A dam is a wall built across a river to hold back water. India has many famous dams, each with a record. This article explains the tallest and longest dams of India in simple words.
Dam size is only one part of the story. Read Dam Failures in India to see how breaches happen and how warnings protect people downstream.
mcqquestion.com · General Knowledge🏙 Water Walls
🏙 Dams of India
India’s tallest and longest dams
Tehri260.5m, tallest, Bhagirathi
Bhakra225m, Sutlej, Himachal
Hirakud25.8km, longest, Mahanadi
Sardar Sarovar138.68m, Narmada, Gujarat
Nagarjuna Sagar124m, Krishna, largest masonry
Idukki168.91m, Periyar, arch dam
💡India’s tallest dam and longest dam are different structures on different rivers. Height and length do not go together.
General Knowledge · GK0022tall & long
Must Know
What Is a Dam
- WhatA dam is a strong wall built across a river to stop and store its water.
- WhyStored water is used for drinking, farming and making electricity.
- HowThe dam holds water in a lake behind it, and the water flows out through pipes when needed.
- ExampleThink of a dam like a plug in a huge bathtub, holding water until you pull it out.
The Tehri Dam, and The Bhakra Nangal Dam, and The Hirakud Dam
- WhatThe Tehri Dam on the Bhagirathi River in Uttarakhand is India’s tallest dam, at 260.5 metres.
- WhyIt is important because it gives water and electricity to many people in north India.
- HowIt stores the river water high up in the Himalayas and uses it to run power turbines.
- ExampleA 260-metre wall is like stacking about 86 floors of a building on top of each other.
- WhatThe Bhakra Nangal Dam on the Sutlej River in Himachal Pradesh stands 225 metres tall.
- WhyIt is important because it waters large farmlands in Punjab and Haryana.
- HowIt stores the river water and sends it through canals to fields far away.
- ExampleIt is sometimes called the foundation of the Green Revolution because of the water it supplies to farms.
- WhatThe Hirakud Dam on the Mahanadi River in Odisha is India’s longest dam, at 25.8 kilometres.
- WhyIt is important because it controls floods and stores water for farming.
- HowIt is a long earthen dam, made of soil and rock, that holds back the river.
- ExampleIt is the longest earthen dam in the whole world, like a giant earth wall across the river.
Good to Know
The Sardar Sarovar Dam
- WhatThe Sardar Sarovar Dam on the Narmada River in Gujarat stands 138.68 metres tall.
- WhyIt is important because it gives drinking water to many towns and cities.
- HowIt stores the Narmada’s water and sends it to dry areas through canals.
- ExampleIt is one of the largest dams in India in terms of the water it can hold.
- Four StatesThe project actually spans four states: Maharashtra, Madhya Pradesh, Gujarat, and Rajasthan. It supplies drought-prone areas of Gujarat and Rajasthan, not Gujarat alone.
The Nagarjuna Sagar Dam, and The Idukki Dam, and Ancient Hydraulic Structures, and Why Dam Facts Are Asked
- WhatThe Nagarjuna Sagar Dam on the Krishna River sits on the border of Telangana and Andhra Pradesh.
- WhyIt is important because it is the world’s largest masonry dam currently in operation.
- HowA masonry dam is built with stone and mortar, and this one stands 124 metres tall.
- ExampleIt waters large areas of farmland in the two states using its stored river water.
- WhatThe Idukki Dam on the Periyar River in Kerala is 168.91 metres tall.
- WhyIt is important because it is a famous arch dam that produces electricity.
- HowAn arch dam is curved, and its curve pushes the water’s force into the rock walls on both sides.
- ExampleThink of a door arch that holds a heavy roof — the curved shape makes the dam very strong.
- SringaverapuraNear Allahabad, a sophisticated first-century BC water-harvesting system channelled flood water from the Ganga.
- Mauryan EraDams, lakes and irrigation systems were built extensively during the reign of Chandragupta Maurya.
- Bhopal LakeBuilt in the 11th century, it was one of the largest artificial lakes of its time.
- Hauz KhasSultan Iltutmish built this 14th-century tank in Delhi, to supply water to the Siri Fort area.
- WhatExams ask which dam is tallest, longest or on which river.
- WhyThese are clear facts that are easy to test.
- HowYou should connect each dam to its river, state and record.
- ExampleFor example, Tehri goes with the Bhagirathi and the record of being tallest.
✅ Test Yourself
Work through a 5-question chain on Dams of India, then keep practising with a random General Knowledge question.
Great to Know
Tallest versus Longest
- WhatThe tallest dam, Tehri, is not the longest, and the longest, Hirakud, is not the tallest.
- WhyHeight and length measure two different things, so they do not go together.
- HowHeight is how high a dam rises; length is how wide it stretches across the river.
- ExampleA tall tower and a long wall are both big, but in different ways — just like these two dams.
- So whatRemember which record belongs to which dam.
How Dams Help Us
- WhatDams help us in three main ways: water, farming and electricity.
- WhyWithout dams, much of India’s rainwater would flow away unused.
- HowDams store the water, send it to fields, and use its force to make power.
- ExampleThe water stored behind a dam is like money saved in a bank for later use.
- So whatDams turn river water into useful resources.
- Nehru’s QuoteJawaharlal Nehru called dams the “temples of modern India.” He meant they would drive both farm growth and industrial progress after independence.
Types of Dams, and Reservoirs in Exams, and How Dams Hinder Navigation, and The Silt Problem
- WhatDams come in different types, like earthen, masonry and arch dams.
- WhyThe type depends on the place and the material available.
- HowEarthen dams use soil, masonry dams use stone, and arch dams use a curved shape.
- ExampleHirakud is earthen, Nagarjuna Sagar is masonry, and Idukki is an arch dam.
- So whatEach type suits a different situation.
- WhatThe water stored behind a dam is called a reservoir.
- WhyExams sometimes ask what is common to certain place names.
- HowPlaces like Aliyar, Isapur and Kangsabati are all water reservoirs.
- ExampleUPSC asked exactly this in 2019, and the answer was water reservoirs.
- So whatKnow the names of important reservoirs.
- WhatA dam is a solid wall across a river, so boats and ships cannot pass through it.
- WhyThis matters because rivers are often used as water roads to carry goods and people.
- HowThe dam splits the river into two parts, so a boat must stop at the wall and transfer its load, or the route is cut completely.
- ImpactThe dam can also lower the water level downstream, making the river too shallow for big boats to travel.
- ExampleThink of a dam like a locked gate across a highway, so every vehicle has to stop and unload there.
- WhatRivers carry fine soil called silt, and a dam stops it from moving downstream.
- WhyOver time, silt settles and piles up at the bottom of the reservoir behind the dam.
- HowAs silt builds, the reservoir fills up and can hold less water, so the dam produces less power and supplies less water for farming.
- ImpactDownstream, the river loses the fertile silt that once naturally fertilised the farmlands.
- ExampleThink of a glass slowly filling with sand, the sand takes up space, so less water fits each year.
PYQ / Exam Angle
The Bhakra Nangal Project
- QuestionCDS and other competitive exams ask which river feeds the Bhakra Nangal Project’s canal system.
- WhyThe Bhakra Nangal Project gets its water from the Sutlej (Satluj) River.
- HowThe dam on the Sutlej stores water and sends it into canals.
- ExampleThe Sutlej is a tributary of the Indus, and it powers this famous dam.
- LinkSource: CDS (I) 2021, General Knowledge (see this question).
Current Affairs / So What
Dams and Floods
- WhatDams can also help control floods by holding back extra water.
- WhyThis is important because heavy rain can cause rivers to overflow.
- HowA dam lets out only a safe amount of water at a time.
- ExampleThe Hirakud Dam helps protect Odisha from the Mahanadi’s floods.
- So whatDams protect both life and crops.
Dams Today
- WhatIndia keeps building and managing dams for water and power.
- WhyThey support growing cities, farms and energy needs.
- HowNewer dams aim to store water and make clean electricity.
- ExampleDams like Sardar Sarovar supply water to millions of people.
- So whatDams remain central to India’s development.
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