Diving into dams: A guide to India’s most important water structures

Info Nuggets

Ravneet Kaur

TNS

Chandigarh, Updated At : 08:04 PM Sep 08, 2025 IST

Sardar sarovar dam, Narmada district, Gujarat

Important dams in India

1. Highest dam in India

• Tehri Dam, Uttarakhand

Height: 260.5 m (Tallest in India, among the tallest in the world)

River: Bhagirathi (tributary of Ganga)

Purpose: Hydropower (1,000+ MW), irrigation, drinking water

2. Longest dam in India

• Hirakud Dam, Odisha

Length: Rs 25.8 km (world’s longest earthen dam)

River: Mahanadi

Purpose: Flood control, irrigation, hydropower

3. Highest gravity dam in India

• Bhakra Dam, Himachal Pradesh-Punjab

Length: Rs 518 m (across the river)

River: Sutlej river

Purpose: Hydropower, irrigation, flood control

Reservoir: Govind Sagar Lake

4. Largest reservoir in India

• Indira Sagar Dam, Madhya Pradesh

Reservoir capacity: 12.2 billion cubic meters

River: Narmada

5. Oldest major dam

• Kallanai (Grand Anicut), Tamil Nadu

Built in 2nd century CE by Chola king Karikalan

River: Kaveri

Still functional — irrigation purpose

6. Smallest dam (by scale, not officially defined)

• Many local check dams and anicuts exist across India, especially in arid regions like Rajasthan.

Important rivers of North India & their dams

Ganga Basin

• Bhagirathi-Tehri Dam (Uttarakhand)

• Ramganga Dam (Kalagarh, Uttarakhand)

• Bansagar Dam (Son River, Madhya Pradesh)

Yamuna Basin

• Hathnikund Barrage (Haryana)

• Lakhwar-Vyasi Project (under construction, Uttarakhand)

Sutlej Basin

• Bhakra Nangal Dam (Himachal Pradesh-Punjab)

• Bhakra: 226 m high, India’s second-highest dam

• Critical for irrigation in Punjab, Haryana, Rajasthan

Beas Basin

• Pandoh Dam (Himachal Pradesh)

• Pong Dam (Maharana Pratap Sagar) (Himachal Pradesh)

Chenab Basin

• Salal Dam (J&K)

• Baglihar Dam (J&K)

• Dulhasti Dam (J&K)

Ravi Basin

• Ranjit Sagar Dam (Thein Dam) – Punjab–J&K border

India-Pak dams & Indus Waters Treaty significance

The Indus Waters Treaty (1960) gives:

• Eastern rivers (Ravi, Beas, Sutlej) – allocated to India

• Western rivers (Indus, Jhelum, Chenab) – allocated to Pakistan, but India can use them for non-consumptive purposes (hydropower, navigation, storage limits apply).

Key Indian projects that affect Pakistan

• Baglihar Dam (Chenab, J&K) → Pakistan objected under IWT

• Kishanganga Project (Jhelum tributary, J&K) → International arbitration dispute, India allowed to divert some water

• Ratle Hydroelectric Project (Chenab) → Another point of contention

What is a ‘cusec’ of water?

• Cusec = Cubic feet per second

• 1 cusec = 1 cubic foot of water flowing per second

• In litres:

1 cubic foot = 28.317 litres

So, 1 cusec = 28.3 litres/second

• In cubic meters:

1 cubic meter = 35.3 cubic feet

1 cusec ≈ 0.028 cubic meters/second

If 1,000 cusecs of water is released, it equals 28,300 litres per second (or about 28.3 kilolitres/sec).

Over a day: Rs 2.45 crore litres (24.5 million litres).

This helps visualise flood releases from dams — when you read “50,000 cusecs released,” that’s an enormous flood discharge.

Quick UPSC takeaways

• Cusec = unit of discharge (28.3 litres/sec).

• Tehri = highest, Hirakud = longest, Indira Sagar = largest reservoir.

• North India’s water system is tied to Indus Basin rivers.

• Indus Waters Treaty (1960) is a must-know for international relations & geography.

• Dams = multiple functions → irrigation, flood control, drinking water, hydropower.