The Himalayas have been sending warnings that governments ignore at their peril. The massive rock-and-ice collapse near Langtang Lirung in Tibet-Nepal in August 2026, at around 5,000 metres, demonstrated how a geological event high in the mountains can unleash devastating floods downstream. Thousands died or remain missing.
Yet India appears ready for another massive intervention in this fragile mountain system. The proposed 11,200 MW Siang Upper Multipurpose Project (SUMP) in Arunachal Pradesh is being projected as a strategic necessity to counter China’s mega-dam at Medog. But can one Himalayan gamble be justified as protection against another? Interestingly, SUMP, conceived by the Congress-led UPA in 2008, now finds merit in its former critic, the BJP.
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The Langtang disaster in Tibet was not a conventional glacial lake outburst flood (GLOF). A huge mass of rock and glacier ice detached from the mountain, triggering a destructive cascade of debris and water through the Lhende Khola, Bhote Koshi and Trishuli river systems. Temporary river obstruction and the subsequent release of water magnified the devastation. A collapsing mountain slope can itself create a temporary dam and unleash a destructive surge.
The wider lesson is that the Himalayas are an interconnected and unstable ecological system. Both India and China are competitively ratholing the northern and southern Himalayas in the name of development. The consequences can travel far beyond the project sites.
The Aral Sea offers another warning. Soviet-era diversion of the Amu Darya and Syr Darya for irrigation progressively shrank one of the world’s largest inland water bodies. Its exposed seabed became the Aralkum desert, releasing salt and contaminated dust into the atmosphere. The consequences extended to Tibet and even Greenland.
China’s proposed 60,000 MW hydropower project, 5.5 billion cubic metre water, at Medog, at the Great Bend of the Yarlung Tsangpo in Tibet, has understandably alarmed India. The river enters Arunachal Pradesh as the Siang and subsequently becomes the Brahmaputra. Beijing’s control over this upstream project raises concerns about sudden water releases, withholding water during lean periods and the strategic leverage that control over river flows could provide.
India’s response is SUMP, an 11,200 MW project with approximately 9.2 billion cubic metres of proposed live storage. It is presented as a water buffer to regulate sudden upstream releases, moderate floods and generate electricity. But larger storage does not automatically guarantee protection. SUMP’s effectiveness would depend on available reservoir capacity when a flood arrives, incoming water volumes, warning time and release management. A sudden mountain collapse, water surge, rock and debris may overwhelm even a substantial reservoir.
If China’s intervention is considered dangerous because of the uncertainty and risks to downstream, India’s own intervention must face equally rigorous scrutiny.
The proposed dam lies in the seismically active Eastern Himalayas, where the continuing collision of the Indian and Eurasian tectonic plates creates unstable geological conditions. Earthquakes, active faults, landslides and heavy monsoon rainfall make the region particularly sensitive to large infrastructure projects.
Landslides or a major slope failure into the reservoir could displace water and generate destructive waves. Sediment from repeated landslides could undermine the purported storage capacity and undermine the project’s flood-moderation function. Upstream glacial instability adds to these uncertainties. Langtang has demonstrated how rock-and-ice collapse can generate a catastrophic surge. The October 2023 Teesta III disaster in Sikkim, when a glacial lake outburst flood overwhelmed hydropower infrastructure, should remain a warning. Expensive engineering cannot eliminate the forces of an unstable mountain environment.
The strongest opposition to SUMP comes from the indigenous Adi community, whose concerns deserve to be heard on their own merits. For the Adi people, the Siang is not merely a river offering hydropower potential. It is Ane Siang, Mother Siang, central to their cultural identity, ancestral memory, agriculture and everyday existence. The reservoir could submerge around 27 villages, with estimates of 32 or more facing varying degrees of impact. The actual number of affected settlements and households requires transparent, independent verification. But the implications go far beyond the number of houses requiring relocation.
The Adi economy and social life are closely linked to the river and its surrounding landscape. Terraced paddy fields, fishing, forests, traditional agriculture and community-managed resources sustain livelihoods. Sacred places, burial grounds, customary institutions and ancestral lands cannot simply be recreated at a resettlement site. Compensation may replace a house or landholding on paper; it cannot replace a community’s relationship with its river and territory.
Local organisations, including the Siang Indigenous Farmers Forum, oppose surveys without meaningful consent through traditional councils and village institutions. Their concerns are genuine. Police highhandedness can’t solve it. The October 23 violence at Pasighat is regrettable, but the underlying grievances need dialogue, not coercion.
The SUMP requires independent cumulative-impact and seismic-safety assessments, transparent disclosure and genuine consultation with the Adi people including their land rights, consent and rehabilitation concerns must be central, not peripheral.
The Himalayas are not an unlimited construction site. China may pursue its strategic ambitions, but India must not imitate its approach without considering the consequences. It needs to build world opinion against China. National security is not measured merely in megawatts or reservoir capacity. It is measured by the ability to protect people, preserve rivers and prevent avoidable disasters. The Siang must not become another Himalayan blunder.
INFA
