The Teesta River

The Teesta is a Himalayan river that rises in the far north of Sikkim. It is fed by glaciers and snowfields. It starts high and falls steeply to the plains.

What is the source of the Teesta?

The Sikkim State of Environment Report says the Teesta starts as the Chhombo Chhu. It comes from a glacial lake called Khangchung Chho, at about 5,280 metres. The lake lies below the Teesta Khangse glacier. That glacier comes down from Pauhunri peak, which is 7,056 metres high.

Many writers also name Chho Lhamo, along with the Teesta Khangse glacier, as the source. One Bangladeshi river survey puts a source lake at about 5,330 metres. Sources differ by a few dozen metres. For exams, remember “a glacial lake in North Sikkim, at about 5,300 metres”.

Does the Teesta share a source with the Brahmaputra?

No. NCERT says the Brahmaputra begins in the Chemayungdung glacier of the Kailash range. That glacier is near Mansarovar lake in Tibet. The Teesta begins in Sikkim, at a different source.

The two rivers meet only far downstream, in Bangladesh.

Where do the Lachen and Lachung streams meet?

The upper Teesta is fed by two mountain streams, the Lachen Chu and the Lachung Chu. They meet at Chungthang in North Sikkim. Chungthang later became the site of the Teesta III dam.

Which state is the Teesta’s home state?

The Teesta system drains Sikkim. Its Sikkim catchment is 6,930 sq. km. Sikkim became India’s 22nd state on 16 May 1975. A referendum had backed merger with India, and the rule of the Chogyal monarchy ended.

The Constitution (Thirty-sixth Amendment) Act, 1975, made Sikkim a full state. It also added Article 371F, which gives Sikkim special provisions.

How does it flow through Sikkim?

After Chungthang the river runs south through Mangan and Singtam. At Rangpo it receives the Rangpo Chhu. Further downstream it forms the boundary between Sikkim and West Bengal.

The Sikkim report says the river leaves the hills at Sevoke, near Siliguri. It travels about 40 km from Melli before it reaches the plains. On the plains it fans out and is sometimes 4 to 5 km wide.

How long is the Teesta?

The usual figure is about 414 km. The MoEF basin study and an ICIMOD paper both give it. A Singapore study splits it into 151 km in Sikkim, 142 km along the border and in West Bengal, and 121 km in Bangladesh. Some writings say 315 km. Use 414 km.

How big is its catchment?

The Sikkim report gives a catchment of 12,159 sq. km.

• Sikkim: 6,930 sq. km.
• West Bengal: 3,225 sq. km (1,121 in the hills and 2,104 on the plains).
• Bangladesh: 2,004 sq. km.

About 30 million people live in the basin. Most live in north-west Bangladesh and in West Bengal.

Which rivers join the Teesta?

The Sikkim report lists the main tributaries by bank:

• Left bank: Lachung Chhu, Chakung Chhu, Dik Chhu, Rani Khola and Rangpo Chhu.
• Right bank: Zemu Chhu, Rangyong (Talung) Chhu and the Rangit (Rangeet) river.

The Rangeet is a genuine tributary of the Teesta. On the plains, the Leesh, Geesh, Chel and Neora join from the north-east. The Karala joins from the north-west.

What else is the Teesta hill country known for?

The hills of Darjeeling drain towards the Teesta. Darjeeling tea grows there. It is called the “champagne of teas”. It was the first product registered under India’s Geographical Indications Act, 1999. The registry shows the certificate was issued on 29 October 2004.

A GI tag protects the product’s name and its place of origin.

Does the Teesta reach the Bay of Bengal directly?

No. NCERT says the Teesta joins the Brahmaputra on its right bank in Bangladesh. From there the river is known as the Jamuna. The Jamuna then merges with the Padma, which falls into the Bay of Bengal.

The Bangladeshi river survey puts the meeting in Sundarganj, in Gaibandha district. The Sikkim report says it is at about 23 metres above sea level.

Which way did the Teesta flow before 1787?

Before 1787 the Teesta split near Jalpaiguri into three channels. They were the Karatoya to the east, the Atrai in the middle and the Punarbhaba to the west. Together they were called the Trisrota.

In the great flood of 1787 the Teesta changed its eastern course. It turned south-east and joined the Brahmaputra. Banglapedia dates the Brahmaputra’s move to its present Jamuna course to the same year.

What does a practice question on the Teesta test?

A practice question on the Teesta gives three statements. The first said the Teesta has the same source as the Brahmaputra. The second said the Rangeet is a Teesta tributary that rises in Sikkim. The third said the Teesta flows into the Bay of Bengal on the India-Bangladesh border.

Only the second is correct. The Rangeet rises in the Talung glacier area of West Sikkim. It joins the Teesta near Melli. The answer is “2 only”.

Where is the barrage?

The main barrage stands across the Teesta at Gajoldoba, also spelled Gozaldoba. It is the heart of the Teesta Barrage Project. The project also has barrages on the Mahananda and the Dauk rivers.

Why was it planned?

The West Bengal irrigation department says the aim was irrigation, hydropower, navigation and flood moderation. ORF writes that the project was conceived after the 1968 floods in Jalpaiguri. Work began in the mid-1970s.

What was the 1968 flood?

Heavy rain fell over the Sikkim and Darjeeling hills from 2 to 5 October 1968. A newspaper report says about a thousand people died. Houses and bridges were washed away.

What is the Dalia barrage?

The plan was for two barrages about 100 km apart. One would be at Gajoldoba in India and the other at Dalia in Bangladesh. Together they were meant to irrigate about 16 lakh hectares. About 9.2 lakh hectares were in West Bengal.

Bangladesh says that the Gajoldoba barrage draws water in the dry season without sharing it fairly.

What is the Teesta III dam?

Teesta III is at Chungthang. It is Sikkim’s biggest hydropower project, with a capacity of 1,200 MW. The dam is about 60 metres high. It was built by Teesta Urja Limited.

What are Teesta V and Teesta VI?

Teesta V is run by NHPC. It has a capacity of 510 MW. Teesta VI is an NHPC project of 500 MW. It was still under construction in 2023.

What happened to them in 2023?

The flood of October 2023 destroyed the Teesta III dam. NHPC said Teesta V and Teesta VI suffered catastrophic damage. The Power Ministry said it would assess the damage.

Hydropower dams in a glacier valley carry a special risk. A sudden flood from a lake can overtop or break them.

What is a GLOF?

A GLOF is a glacial lake outburst flood. A lake of meltwater sits behind a wall of rock and ice, called a moraine. If the wall breaks, the water rushes downstream.

What happened on the night of 3-4 October 2023?

South Lhonak Lake lies in North Sikkim, at about 5,200 metres. It had grown for years as its glacier melted. Around midnight on 3 to 4 October 2023, the lake burst. A wall of water then hit the Teesta valley.

The Teesta III dam at Chungthang was washed away in minutes. The flood also swept away bridges. Army personnel were among the missing.

What caused the flood?

Early reports blamed a cloudburst over the lake. A later study by ICIMOD points to a different trigger. A large part of the lateral moraine collapsed into the lake. This sent a wave about 20 metres high that eroded the front moraine wall. About 50 million cubic metres of water was released.

Sources disagree on the exact trigger. Learn it as a moraine collapse.

How many people died?

Counts changed over time. Sikkim’s disaster authority reported 42 dead and 77 missing on 1 November 2023. A later study counts 55 casualties. Do not memorise the toll. Remember that dozens died.

What is the NGRMP?

In July 2024 a High-Level Committee approved Rs 150 crore for the National GLOF Risk Mitigation Project (NGRMP). Home Minister Amit Shah chaired that committee.

Which states are covered?

The project covers four Himalayan states. They are Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh.

The Rs 150 crore is shared out as follows:

• Arunachal Pradesh: Rs 45 crore.
• Sikkim: Rs 40 crore.
• Himachal Pradesh: Rs 35 crore.
• Uttarakhand: Rs 30 crore.

What does the money buy?

The project aims to reduce GLOF risk. Its first component is a hazard assessment with a lake inventory. The second is monitoring and early warning. The third is mitigation work. The Centre pays Rs 135 crore from the National Disaster Mitigation Fund. The states pay Rs 15 crore.

Why does Bangladesh want the Teesta’s water?

About 71 per cent of the Teesta basin’s people live in north-west Bangladesh. In the dry season the river is low. Both countries need the water for farms.

What happened in 2011?

In September 2011 a deal was nearly ready during Manmohan Singh’s visit to Dhaka. West Bengal’s chief minister Mamata Banerjee objected. She said north Bengal would face a summer water crisis. The Centre put the deal on hold.

Reports give different sharing figures for the 2011 draft. Remember the fact, not the numbers. The deal was not signed.

Why does the state matter?

Water is a State List subject in the Constitution. The Union said it would do nothing without the states’ consent. So West Bengal’s view mattered.

Where does it stand now?

No treaty has been signed. News reports from 2026 say the political change in West Bengal has reopened the door to a deal. The 1996 Ganga Water Treaty is also due to expire in December 2026.

Why does China matter?

Bangladesh has discussed a Chinese-backed Teesta River Comprehensive Management and Restoration Project. A 2020 report called it a scheme worth about US$1 billion. India watches it because the Teesta lies near the Siliguri Corridor.