What is the Mettur Dam?

Mettur Dam (Stanley Reservoir) is built across the Cauvery River in Salem district, Tamil Nadu. It was completed in 1934 (during British era, under Governor Montagu Cholmeley Butler). It is one of the largest dams in India. Water is released every year on June 12 (traditional date) for Cauvery Delta irrigation. It supplies water to Erode, Salem, Tiruchirapalli, and Thanjavur districts.

What is the Cauvery water dispute?

The Cauvery water dispute is between Karnataka (upper riparian state — controls Mettur's inflows) and Tamil Nadu (lower riparian state — depends on Cauvery for agriculture). The dispute is over sharing of Cauvery waters. The Cauvery Water Disputes Tribunal (1990) gave its final award in 2007. The Supreme Court modified it in 2018, and the Cauvery Water Management Authority (CWMA) was set up to monitor releases.

Which is the longest river in India?

The Ganga (Ganges) is the longest river entirely within India at approximately 2525 km. The Indus is longer overall (3180 km) but most of it flows through Pakistan. The Godavari (1465 km) is the longest peninsular river and is called 'Dakshin Ganga' (Ganga of the South). The Cauvery (805 km) is entirely within South India.

Rivers, Dams and Reservoirs — TNPSC Group II/IIA Geography

Overview

Rivers are the lifelines of India — providing water for irrigation, drinking, and hydroelectricity. For TNPSC Group 2/2A, focus on the classification of rivers (Himalayan vs Peninsular), major rivers and their tributaries, key dams, and especially Tamil Nadu's river systems and reservoirs.

Classification of Indian Rivers

Himalayan Rivers vs Peninsular Rivers

Feature	Himalayan Rivers	Peninsular Rivers
Source	Glaciers + monsoon rainfall	Rainfall only (seasonal)
Flow	Perennial (year-round)	Seasonal (may dry in summer)
Age	Young rivers; young mountains	Ancient; old rocks
Course	Long; flow from north	Shorter; mostly flow east
Valleys	Deep gorges in mountains; flat plains	Shallow, broad valleys
Gradient	High gradient in mountains	Low gradient
Examples	Ganga, Yamuna, Indus, Brahmaputra, Sutlej	Godavari, Krishna, Cauvery, Mahanadi

Major Himalayan Rivers

Indus River System

River	Origin	Length	Key Facts
Indus (Sindhu)	Tibet (near Mansarovar)	3180 km	Mostly in Pakistan; Indus Valley Civilisation
Sutlej	Tibet	1450 km	Bhakra-Nangal Dam
Beas	Beas Kund, Kullu	470 km	Pong Dam
Ravi	Himachal Pradesh	720 km	Thein Dam
Jhelum	Kashmir	725 km	Dal Lake; flows to Pakistan
Chenab	Himachal Pradesh	960 km	Salal Dam

Ganga River System

River	Origin	Length	Key Facts
Ganga	Gangotri Glacier, Uttarakhand	2525 km	Longest river in India; joins Brahmaputra at Sundarbans (delta)
Yamuna	Yamunotri Glacier, Uttarakhand	1376 km	Tributary of Ganga; joins at Prayagraj
Ghaghra	Tibet	1080 km	Right bank tributary
Gomti	UP	960 km	Lucknow on its banks
Son	Amarkantak, MP	784 km	Right bank tributary
Brahmaputra	Tibet (Tsangpo)	2900 km total	Enters India through Arunachal; forms largest delta

Major Peninsular Rivers

East-flowing Rivers (flow to Bay of Bengal)

River	Origin	Length	Key States
Godavari	Trimbakeshwar, Maharashtra	1465 km	Maharashtra, AP, Telangana (Dakshin Ganga)
Krishna	Mahabaleshwar, Maharashtra	1400 km	Maharashtra, Karnataka, Andhra Pradesh
Cauvery (Kaveri)	Talakaveri, Kodagu	805 km	Karnataka, Tamil Nadu
Mahanadi	Chhattisgarh	858 km	Chhattisgarh, Odisha
Pennar	Karnataka	597 km	Karnataka, Andhra Pradesh

West-flowing Peninsular Rivers (flow to Arabian Sea)

River	Origin	Length	Key Facts
Narmada	Amarkantak, MP	1312 km	Flows in Narmada rift valley; Sardar Sarovar Dam
Tapi (Tapti)	Betul, MP	724 km	Parallel to Narmada
Mahe	Kerala	Small	Flows west in Kerala

Tamil Nadu Rivers

River	Origin	Enters TN from	Districts
Cauvery (Kaveri)	Kodagu, Karnataka	Western Ghats	Erode, Salem, Tiruchirapalli, Thanjavur, Tiruvarur, Nagapattinam
Vaigai	Periyar hills	Madurai	Madurai, Dindigul, Sivagangai, Ramanathapuram
Tamirabarani	Agasthyamalai	Near Tirunelveli	Tirunelveli, Thoothukudi
Palar	Karnataka	Vellore	Vellore, Ranipet, Kanchipuram, Chennai
Cheyyar	Salem	—	Salem, Tiruvannamalai
Ponnaiyar	Karnataka	—	Tiruvannamalai, Cuddalore, Villupuram

Major Dams and Reservoirs

National Dams

Dam	River	State	Significance
Sardar Sarovar	Narmada	Gujarat	Largest dam in India by concrete volume; controversial
Bhakra-Nangal	Sutlej	Punjab/HP	Largest multipurpose dam in India; Gobind Sagar reservoir
Tehri Dam	Bhagirathi	Uttarakhand	Tallest dam in India (260m)
Hirakud	Mahanadi	Odisha	Longest dam in India (4.8 km)
Nagarjunasagar	Krishna	Telangana	Large masonry dam
Srisailam	Krishna	Telangana/AP	Second largest reservoir
Tungabhadra	Tungabhadra	Karnataka	Tungabhadra project

Tamil Nadu's Major Dams and Reservoirs

Dam/Reservoir	River	District	Key Facts
Mettur Dam (Stanley Reservoir)	Cauvery	Salem	Completed 1934; 60m high; large irrigation project
Vaigai Dam	Vaigai	Dindigul (Madurai border)	1959; irrigates Madurai, Sivagangai, Ramanathapuram
Papanasam Dam (Servalar)	Tamirabarani	Tirunelveli	Hydroelectricity + irrigation
Krishnagiri Reservoir	Thenpennai	Krishnagiri	—
Poondi Reservoir (Pulicat Lake system)	Kosasthalaiyar	Tiruvallur	Water supply to Chennai
Veeranam Lake	—	Cuddalore	Ancient tank; water supply to Chennai
Red Hills Lake	—	Chennai	Chennai water supply
Chembarambakkam	Adyar	Kancheepuram	Chennai water supply
Bhavanisagar Dam	Bhavani	Erode	Irrigation and hydroelectricity

Mettur Dam — Key Details for TNPSC

Aspect	Details
Official name	Stanley Reservoir
River	Cauvery
District	Salem (Mettur)
Completion	1934 (British era)
Height	60m (197 feet)
Purpose	Irrigation, water supply, hydroelectricity
Water release	Traditionally June 12 for Cauvery delta irrigation
Districts irrigated	Erode, Salem, Namakkal, Tiruchirapalli, Thanjavur, Tiruvarur, Nagapattinam

Cauvery River — Most Important for Tamil Nadu TNPSC

Course of Cauvery

Segment	Details
Origin	Talakaveri, Kodagu (Coorg), Karnataka; 1341m elevation
Length	805 km
States	Karnataka → Tamil Nadu → Puducherry
Major tributaries	Hemavathi, Kabini, Bhavani, Amaravati, Noyyal, Kollidam
Delta	Thanjavur district — "Granary of Tamil Nadu"
Mouth	Enters Bay of Bengal at Poompuhar (Kaveripattinam), Nagapattinam

Cauvery Tributaries in Tamil Nadu

Tributary	Joins Cauvery
Bhavani	Near Bhavani town, Erode
Noyyal	Near Tiruchirapalli
Amaravati	Near Karur
Kollidam (Coleroon)	Major distributary — splits near Srirangam

Key Facts for TNPSC Group II/IIA

Ganga (2525 km): Longest river entirely in India; originates at Gangotri Glacier
Godavari (1465 km): Longest peninsular river; "Dakshin Ganga"
Cauvery (805 km): Flows through Karnataka and Tamil Nadu; life of Tamil Nadu's delta
Mettur Dam: Built 1934 on Cauvery; Salem district; water released June 12 traditionally
Vaigai Dam: 1959; irrigates Madurai, Sivagangai, Ramanathapuram districts
Bhakra-Nangal: On Sutlej; largest multipurpose dam in India; Gobind Sagar reservoir
Hirakud (Odisha): Longest dam in India (4.8 km)
Tehri Dam (Uttarakhand): Tallest dam in India (260m)
Cauvery Water Dispute: Karnataka vs Tamil Nadu; Tribunal 1990; CWMA formed 2018
Tamirabarani: Cleanest river in India; flows through Tirunelveli; perennial

Previous Year MCQ Patterns

Q: The Mettur Dam is built across which river? a) Vaigai b) Tamirabarani c) Cauvery d) Palar

Answerc) Cauvery — Mettur Dam (officially Stanley Reservoir) is built across the Cauvery River in Mettur, Salem district, Tamil Nadu. Completed in 1934 during British rule, it is one of India's largest dams and irrigates the Cauvery delta. Water is traditionally released on June 12 for Samba paddy cultivation.

Q: Which is the longest peninsular river in India? a) Krishna b) Cauvery c) Godavari d) Mahanadi

Answerc) Godavari — The Godavari (1465 km) is the longest peninsular river in India. It originates at Trimbakeshwar in Nashik, Maharashtra, and flows through Telangana and Andhra Pradesh before emptying into the Bay of Bengal. It is called "Dakshin Ganga" (Ganga of the South) for its large size and cultural significance.

Q: Which dam is known as the "longest dam in India"? a) Bhakra-Nangal Dam b) Hirakud Dam c) Tehri Dam d) Sardar Sarovar Dam

Answerb) Hirakud Dam — Hirakud Dam on the Mahanadi River in Odisha is the longest dam in India at approximately 4.8 km (including dykes: 25.8 km). It was the first large multipurpose dam built after independence, completed in 1957. Tehri Dam in Uttarakhand is the tallest (260m).

Frequently Asked Questions

Himalayan Rivers: Fed by glaciers and monsoon; perennial (flow throughout the year); longer; form large deltas; have high potential for irrigation and hydroelectricity. Examples: Ganga, Yamuna, Indus, Brahmaputra. Peninsular Rivers: Fed only by rainfall; seasonal (may dry up in summer); shorter; older rocks; flow east to Bay of Bengal. Examples: Godavari, Krishna, Cauvery, Mahanadi.