The large-dam debate and dam safety

Detail

1. Why dams matter, and why they are questioned

• Multipurpose project means one dam that does many jobs: irrigation, hydropower, flood control, drinking water, fishing and inland navigation. Nehru called these dams the "temples of modern India".
• India's dam-building is very old. The Kallanai (Grand Anicut) on the Kaveri in Tamil Nadu is India's oldest dam and has worked for nearly 2,000 years [2].
• From the 1980s, people began to ask whether large dams cost more than they give. NCERT asks students to think about this too. It says large-scale displacement and loss of livelihood are "not an argument in favour" of dams.

2. Criticism of large dams: what goes wrong with the river

Criticism of large dams means the list of harms that big reservoirs do to rivers, land and people.

• Changed natural flow and sediment starvation
• A dam controls the river, so the natural rise and fall of water stops.
• Silt (fine soil carried by the river) settles in the still water of the reservoir. This is called sedimentation.

• Below the dam, the river carries little silt. Its bed becomes rocky, so fish and other water life lose their habitat.

• Fragmentation

• A dam cuts a river into separate pieces.

• Fish that swim upstream to lay eggs (spawning migration) can no longer reach their breeding grounds.

• Submergence

• The reservoir drowns forests, farmland and soil.

• The drowned plants rot under water.

• Floodplains lose fertility

• Floods used to spread fresh silt over the floodplain (the flat land beside a river that floods in the rainy season).
• Once a dam stops this, the soil gets poorer and the land degrades.

3. The paradox: dams that fail at flood control

• Cause → process → result

• Silt fills the reservoir → it can store less flood water → in very heavy rain the dam has to release water suddenly → people downstream are flooded.

• NCERT notes that many dams built for flood control have triggered floods during extreme rain.

4. Earthquakes, disease and salty soil

• Reservoir-induced seismicity means earthquakes set off by filling a reservoir.
• The huge weight of the water presses on the rocks below.
• Water seeps into cracks (faults) and makes them slip more easily.

• Result: an earthquake. Koyna (Koyna river, Satara district, Maharashtra) had a major earthquake on 11 December 1967. It is the best-known Indian example.

• Water-borne diseases and pests: still reservoir and canal water helps mosquitoes and other disease carriers breed.

• Salinisation means salt building up in the soil.

• Cheap canal water → farmers switch to thirsty cash crops such as sugarcane and paddy → too much water is used → the water table rises and salts are pulled up to the surface → the soil turns salty and loses fertility.

• Social cost: dams displace large numbers of people, often tribal people and the rural poor, and destroy their livelihoods.

5. Social movements against dams

Case	River and state	Main issue	Outcome
Sardar Sarovar	Narmada; dam at Navagam, Gujarat (submergence also in Madhya Pradesh and Maharashtra)	Displacement and poor rehabilitation	Narmada Bachao Andolan (Medha Patkar, Baba Amte) went to court. In Narmada Bachao Andolan v. Union of India (2000) the Supreme Court allowed building to go on, on condition that people were resettled
Tehri	Bhagirathi, Uttarakhand	Very tall (about 260 m, India's highest dam), in a seismic zone, and it displaced people	Opposed by Sunderlal Bahuguna. Built anyway
Silent Valley	Kunthipuzha, Palakkad, Kerala	Would have drowned one of the last untouched tropical evergreen forests (home of the lion-tailed macaque)	Hydro project dropped in the early 1980s. The area became a national park in 1984

• World Commission on Dams (2000): this global commission reviewed large dams and asked for fair options assessment, consent of affected people and sharing of benefits. Its report became a world benchmark.

6. The counter-case: what dams give

• Bhakra (Sutlej, Himachal Pradesh) and Hirakud (Mahanadi, Odisha) show the gains:
• Drought-proofing: stored monsoon water is used in the dry season. Bhakra water helped drive the Green Revolution in Punjab, Haryana and Rajasthan.
• Hydropower: clean, firm electricity.

• Flood moderation: Hirakud reduced floods in the Mahanadi delta.

• India also needs stored water because about three-fourths of its rain falls in only about four monsoon months.

7. Synthesis: a balanced approach

• Options assessment: first check whether smaller options (check dams, tanks, rainwater harvesting, better irrigation efficiency) can do the job.
• Environmental flows (e-flows): always release enough water downstream to keep the river alive.
• Cumulative basin impact studies: judge all the dams in one river basin together, not one by one. This matters most for Himalayan cascades (many dams one after another on the same river). Links: biodiversity conservation; natural hazards and disasters.

8. Dam safety: India's dam stock

• India ranks 3rd in the world for large dams, after China and the USA, with 6,628 specified dams (2026). Of these, 6,545 are operational and 83 are under construction [2]. (Earlier estimates put the number at about 5,700.)
• Their gross storage is about 330 billion cubic metres [2].
• Age (2026) [2]:
• About 26% (1,681 dams) are more than 50 years old. This includes 291 that are more than 100 years old.

• About 42% are 25–50 years old.

• Ownership (2026) [2]:

• About 98.5% (6,448) are owned by state governments.

• Central PSUs own 49, private bodies own 36 and the Central Government owns 12.

• States with the most specified dams (2026), in order: Maharashtra, then Madhya Pradesh, Gujarat, Chhattisgarh, Rajasthan, Karnataka and Odisha [2].

9. Dam Safety Act 2021

• Dam Safety Act 2021 is India's first national law on the safety of dams. It came into force on 30 December 2021 [2].
• Specified dam means a dam more than 15 m high, or a dam 10–15 m high that meets certain technical conditions [2].
• Duties of dam owners [2]:
• regular inspections and instruments to monitor the dam
• full safety reviews and risk assessments
• inflow forecasting and early warning systems

• an Operation & Maintenance Manual and Emergency Action Plans (EAPs) (plans for warning and evacuating people if a dam fails)

• Four-tier institutional set-up [2]:

Level	Body	Role
National	National Committee on Dam Safety (NCDS)	Apex body. Makes policy
National	National Dam Safety Authority (NDSA)	Regulator. Carries out NCDS policy and gives technical help to the states
State	State Committee on Dam Safety (SCDS)	Watches over dam safety in the state
State	State Dam Safety Organisation (SDSO)	Handles surveillance, inspection and compliance. All 31 dam-owning states have set one up

• Progress under the Act (2026) [2]:
• All 6,628 specified dams are registered on DHARMA (Dam Health and Rehabilitation Monitoring Application).
• About 13,000 inspections are done every year.
• Rapid Risk Screening is complete for 5,553 dams.
• 20 regulations have been notified.
• A National Centre for Earthquake Safety of Dams has been set up at MNIT Jaipur.

10. DRIP: repairing old dams

• DRIP (Dam Rehabilitation and Improvement Project) is run by the Central Water Commission to repair dams and make them work better.

Phase	Period	Coverage	Money
Phase I	April 2012 – March 2021	223 dams in 7 states: Jharkhand, Karnataka, Kerala, Madhya Pradesh, Odisha, Tamil Nadu and Uttarakhand	₹2,567 crore; World Bank loan of US$309 million [2][3]
Phase II and III	10 years in two six-year phases that overlap by two years (April 2021 – March 2031)	736 dams in 19 states, plus central agencies such as the Bhakra Beas Management Board and the Damodar Valley Corporation	₹10,211 crore. Loans of US$1 billion (₹7,000 crore) from the World Bank and the Asian Infrastructure Investment Bank (AIIB) [3]

11. The Periyar Diversion Scheme

• An inter-basin transfer means moving water from one river basin to another. The Periyar Diversion Scheme (1895) is NCERT's example.
• Spatial anchors
• The Periyar rises in the Western Ghats of Kerala. It flows west to the Arabian Sea near Kochi and is Kerala's longest river.

• The Vaigai rises in the hills of Tamil Nadu. It flows east to the Palk Strait near Ramanathapuram.

• How it works

• The Mullaperiyar dam stores Periyar water → a tunnel through the Western Ghats carries it east → the water enters the Vaigai basin → it irrigates the dry, rain-shadow Madurai region (Theni, Madurai, Dindigul, Sivaganga and Ramanathapuram).

• The reservoir lies inside the Periyar Tiger Reserve (Thekkady).

12. Mullaperiyar dam: safety meets federalism

• Mullaperiyar dam: a masonry gravity dam (built of stone and lime; it holds back water by its own weight). It was completed in 1895 by John Pennycuick. It stands in Idukki district, Kerala, where the Mullayar meets the Periyar.
• Lease: signed in 1886 between the Maharaja of Travancore and the Madras Presidency, for 999 years. The dam is in Kerala, but Tamil Nadu operates it and uses its water.
• Kerala's case: the dam is very old and stands in an earthquake-prone area. Lakhs of people live downstream. Kerala wants a new dam.
• Tamil Nadu's case: the dam has been strengthened and is safe. Southern Tamil Nadu depends on its water.
• Court timeline
• 2006: the Supreme Court allowed the water level to be raised to 142 ft. Kerala then passed a law that capped it at 136 ft.
• 2014: the Supreme Court struck down Kerala's law, allowed 142 ft again and set up a Supervisory Committee.

• 8 April 2022: the Court ordered the Supervisory Committee to use all the powers of the NDSA until the NDSA starts working fully. It added one technical expert each from Kerala and Tamil Nadu and ordered a fresh safety review under the 2021 Act. The Chief Secretaries of both states are personally responsible for carrying out the Committee's orders [4].

• Why it matters for exams: one case brings together dam safety, federalism (Centre–state and state–state relations) and inter-basin transfer.

Prelims Hooks

• Koyna earthquake (1967), Maharashtra is the classic Indian case of reservoir-induced seismicity.
• Tehri is on the Bhagirathi (Uttarakhand), about 260 m high, and was opposed by Sunderlal Bahuguna. Sardar Sarovar is on the Narmada (Gujarat) and was opposed by Medha Patkar and Baba Amte.
• Silent Valley (Kerala) is a hydro project that was dropped to save the forest. It became a national park in 1984.
• Dam Safety Act 2021 came into force on 30 December 2021. A specified dam is more than 15 m high, or 10–15 m high if it meets set criteria. NCDS makes policy; NDSA is the regulator [2].
• India ranks 3rd in large dams (after China and the USA), with 6,628 specified dams. Maharashtra has the most [2].
• About 26% of India's dams are more than 50 years old, and 291 are more than 100 years old (2026) [2].
• DRIP Phase II and III cover 736 dams and are funded by the World Bank and AIIB [3].
• Periyar Diversion Scheme: water moves from the west-flowing Periyar (Kerala) into the east-flowing Vaigai (Tamil Nadu). Mullaperiyar is in Idukki, Kerala but is operated by Tamil Nadu under a 999-year lease (1886).
• Trap: India's oldest working dam is the Kallanai (Grand Anicut) on the Kaveri, not Mullaperiyar [2].

Mains Points

• Costs and benefits of large dams (GS-III): dams cause sediment starvation, broken rivers, induced earthquakes, salty soils and displacement (Sardar Sarovar, Tehri). They also give drought-proofing, hydropower and flood moderation (Bhakra, Hirakud). The answer lies in options assessment, environmental flows, cumulative basin studies and fair resettlement, in line with the World Commission on Dams (2000).
• Ageing dams are a disaster risk (GS-III): 1,681 dams are more than 50 years old [2], and silt and climate-driven extreme rain add to the danger. Responses: the Dam Safety Act 2021 (four-tier bodies, Emergency Action Plans, DHARMA, risk screening) and repairs under DRIP [2][3].
• Federalism and inter-basin transfer (GS-I/II): in Mullaperiyar, a dam in one state serves another state under a colonial lease. It shows how disputes over safety and water sharing end up in the Supreme Court, and why a central regulator such as the NDSA is needed [4].
• Lessons for Himalayan cascades: seismic zones, fragile slopes and dams placed one after another on the same river need cumulative impact studies before new projects are approved.