Living rivers, dying rivers: Rivers in North East India

The fourth lecture in the ten-part series titled "Living Rivers, Dying Rivers" was delivered by Dr. Chandan Mahanta, Professor, Indian Institute of Technology Guwahati on 'Rivers in North-East India'.
The majestic Brahmaputra river (Source: Wikimedia Commons) The majestic Brahmaputra river (Source: Wikimedia Commons)

Rivers in North-East India

This lecture began with a broad overview of the general state of the North East and its river systems. The region comprising eight Indian states has a unique geo-strategic location for the reason that it is connected with mainland India through a narrow stretch of land and is surrounded by China, Myanmar, Bangladesh, Bhutan and Nepal. In spite of its rich natural resource endowment especially its water resources, the region faces neglect from the Indian state apart from challenges like contested ethnicities, political & social marginalities, widespread poverty, geographical disadvantage and armed insurgencies.

The rivers of the North East being hidden in the Himalayas are insufficiently studied, and the value of the massive river systems emerging from the Tibetan plateau--the water tower of Asia--is yet to be fully understood. The region with just five percent of the country’s area has thirty percent of the national water resource potential and its per capita water availability is 18,400 cubic meters as compared to the national figure of 2,208 cubic meters.

However, in spite of the large water potential, the region is caught in a paradox marked by the presence of some of the most water-starved pockets and bleak irrigation and agricultural development. Partial and uncertain accessibility of a water resource database has resulted in the lack of adequate scientific planning. Besides, water resources related institutional arrangements are bureaucratically complex and/or incomplete. 


Brahmaputra: Geo-strategic aspects

The focus of the lecture was on the Brahmaputra, bearing in mind that it is the real integrator of the diverse rivers of the North East. Also known as the lifeline of the region, it is a major international river with a drainage area of 580,000 square kilometers, 50 percent of which lies in China where it originates, 34 percent in India where it surges through Arunachal Pradesh and Assam, and 8 percent in Bangladesh which it finally touches before meeting the Bay of Bengal. Another 8 percent of its catchment area lies in Bhutan. The first 1,625 kilometers of the Brahmaputra lies in China, the next 918 kilometers in India, and the remaining 363 kilometers in Bangladesh.

The river’s origin in China makes it strategically important, more so now because it has plans to build a mega structure upstream of the Great Bend of the Yarlung Tsangpo (Brahmaputra in China) to divert water to the Gobi Desert and northern China. Because the river gains in volume only in India, to a certain extent India’s fears regarding reduced inflows can be put to rest at least for monsoon flows, though this may have a negative effect on the non-monsoon flows. Dr Mahanta mentioned that regional platforms encompassing basin countries are essential for discussing these critical trans-national river issues. 

Furthermore, there is a need to undertake mass balance studies to estimate the amount of water received by India from the Brahmaputra system and the subsequent outflow to Bangladesh. It is held that the highly porous piedmont zone in India may be contributing a lot of water to the deep groundwater systems of the region and that this is surfacing in the Brahmaputra floodplain in downstream Bangladesh. This needs to be corroborated through scientific studies.

Spurt in hydel power development in the North East

The Brahmaputra basin in India is shared by Arunachal Pradesh (42 percent), Assam (36 percent), Nagaland (6 percent), Meghalaya (6 percent), Sikkim (4 percent), and West Bengal (6 percent). Water conflicts have surfaced in this ecologically and seismologically sensitive region, which have witnessed several anti-dam movements in the recent past. There is a lot of resentment about the sudden burst of hydro-power prospecting and the numerous MoUs that are being signed in the region. The region possesses fortyfour percent of the country’s hydropower potential and it is widely felt that like tea and oil, energy too will be extracted from this hydel powerhouse by mainland India for 'national' growth.

The projects proposed in the Upper Brahmaputra--Arunachal Pradesh in particular--which has a hydel power potential of 60,000 MW, have led to discontent both from the local community which faces displacement, as well as downstream areas in Assam which will get reduced inflows. Damming of the Subansiri is expected to reduce the inflows in the Brahmaputra at Guwahati by ten percent.

Attempts by the other North Eastern States to bring Arunachal Pradesh to the table to create a North East Water Resource Authority have failed. Arunachal Pradesh has chosen a different trajectory in a bid to earn royalties from its vast hydropower potential and has instead created an Arunachal Pradesh Water Resource Authority.  

Dr. Mahanta steered clear of taking a dichotomous stance on the issue of big versus small dams. He highlighted the ecological consequences of these projects, as also the futility of damming the fast flowing rivers of the region that carry colossal volumes of water. The complex outcomes of displacement on the local communities, particularly on the several tribes whose numbers have depleted to a few hundred, was highlighted in the lecture. The enormous loss that wiping off a tribe has on the cultural diversity of the region was also discussed.

Problems faced

The Brahmaputra faces the world’s highest loss of channel gradient just before entering India (2500 m over a distance of only 200 kms). This is in the fragile young Himalayas comprised of unconsolidated sedimentary rocks marked by heavy erosion. As a result, this is the highest sediment load carrying river in the world. Lot of soft rocks and debris are carried by the fast flowing river which gets deposited on the way before reaching Bangladesh where it attains a sluggish pace.

The region is especially vulnerable to earthquakes, major landslides and floods, and unfettered dam development may have disastrous consequences. Wide-ranging deforestation and mining in the catchment has also added to the sedimentation problems. The sediment deposition in the downstream areas has led to a reduction of channel capacity resulting in catastrophic flooding.

The river is prone to channel migration and is a classic example of a braided river. To contain floods, simple interventions like constructing bamboo porcupines were perhaps better considering that junking the rivers with structural measures such as embankments have failed either because they are washed away or because of the changed natural flows and fragmentation of the river channels.

There are around 3500 wetlands along the Brahmaputra just in the Assam plains. Adjoining wetlands provide important nursery grounds for fish and export organic matter and organisms into the main channels. It is high time that we recognise that rivers are not merely moving masses of water but are in fact habitat to complex geomorphic, chemical and biological processes in motion. These habitat mosaics support a wide variety of aquatic and riparian species (including microbial parts, which are hardly recognised).

A river's ecological health and viability is its natural flow-regime. Natural variable flows create and maintain dynamics between the channel, floodplain, wetland and estuary. Variability is critical to ecosystem functioning and native biodiversity. Rivers with highly altered and regulated flows lose their ability to support natural processes. Dammed rivers are described by many as 'dead rivers'.

Water quality issues deserve particular attention because arsenic contamination of groundwater has been identified in the paleochannels of the Brahmaputra up till the foothills of the Himalayas posing serious health threats.

The impact of global climate change would appear earlier in this geo-environmentally vulnerable region with massive water and sediment load. Studies indicate that a rise in surface temperatures in the high Himalayas will lead to increased snow melt, resulting in greater incidence of flooding in rivers flowing from the Himalayan catchments.

Playlist :Rivers of North East India


In conclusion, Dr. Mahanta suggested the following effective development and management options:

  • Flood management and not just flood mitigation 
    • Improvement of existing measures;
    • Combination of various measures;
    • Flood plain zoning, flood proofing and flood forecasting;
    • Social changes in terms of innovative dwelling house and suitable occupation; and
    • Proper implementation of advanced technologies, e.g., geo-synthetic materials, amphibian mini dredger, hydraulic driving method.
  • Integrated inter-institutional R&D support
    • Overcoming inadequacy of scientific investigation;
    • Development of advanced instrumentation;
    • GIS-MIS based decision support systems;
    • Model simulation;
    • International expertise sharing; and
    • Digital Brahmaputra: a prototype Brahmaputra to model Brahmaputra.
  • Need of a renewed policy of Integrated Water Resource Management 
    • Overcome geopolitical challenges;
    • Appropriate policies, participatory processes, inter-state and international cooperation;
    • Specified roles of institutions and stakeholders groups;
    • Management tools that involve regulation, monitoring and enforcement;
    • Climate change issues too need to be integrated;
    • Provision of data by concerned departments and sharing of data among riparian states as well as countries for collective endeavor;
    • Country level discussion and consultation;
    • Strengthened mechanism for transparency, public participation, accountability;
    • Environmental flow maintenance, water rights; and
    • Development of a Brahmaputra River Conservancy Commission or an Authority like the one on the Yellow/Mississippi river.

The lecture was followed by a question answer session which touched upon issues related to water governance, problems associated with transfer of water from the Brahmaputra to the Ganga system and peninsular India, and adverse implications of hydel power development in the North East.

The lecture in various parts can be viewed on Youtube as listed below:

The lectures in the series can be viewed here:

India Water Portal is grateful to Prof. Ramaswamy Iyer for allowing it to record the lecture and share the videos online. 

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