Brahmaputra River has been making headlines lately, not just for the usual flooding issues but also due to a tragic boat accident in September 2021 that resulted in the loss of several lives. This river is a crucial system, boasting one of the largest drainage capacities in India after the Ganga. It plays a vital role as a lifeline for the northeastern states nestled in the foothills of the eastern Himalayas. The river shapes fertile floodplains, influencing the region’s geography, ecology, and cultural landscape.

About Brahmaputra River

• Brahmaputra River originates in the great glacier mass north of Kailash ranges of the Himalayas (elevation 5,150 m) & south of a lake called ‘Konggyu Tsho’.
• It is only next to Amazon with a specific yield of 85 ha m / sq km in comparison to 87 ha m /sq km of the latter.
• Brahmaputra traverses a distance of 2,900 km through four countries – Tibet (China), Bhutan, India and Bangladesh before entering the Bay of Bengal.
• The source of this river lies in the Kanglung Kang Glacier near the Kailash range of the Himalayas located in the south-western part of the Tibetan plateau at an elevation of 5,300 m, near Konggyu Tso Lake Here, the river is called Tamchok Khambab Kangri.
• Many snow-fed streams join the river from the passes at about 60 km southeast of Mansarovar Lake.
• It has a catchment area of 580,000 sq. km, an average annual discharge of 19,820 cumec, an average annual sediment load of 735 million metric tonnes, and a specific flood discharge of 0.149 cumec/ sq. km. The catchment area of the river falls in four countries.

Salient Features of Brahmaputra River

• The river system is on the landmass enclosed on the north by the Himalayas, on the east by the Patkai range of hills running along the Assam-Burma border, on the south by the Assam range of hills and on the west by the Himalayas and the ridge.
• The Brahmaputra river system regions witness one of the heaviest rainfall patterns in the world, particularly the portions in Assam, and are prone to annual floods and riverbank erosion.
• Parts of the Himalayan Mountains region of Sikkim and Arunachal Pradesh, falling in the Brahmaputra basin, experience snow cover. Brahmaputra river systems regions collectively are one of the greenest parts of India, accounting for the maximum 55.48% of the country’s forest cover. Majuli, an island, also a district of Assam, is known as the oldest and largest inhabited riverine island of the world, recognised by UNESCO.
• The hydroelectric potential of the Brahmaputra river systems has been assessed at 66065 MW. The Brahmaputra river, with a drop of elevation 4800 m, is achieved in a length of about 1700 Km in Tibet. This average slope of about 2.82 m/Km gets reduced to about 0.1 m/Km in Assam valley.
• Due to this sudden flattening of river slope, the river becomes braided in nature in the Assam valley. During its course in Assam valley from Kobo to Dhubri the river is joined by about 20 important tributaries on its North bank and 13 (thirteen) on its South bank, bringing high sediment load that results in braiding.
• All the tributaries of the valley area are rain-fed and foam up with rain, experiencing a number of flood waves as per rainfall in respective catchments.
• The precipitation here is mainly due to the South-West monsoon. Heavy precipitation occurs to the tune of 85% of total annual rainfall, only during the monsoon months from May to September. If the flood of the tributaries coincides with the flood of Brahmaputra, it causes severe problems and devastation.
• The region gets a good amount of rainfall in the months of April and May due to thunderstorm events, which account for flooding during heavy rain in June when the soil is already saturated and the river is in spate.

Brahmaputra River Tributaries

Moreover, six rivers—Tista, Sankosh, Raidak-I, Raidak-II, Torsa, and Jaldhaka—flow through northern West Bengal and ultimately merge into the Brahmaputra River in the plains of Bangladesh.

Siang River:

• Begins at the lofty Kailash Range, around 5300 meters above sea level.
• Flows eastward for approximately 1600 km through the Tibetan Plateau.
• Before entering India, passes through a deep gorge in the eastern Himalayas.
• Flows about 230 km in a south/south-easterly direction, reaching Pasighat.
• Lohit and Dibang rivers join 30 km downstream of Pasighat, forming the Brahmaputra.

Subansiri River:

• Originates in the mountains of Tibet.
• Total length is around 442 km, with 192 km in Arunachal Pradesh and 190 km in Assam.

Kameng or Jiabharali River:

• Rises from the unsurveyed hills of the Himalayas, possibly in Tibet.
• Flows 55 km in a south-westerly direction, ending its hilly journey at Bhalukpong.
• About 250 km, with 90 km in Arunachal Pradesh and 60 km in Assam.

Dhansiri (South) River:

• Rises in the southwest corner of Nagaland below Laishiang peak.
• Forms the boundary between Cachar, Nagaon, and Nagaland up to Dimapur.
• Flows through Karbi-Along and Golaghat districts of Assam, totaling nearly 354 km.

Kopili River:

• Begins in the Saipong Reserve Forest in the southeast of Meghalaya.
• Passes through Meghalaya, North Cachar hills, and Karbi Anglong before joining the Brahmaputra.
• 256 km, with 78 km forming the Meghalaya-Assam border and 178 km in Assam.

Manas River:

• Originates in Bhutan and enters Assam near Mathanguri.
• Splits into the Beki (eastern) and Manas (western) branches at Mathanguri.
• Meets the Brahmaputra near Jogighopa.

Teesta River:

• Rises in the Himalayas in North Sikkim.
• Runs through narrow gorges for approximately 138 km.
• Meets the plains of Jalpaiguri district.
• Joins the Brahmaputra near Rangpur town in Bangladesh after a journey of 309 km.

Characteristics of the Tributaries

North Bank Tributaries:

• These rivers on the north side have steep slopes and shallow, braided channels that extend quite a way from the foothills, sometimes reaching all the way to the outfall.
• The riverbeds are covered with boulders, pebbles, and coarse sand, and they carry a significant amount of silt.
• Floods in these tributaries tend to be sudden and intense, known for their rapid rise and fall.

South Bank Tributaries:

• On the south side, rivers flow with gentler gradients, forming deep, meandering channels right from the foothills.
• These rivers have a lower amount of silt in comparison.
• Floods in these tributaries are more predictable and less prone to sudden and drastic changes.

Conclusion

Brahmaputra River and its tributaries play a crucial role in the northeast region. However, there are significant challenges like erosion, frequent flooding, and damage to people’s livelihoods. Siltation, or the accumulation of sediment, is also a big issue. The river is vital not only for water security but also for potential impacts downstream, especially related to events in China. The lack of a proper mechanism and adherence to decisions for sharing important data on the river’s flow from upstream, as well as the construction of dams, are worrisome. This puts the region at risk of flooding, which could be entirely human-made due to the mismanagement of the river’s flow.

Read Also: Himalayan Drainage System