channels, khadins, johads and tankas.
Do this: Read whether the question says 'traditional'.
Usually costs: 2-3 marks.

Exam tips

Make a table of method, region and purpose: it answers most MCQs and the 5-mark question.
Quote one number in case answers: 15-25 per cent (Shillong) or 50,000 litres (Gendathur).
Remember Tamil Nadu as the first state with compulsory rooftop harvesting.
There are no map items on rainwater harvesting; the water map list covers only dams.

Practice questions on Rainwater Harvesting

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which state was the first to make rooftop rainwater harvesting compulsory for all houses?
(a) Rajasthan
(b) Meghalaya
(c) Tamil Nadu
(d) Karnataka
Hint
It also punishes defaulters.
Answer
(c) Tamil Nadu
Q2 · 2 marks · Very short answerBoard level
What are guls or kuls? Where are they found? (2 marks)
Hint
Hills.
Answer
Guls or kuls are diversion channels built in the hill and mountainous regions of the Western Himalayas to carry water for agriculture; a kul may lead to a village tank.
Q3 · 2 marks · Very short answerHarder board level
Why was rainwater called 'palar pani' considered so valuable in the Thar? (2 marks)
Hint
Purity and reliability.
Answer
Palar pani was considered the purest form of natural water. Stored in tankas, it lasted till the next rainfall, so it was a reliable drinking source in summer when other sources dried up.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): In tanka systems, the first spell of rain was not collected.
Reason (R): The first rain cleaned the roofs and the pipes.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Hint
Think of dust on the roof.
Answer
(a) Both A and R are true, and R is the correct explanation of A.
Q5 · 5 marks · Long answerHOTS / competency
Suppose your school wants to install a rooftop rainwater harvesting system. Using NCERT's Fig. 3.3, describe the stages from the roof to groundwater, and give one reason the school should do it. (5 marks)
Hint
Pipe, filter, sump, well, recharge; then scarcity.
Answer
Rain falling on the roof is collected using a PVC pipe and passed through a filter of sand and bricks to clean it. An underground pipe carries the filtered water to a sump for immediate use. Excess water from the sump is taken to a well, through which it recharges the underground water; the well can later supply water. Recharge can also be done through a hand pump or an abandoned dug well. The school should do it because water scarcity is mostly caused by over-exploitation of groundwater; harvesting reduces dependence on pumping and replenishes groundwater, as Tamil Nadu, Shillong and Gendathur show.
Q6 · 2 marks · Very short answerHOTS / competency
Evaluate why rainwater harvesting is considered a better alternative to multipurpose projects by many people. (2 marks)
Hint
Problems of dams; strengths of local methods.
Answer
Dams face rising resistance because of displacement, submergence and ecological harm. Rainwater harvesting is local, suited to local rainfall and soils, and is socio-economically and environmentally viable, so many see it as a better alternative.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.What are johads?Show answer
Rain-fed storage structures in fields in parts of Rajasthan.
2.In which towns did almost every house have a tanka?Show answer
Bikaner, Phalodi and Barmer.
3.What were the dimensions of the Phalodi tank in NCERT?Show answer
6.1 m deep, 4.27 m long and 2.44 m wide.
4.How far are Cherapunjee and Mawsynram from Shillong?Show answer
About 55 km.
5.How many households in Gendathur installed rooftop systems?Show answer
Nearly 200.

Rainwater Harvesting: frequently asked questions

What is rainwater harvesting in Class 10 Geography?

Collecting and storing rainwater, groundwater, river or flood water using methods suited to local conditions, seen as a viable alternative to big dams.

What are the traditional methods of rainwater harvesting?

Guls and kuls in the Western Himalayas, rooftop harvesting and tankas in Rajasthan, inundation channels in Bengal, and khadins and johads in Rajasthan.

What are tankas?

Underground tanks in houses of Bikaner, Phalodi and Barmer that store rooftop rainwater for drinking until the next rainfall.

Which state made rooftop rainwater harvesting compulsory first?

Tamil Nadu, with legal provisions to punish defaulters.