India must brace for what China builds on the Brahmaputra

The Brahmaputra originates in the Angsi glacier in Tibet and flows through China as the Yarlung Tsangpo before entering India’s Arunachal Pradesh. In Arunachal Pradesh, it is called Siang and Dibang and becomes the Brahmaputra in Assam and Bangladesh. During the lean season, the Yarlung Sangpo’s annual outflow from China is far lower than the Brahmaputra’s total discharge within India. Only about 30% of the water flow in the Brahmaputra comes from glacier melt and some rainfall in Tibet. The remaining 70% is fed by the Indian monsoon through its tributaries—Subansiri, Lohit, Kameng, Manas, Dhansiri, Jia-Bharali, Kopili, Krishnai, Digaru, and Kulsi—whose catchments are spread across the hilly regions of Arunachal Pradesh, Assam, Nagaland, and Meghalaya.

China is currently constructing the world’s largest hydropower project on the Yarlung Sangpo, with a capacity of 60 gigawatts, at an estimated cost of $137 billion. This is underway near the Great Bend in Tibet, close to India’s border.

India’s concern is not so much that the flow of water in the Brahmaputra will be depleted, but rather that once the dam is operational, the release of excess water could become a serious threat. Hydrologists warn that sudden releases—whether accidental, deliberate, or triggered by earthquakes—could cause devastating flash floods downstream, severely impacting Arunachal and Assam. Today, water disputes are increasingly driven by variability, which has become unpredictable in a warming world. We can no longer reliably forecast when and where cloudbursts or intense rainfall events might occur, with as much as 400 mm of rain falling in just 72 hours.

China has refused to join the 1997 UN Watercourses Convention and is not a party to any water-sharing treaty. In this context, India must prepare a science-based defence strategy. This includes creating and upgrading water storage structures, embankments, flood diversions, and expanding inland navigation infrastructure. At the same time, India must respect the ecological sensitivity and seismic volatility of the region. The Siang multipurpose project in Arunachal Pradesh was designed to safeguard against sudden release of water from China. However, it did not progress due to protests from environmentalists. The state must address the environmental concern and take this project forward. 

The Tibetan region and its fringe areas in China are seismically active. This is where the India and Eurasia plates clash, with a potential to cause uplifts and increase the height of the Himalayan peaks.

Despite seismic vulnerability, four more hydro projects--the Dagu dam (640 megawatt), the Zangmu dam (510 megawatt), the Jiacha dam (320 megawatt), and the Jiexu dam (300 megawatt), were planned in the upstream of Yarlung Sangpo, and only Zangmu is completed, and the remaining are marred by logistical and technical challenges due to steep mountains and deep gorges. A study presented at the Goldschmidt Conference in Prague recently concludes that as the planet warms, glaciers melt and retreat and release the downward pressure on earth’s crust and mantle. This, in turn, causes expansion of subterranean gases and magma, leading to pressure buildups fuelling explosive volcanic eruptions. As the glaciers retreat due to climate change, volcanic eruptions are going to be more frequent and explosive. 

The Indus Water Treaty (IWT) of 1960 had allocated the western rivers Indus, Jhelum, and Chenab to Pakistan and the eastern rivers Ravi, Beas, and Sutlej to India. Pakistan was authorised to use 80% of the water, and India only 20%. It was the most generous treaty favouring the lower riparian state, i.e., Pakistan. Many of India’s projects, like the Kishenganga and Ratle hydroelectric projects, could not take off owing to sustained objections from Pakistan. Since the treaty is suspended following the terror strike at Pahalgaon on April 22, India is taking action to expedite planning and execution of projects on western as well as eastern rivers. Uri Stage II, Kirthal-II, and Sawalkot power projects are listed for environmental clearance. It is now possible to execute work on the Tulbul navigation barrage in the Wullar Lake in North Kashmir for navigation in Jhelum. 

While Pakistan is bringing international pressure on India to revive IWT, the data from climate scientists reveal that the treaty in its present form should never be accepted. The glaciers located on the eastern side that feed water to the Sutlej, Beas, and Ravi rivers are at relatively lower altitudes as compared to the glaciers in the Karakoram mountain ranges that feed water to western rivers, namely the Indus, Jhelum, and Chenab. While glaciers at lower altitudes feeding eastern rivers are retreating, the high mountain ranges of Karakoram are not. The stability or the anomalous growth of glaciers in central Karakoram has defied the logic of climate change and is known as the ‘Karakoram anomaly’ in the scientific community. This would mean while the inflow in western rivers will remain constant, it would deplete in eastern rivers. India must get a larger share from western rivers too. 

(The writer is a retired principal chief conservator of forests—head of the Forest Force, Karnataka)

The views expressed above are the author's own. They do not necessarily reflect the views of DH.